Arctic Climate and Water Change:
Information Relevance for Assessment and
Adaptation
Arvid Bring
Department of Physical Geography and Quaternary Geology
Stockholm University
c Arvid Bring ISSN: 1653-7211
ISBN: 978-91-7447-638-5
Cover: Bank of the Ob River at Salekhard, Russia.
Layout: Summary: Arvid Bring based on a LATEX template by Rickard Petterson. Papers II and IV: Arvid
Bring using LATEX. Paper I: Wiley Blackwell. Paper III: Springer. Paper V: AGU. Reprinted with permission.
Doctoral dissertation 2013 Arvid Bring
Department of Physical Geography and Quaternary Geology Stockholm University
Abstract.The Arctic is subject to growing economic and political interest. Meanwhile, its water and climate systems are in rapid transformation. Relevant and accessible infor-mation about water and climate is therefore vital to detect, understand and adapt to the changes. This thesis investigates hydrological monitoring systems, climate model data, and our understanding of hydro-climatic change, for adaptation to water system changes in the Arctic. Results indicate a lack of harmonized water chemistry data, which may impede e↵orts to understand transport and origin of key waterborne constituents. Further devel-opment of monitoring cannot rely only on a reconciliation of observations and projections on where climate change will be the most severe, as they diverge in this regard. Climate model simulations of drainage basin temperature and precipitation have improved between two recent model generations, but large inaccuracies remain for precipitation projections. Late 20th-century discharge changes in major Arctic rivers generally show excess of water relative to precipitation changes. This indicates a possible contribution of stored water from permafrost or groundwater to sea level rise. The river contribution to the increasing Arctic Ocean freshwater inflow matches that of glaciers, which underlines the importance of con-sidering all sources when assessing change. To provide adequate information for research and policy, Arctic hydrological and hydrochemical monitoring needs to be extended, better integrated and made more accessible. This especially applies to hydrochemistry monitoring, where a more complete set of monitored basins is motivated, including a general exten-sion for the large unmonitored areas close to the Arctic Ocean. Improvements in climate model parameterizations are needed, in particular for precipitation projections. Finally, fur-ther water-focused data and modeling e↵orts are required to resolve the source of excess discharge in Arctic rivers.
Keywords: Arctic, hydrology, monitoring, climate change, water management, general cir-culation models, adaptation.
Svensk sammanfattning
Arktis ¨ar f¨or n¨arvarande f¨orem˚al f¨or ett tilltagande intresse, b˚ade fr˚an ekonomiskt och poli-tiskt h˚all. Samtidigt genomg˚ar den arktiska regionen snabba och genomgripande f¨or¨andringar i klimat och milj¨o. Dessa f¨or¨andringar kommer inte bara att p˚averka Arktis, utan ocks˚a ge upphov till l˚angtg˚aende globala e↵ekter.
Vatten har en central roll i m˚anga av de mest uppm¨arksammade f¨or¨andringar som nu ob-serveras. Som exempel kan n¨amnas den kraftigt minskande utbredningen av sommarist¨acket i Norra ishavet, och den tinande permafrosten i delar av Sibirien och Alaska. I och med vattnets sammanl¨ankande roll ¨ar det av stor vikt med relevant och tillg¨anglig information om f¨or¨andringar i vatten och klimat.
I denna avhandling unders¨oks hydrologiska ¨overvakningssystem och data fr˚an globala klimatmodeller f¨or Arktis, med avseende p˚a v˚ar f¨orst˚aelse f¨or de f¨or¨andringar som nu p˚ag˚ar och v˚ar f¨orm˚aga att anpassa samh¨allet till dem. Resultaten visar bland annat p˚a en brist av sammanst¨allda och j¨amf¨orbara vattenkemiska data f¨or de floder som rinner ut i Norra ishavet. Detta kan f¨orsv˚ara f¨ors¨ok att f¨orst˚a hur ¨amnen transporteras i Arktis, och vad deras ursprung ¨ar.
F¨or att prioritera en utveckling av vatten¨overvakningen beh¨ovs robust information om vilka omr˚aden som kommer att ber¨oras mest av f¨or¨andringar i klimatet. I det h¨ar avseendet pekar dock observationer och modeller i olika riktningar, vilket g¨or att det inte tillf¨orlitligt g˚ar att identifiera s¨arskilt utsatta omr˚aden dit ¨overvakningen b¨or prioriteras.
Globala klimatmodellers projektioner av temperatur och nederb¨ord har f¨orb¨attrats mel-lan tv˚a successiva generationer av modeller, men stora avvikelser finns fortfarande i deras simuleringar av nederb¨ord. ¨Aven om nederb¨ordsprojektionerna skulle bli mer noggranna finns det andra sv˚arigheter i att ¨overs¨atta nederb¨orden till prognoser f¨or f¨or¨andringar i vat-tenfl¨odet. Under senaste delen av 1900-talet har ett antal stora arktiska floder n¨amligen upp-visat ett ¨overskott p˚a vatten i j¨amf¨orelse med de f¨or¨andringar som observerats i nederb¨ord. Detta indikerar ett m¨ojligt bidrag fr˚an grundvattenf¨orr˚ad eller permafrost till floderna, och en f¨orb¨attrad f¨orst˚aelse beh¨ovs f¨or dessa komplexa samband i vattensystemet.
Under de senaste decennierna har s¨otvatteninfl¨odet till Norra ishavet ¨okat, b˚ade fr˚an floder, glaci¨arer och den gr¨onl¨andska inlandsisen. ¨Okningen av fl¨odet fr˚an floderna ¨ar av samma storleksordning som ¨okningen i glaci¨aravsm¨altning, vilket understryker vikten av att ta h¨ansyn till alla k¨allor n¨ar man s¨oker en fullst¨andig f¨orst˚aelse av f¨or¨andringarna.
F¨or att bidra med b¨attre information f¨or forskning och policybeslut beh¨over ¨overvak-ningen av vattensystemet i Arktis f¨orst¨arkas. En b¨attre integration mellan olika system och databaser skulle bidra till ¨okad tillg¨anglighet och ¨overblick. Detta g¨aller i synnerhet f¨or vattenkemi, d¨ar stora omr˚aden n¨ara Norra ishavet idag ¨ar helt o¨overvakade. F¨or att f˚a en mer representativ bild av f¨or¨andringarna beh¨over sammans¨attningen av de avrinnings-omr˚aden som ¨overvakas ocks˚a bli mer helt¨ackande. Vad g¨aller klimatmodeller kr¨avs en fort-satt f¨orb¨attring, i synnerhet av hur nederb¨ord simuleras. Det ¨ar ocks˚a motiverat med yt-terligare anstr¨angningar som fokuserar p˚a vattendata och modellering av vattensystemet, f¨or att f¨orst˚a ursprunget till ¨overskottet p˚a vatten i arktiska floder.
Arctic Climate and Water Change: Information Relevance
for Assessment and Adaptation
Arvid Bring
This doctoral dissertation consists of this summary and the following papers, which are referred to by their roman numbers in the text.
I Bring, A. & Destouni, G., 2009. Hydrological and hydrochemical observation status in the pan-Arctic drainage basin. Polar Research 28, 327–338. II Bring, A. & Destouni, G., 2013. Hydro-climatic changes and their
moni-toring in the Arctic: Observation-model comparisons and prioritization options for monitoring development. Accepted for publication in Jour-nal of Hydrology.
III Bring, A. & Destouni, G., 2011. Relevance of hydro-climatic change projec-tion and monitoring for assessment of water cycle changes in the Arctic. Ambio 40, 361–369.
IV Bring, A. & Destouni, G., Manuscript. Evaluation of IPCC AR4 climate model performance over 14 major Arctic watersheds. Appendix to Paper III.
V Dyurgerov, M.B., Bring, A. & Destouni, G., 2010. Integrated assessment of changes in freshwater inflow to the Arctic Ocean. Journal of Geophys-ical Research 115, D12116.
The co-authorship of the papers reflects the collaborative nature of the underlying research. For Papers I–IV, I was responsible for all analysis and had the main re-sponsibility for designing the study and writing the paper. For Paper V, I had the main responsibility for the design, analysis and writing of the river component of the paper, and contributed to the interpretation and writing of the remainder of the paper.
Other related peer-reviewed publications by the author:
Karlsson, J.M., Bring, A., Peterson, G.D., Gordon, L.J. & Destouni, G., 2011. Opportunities and limitations to detect climate-related regime shifts in in-land Arctic ecosystems through eco-hydrological monitoring. Environmental Research Letters 6, 014015.
Rennermalm, ˚A.K., Bring, A. & Mote, T.L., 2012. Spatial and scale-dependent controls on North American pan-Arctic minimum river discharge. Geograph-ical Analysis 44, 202–218.
Jarsj¨o, J., Asokan, S.M., Prieto, C., Bring, A. & Destouni, G., 2012. Hydrological responses to climate change conditioned by historic alterations of land-use and water-use. Hydrology and Earth System Sciences 16, 1335–1347.
Abbreviations
AHC Arctic Hydrological Cycle AR4 Fourth Assessment Report AR5 Fifth Assessment Report CRU Climate Research Unit GCM General Circulation Model GRIS Greenland Ice Sheet
IPCC Intergovernmental Panel on Climate Change MG&IC Mountain Glaciers and Ice Caps
PADB Pan-Arctic Drainage Basin
SAON Sustaining Arctic Observation Networks SRES Special Report on Emission Scenarios TAR Third Assessment Report
Introduction
A multitude of global-scale changes, including cli-mate change, are currently transforming the Earth system. This is clearly evident in the Arctic, where temperatures over the last half-century have in-creased at a rate 50% higher than the Northern hemi-sphere average (McBean et al., 2005), and where future climate change is expected to be most pro-nounced (Kattsov et al., 2005). Coupled to the changes in the physical environment, the Arctic is also increasingly becoming a focal point of economic and geopolitical interest.
These transformations present a considerable challenge. The critical role of the Arctic in the global climate system implies that Arctic changes will have far-reaching consequences for, and feedbacks to, the Earth system (McGuire et al., 2006). To understand the changes, and to the degree possible, adapt to them, is therefore of large importance to the global community.
Water is a key integrating, propagating and reg-ulating factor, and therefore plays a central role in the changing Arctic and the wider global climate system. It is a shared component in the most im-portant and recognized Arctic indications of global change. These indications include rapidly diminish-ing extent of sea ice (Comiso et al., 2008; Stroeve et al., 2012a), increased mass loss from glaciers (Kaser et al., 2006; Gardner et al., 2011), increasing river flows (Peterson et al., 2002; 2006; McClelland et al., 2006; Shiklomanov & Lammers, 2009; Overeem & Syvitski, 2010) and increasing groundwater con-tribution to those flows (Smith et al., 2007; Lyon and Destouni, 2010), permafrost degradation (Hinz-man et al., 2005; White et al., 2007; Brutsaert and Hiyama, 2012), ecosystem regime shifts (Smol et al., 2005; Karlsson et al., 2011), and shorter extent of snow cover season (Brown et al., 2010; Callaghan et al., 2011).
In order to observe, assess and plan for adapta-tion to the changes to the Arctic Hydrological Cycle (AHC) over the Pan-Arctic Drainage Basin (PADB), it is vital that observation systems and models can provide adequate information of relevance to sci-entists, environmental managers and policymakers. The importance of data and observation systems in particular has recently been emphasized at intergov-ernmental summits (GEO, 2010) and recognized as one of five ”grand challenges” for Earth system sci-ence and scisci-ence policy over the next decade (Reid et al., 2010; ICSU, 2010).
Assessing previous and ongoing change in the wa-ter system requires observations of river discharge,
as well as sediment and water chemistry data to estimate the waterborne mass fluxes of important global cycle constituents such as carbon, nitrogen and phosphorus. The collection of such hydrologi-cal and hydrochemihydrologi-cal data is normally conducted through continuous monitoring programs by various government agencies.
However, in many countries, hydrological obser-vation systems have been in decline during recent decades. The extent of monitoring generally peaked around 1980, after the significant increases in mon-itoring e↵orts during the International Hydrological Decade 1965–1974. Since then, budget constraints and failure to maintain existing systems have re-sulted in a general decline of monitoring, which has been reported in several studies (Brown, 2002; Fekete & V¨or¨osmarty, 2002; Maurer, 2003; Hannerz, 2008; FAO, 2009).
The global trend of declining discharge moni-toring is also evident in the Arctic (Lammers et al., 2001; Shiklomanov et al., 2002; Hinzman et al., 2005; Walsh et al., 2005, Arctic-HYDRA consortium, 2010). However, the particular situation in the Arc-tic has received relatively much attention in the sci-entific community, partly due to the rapid changes and the general scientific interest in the region. Also, the accessibility to discharge data has been improved more in the Arctic than in many other parts of the world, due to concentrated international e↵orts and collaborations, in particular at the University of New Hampshire.
In contrast to discharge monitoring, a clear pic-ture of the status of water chemistry data for that discharge has been lacking. Previous e↵orts have tried to establish a status for particular parame-ters (e.g., Holmes et al., 2000; Holmes et al., 2002; Raymond et al., 2007), and estimated the quality of existing data (Zhulidov et al., 2000; Holmes et al., 2001; Zhulidov et al., 2003). Although partic-ular data sets have been made accessible for parts of the PADB (e.g., Holmes et al., 2000; Holmes & Peterson, 2002), and in at least one case for the wider PADB (McClelland et al., 2008; data at http://www.arcticgreatrivers.org), no international repository and data host exists for all accessible Arc-tic water chemistry data. Neither has any initia-tive yet been launched to develop a common set of indicators, such as the Millenium Development Goals-related UN Federated Water Monitoring Sys-tem (FWMS) and its Key Water Indicators Portal (KWIP).
The decline in station numbers and the lack of integrated hydrological and hydrochemical informa-tion, together with the grand challenge of improving Earth observation systems, constitute an imperative 1
ARVID BRING
to develop Arctic hydrological monitoring networks, and to ensure their relevance under conditions of cli-mate change. To formulate a rational strategy to im-prove monitoring in the Arctic, one then either has to rely on some degree of certainty in the distribu-tion of future changes, or acknowledge that other po-tential bases for prioritization may exist and try to harmonize them. Despite its importance for robust improvement of monitoring networks, this question has so far received little attention.
To address this problem, and also the direct adaptation-central issue of projecting present and past hydro-climatic changes to the future, relevant and robust climate data are required. The primary information basis for global climate projections is the Intergovernmental Panel on Climate Change (IPCC) ensemble of general circulation models (GCMs), which form the basis for the IPCC assessment re-ports. The two most recent reports are the Third Assessment Report (TAR; 2001) and the Fourth As-sessment Report (AR4; 2007). The fifth report (AR5) is scheduled for release in 2013.
The performance of GCMs in the Arctic has been the subject of intensive discussion. Assessments of TAR and AR4 model performance in the Arctic have shown improvements between successive generations of models, but also indicated that significant short-comings remain in simulating observed climate pa-rameters (Christensen et al., 2007). There have been several assessments of simulations of sea ice processes (Zhang & Walsh, 2006; Overland & Wang, 2007; Stroeve et al., 2007; Eisenman et al., 2007, Holland et al., 2010, Stroeve et al., 2012b), the surface ra-diation budget (Sorteberg et al., 2007, Bo´e et al., 2010) and surface temperature (Lui et al., 2008) over the Arctic Ocean, while there are fewer studies ex-plicitly examining GCM performance related to hy-drological components of the Arctic hyhy-drological cy-cle over drainage basin scales. Kattsov et al. (2007) analysed the output of the AR4 model ensemble for four major basins in the PADB, and Roesch (2006) evaluated AR4 simulations of snow cover. Holland et al. (2007) investigated ten AR4 GCMs to estimate change in freshwater budget of the Arctic Ocean, in-cluding pan-Arctic scale runo↵, and Rawlins et al. (2010) used the same GCMs combined with reanaly-sis and observational data in a pan-Arctic analyreanaly-sis of Arctic hydrological cycle intensification. However, no basin-wise investigation and comparison of GCM re-sults between the TAR and AR4 has been performed for a larger set of basins within the PADB, and no benchmark of AR4 GCM performance over such a set of basins exists for comparison with the upcom-ing AR5 set of models.
Climate data Water flow data Water information Glacier change data Paper I Paper III
Paper IV Paper II
Paper V
Figure 1. Integrative links between water information
and other components of climate and water change un-derstanding. Connections investigated in this thesis are shown with arrows, which are colored according to the ap-pended papers where the analyses are carried out. Poten-tial subsequent assessment and adaptation applications that derive from water information, and apply to the understanding of changes across other terrestrial, atmo-spheric and marine systems, are illustrated with dashed arrows.
Assessment of AHC change, including projection of hydro-climatic system changes to the future, is central to adaptation. It has also been a question of considerable scientific interest in the recent decades. Component studies and integrative system assess-ments (e.g., V¨or¨osmarty et al., 2001; Serreze et al., 2006; Slater et al., 2007; Rawlins et al., 2009; 2010) have greatly improved understanding of the AHC, but several inconsistencies, understanding gaps and open questions remain (Arctic-HYDRA consortium, 2010).
The importance of the water system in Arctic and global change implies that the hydrological drainage basin is a fundamental and relevant unit of scale, both for water management, adaptation and basic re-search (Pahl-Wostl, 2007; UNECE, 2009). This the-sis links and analyses several components required to provide reliable water information for change adaptation and assessment (Figure 1), consistently at drainage basin scales. This basscale water in-formation and understanding then also has impor-tant ensuing applications in understanding coupled 2
ARCTIC CLIMATE AND WATER CHANGE
changes across other terrestrial, atmospheric and ma-rine systems (e.g., Karlsson et al., 2011), illustrated in Figure 1 by dashed arrows from the water infor-mation box.
The thesis is centered on the following two over-arching research questions:
1. Are current surface water system observations representative, accessible and relevant for as-sessing changes to the Arctic environment and connections to global systems? What critical gaps and key limitations exist, and is there a basis to robustly prioritize how to address these limitations?
2. Are climate model results and our understand-ing of water budget changes in major Arctic basins and the wider pan-Arctic ocean drainage system sufficient for adaptation of society to cli-mate and other global change?
Methods and data
The hydrological drainage basin has been the funda-mental basis when investigating the research ques-tions of this thesis. The drainage basin constitutes a physically consistent boundary for closing the flow balance of water and the mass balances of constituents transported by water, which makes it a relevant scale for addressing both scientific and management-related problems.
The study area of the thesis is centered on the 14 largest Arctic watersheds in the PADB, cover-ing an area of at least 200,000 km2 each and with a
combined drainage of 13.8 million km2 (see map of
study area in Figure 2). These basins are common to the analysis in Papers II–IV. In Paper I, the entire PADB is included. For paper V, the analysis focuses on the central Arctic Ocean drainage, a subset of the PADB, and includes 17 basins, of which 11 are in common with the 14 major basins and the remainder are smaller ones. Paper V also separately incorpo-rates mountain glaciers and ice caps (MG&IC) that contribute water directly to the Arctic Ocean, as well as the Greenland ice sheet (GRIS). Figure 3 shows the characteristic temperature and precipitation con-ditions, and recent observed changes for those pa-rameters, in the 14 major basins.
Basin-scale climate data in the form of observa-tions and GCM projecobserva-tions were analyzed for the 14 major basins in Papers II–IV. Papers III and V con-tain synthesis and analysis of discharge data for the basins included in the respective studies. Paper I also includes a characterization of basin properties based
Watersheds included Papers II-V Papers II-IV Paper V Remaing PADB Glaciers (Paper V) MG&IC GRIS 180° 120°W 60°W 120°E 60°E 0° Ma Ob Ye Le Ko Ne Yu Pe SD Ol Kh Ch Ya In
Figure 2. Map indicating studied areas of the PADB.
Basins common to Papers II–V are shown in red, and ad-ditional studied basins in blue (Papers II–IV) and green (Paper V). Paper I includes all areas within the PADB, demarcated by the combined area of all colored basins and the dark gray area. The glaciers (crosses) and the GRIS (light blue) are also included in Paper V. Basin names are abbreviated as Ne: Nelson, Ch: Churchill, Ma: Mackenzie, Ko: Kolyma, Kh: Khatanga, Ol: Olenek, Le: Lena, Ya: Yana, In: Indigirka, Ye: Yenisey, SD: Severnaya Dvina, Pe: Pechora, and Yu: Yukon. Lambert azimuthal equal-area projection; approximate scale 1:150 000 000.
on a range of data sources, and Paper V includes analysis of glacier change data.
Climate observation data were in the form of global gridded datasets of temperature and precipita-tion at half-degree resoluprecipita-tion. For paper III, the Cli-mate Reseach Unit (CRU) TS 2.1 dataset (Mitchell & Jones, 2005) was used, and for Papers II and IV both the CRU TS 3.10 (Harris et al., in review) and the Willmott & Matsuura 3.1 (method first described in Willmott & Matsuura, 1995; data available at http://climate.geog.udel.edu/ climate) datasets were used. For climate projections in Papers II–IV, IPCC TAR (Paper III only) and AR4 global climate model 30-year means from the IPCC data distribution cen-ter (http://www.ipcc-data.org) were used.
ARVID BRING
Figure 3. Climate characteristics of the 14 major
Arc-tic basins. The top panel shows average annual tempera-ture; the bottom one shows annual average precipitation, for the periods 1961–1990 and 1991–2009. Data from CRU (Harris et al., in review) and Willmott & Matsuura
(http://climate.geog.udel.edu/⇠climate).
For Papers III and V, discharge data from the R-ArcticNET (Lammers et al., 2001) and ArcticRIMS (http://rims.unh.edu) databases were used. Paper V also includes discharge data from the Water Survey of Canada HYDAT database (Environment Canada, 2004).
Glacier data in Paper V consist of data on an-nual direct mass balance observations carried out for MG&IC (Dyurgerov & Meier, 2005; Glazovsky & Macheret, 2006; Fluctuations of Glaciers (FoG), 2008), and of several recent modeling studies for the GRIS (Rignot et al., 2008; Hanna et al., 2008, 2009; Box et al., 2006; Mernild et al., 2009).
Summary of papers
Paper IBring, A. & Destouni, G., 2009. Hydrological and hydrochemical observation status in the pan-Arctic drainage basin. Polar Research 28, 327– 338.
Paper I presents a synthesis of all accessible discharge and water chemistry data for the PADB, with lists of data sources and specifics of each data set. The extent of accessible data is further presented in map form, illustrating the maximum length of time series and latest data year for the PADB. Characteristics of monitored and unmonitored areas are summarized for, and compared between, North America, Europe and Asia.
The general picture derived from the analysis in Paper I shows a considerable di↵erence between ac-cessible water chemistry monitoring and discharge monitoring, both in terms of total extent and char-acteristics of the data. In general, discharge data are available for a wide range of di↵erent basins, from small catchments of a few square kilometers in size to the major river basins in the PADB. In contrast, accessible water chemistry monitoring is limited to a much smaller set of stations, which cover a signif-icantly smaller area and also a much less complete range of basin sizes.
Figure 4 shows a summary of the accessible length of time series for discharge, sediment and car-bon monitored areas. The average length of time se-ries for the various parameters, and the correspond-ing share of the PADB that is monitored, is further summarized in Table 1.
Table 1. Average length of time series and monitored
share of total area for discharge, carbon and sediment data in the PADB.
Parameter Average timeseries Area length (years) monitored
Discharge 29 73%
Sediment 7 63%
Carbon 5 51%
Results from Paper I also show a marked di↵er-ence in characteristics of monitored and unmonitored areas (Figure 5). For example, monitored areas are distinctly dominated by the taiga eco-region, while unmonitored areas are generally strongly defined by tundra type vegetation. This tendency is particularly evident for discharge monitoring in all regions, and for all monitoring parameters in Asia. The most bal-anced monitoring, in terms of eco-region proportions, 4
ARCTIC CLIMATE AND WATER CHANGE
b
1 - 10 11 - 20 21 - 40 41 - 70 71 - partly monitoredunmonitored or not accessible
c
a
Figure 4.Overview of the maximum length of accessible data series (years) for the pan-Arctic monitoring
of (a) water discharge, (b) sediment, and (c) carbon. Cells containing stations with drainage areas smaller than five cells are indicated as partly monitored.
Figure 5. Distribution of terrestrial eco-regions in monitored (M) and unmonitored (U) areas, by
moni-toring parameter and continent.
is for carbon monitoring in Europe, while the most unbalanced monitoring is found in North America and Asia. Such regional monitoring di↵erences com-plicate the interpretation of observation data di↵er-ences between di↵erent parts of the PADB.
Paper II
Bring, A. & Destouni, G., 2013. Hydro-climatic changes and their monitoring in the Arctic: Observation-model comparisons and prioritiza-tion opprioritiza-tions for monitoring development. Ac-cepted for publication in Journal of Hydrology.
In this paper we analyze the prioritization basis for planning of monitoring development under condi-tions of climate change. We formulate two alternate final stages of possible climate change in the next half-century by selecting the five warmest or wettest models from the most severe IPCC Special Report on Emission Scenarios (SRES) scenario (A2), and the five coldest or driest models from the least severe scenario (B1). For these two cases, we analyze the relative distribution of climate change severity across the 14 largest Arctic drainage basins, and compare this distribution with hitherto observed changes.
ARVID BRING Nelson Churchill Mackenzie Kolyma Khatanga
Olenek Lena Yana Indigirka Yenisey
Ob
S.Dvina Pechora Yukon
1 2 3 4 5 6 K Temperature change Nelson Churchill Mackenzie Kolyma Khatanga
Olenek Lena Yana Indigirka Yenisey
Ob
S.Dvina Pechora Yukon
0 50 100
mm!yr Precipitation change
Observations Cool!dry B1 Warm!wet A2
Figure 6. Changes to temperature (left) and precipitation (right) from 1961–1990 to 1991–2009 for
ob-servations and to 2040–2069 for GCM projections across 14 major Arctic basins. Error bars indicate one standard deviation of di↵erent GCM results from the model ensemble mean for each basin.
Results from Paper II indicate that observations and projections of climate change severity across the pan-Arctic are not in agreement, when comparing the relative order of basins (rank correlations of basin orders are close to zero, or negative; Table 2). Both directional (in the case of precipitation) and tempo-ral shifts are required to bring observed changes in line with projections (Figure 6). Some continued di-rectional changes are naturally expected, however, as observations and projections concern di↵erent time periods.
In Paper II, we also analyze how the present dis-tribution of hydrological monitoring network density relates to observed and projected climate change. Re-sults from this analysis show that current network density is more adapted to prioritize monitoring ca-pacity for the so far observed precipitation changes than the observed temperature changes, or the pro-jected future changes in either temperature or pre-cipitation.
Table 2.Spearman’s correlation of GCM-projected
cli-mate change ranking with observed clicli-mate change rank-ing. Scenario ⇢ Scenario ⇢ Temperature Precipitation Cool B1 0.01 Dry B1 -0.10 Hot A2 -0.03 Wet A2 -0.23 Paper III
Bring, A. & Destouni, G., 2011. Relevance of hydro-climatic change projection and monitor-ing for assessment of water cycle changes in the Arctic. Ambio 40, 361–369.
Paper III first presents a comparison of IPCC TAR and AR4 GCM projections for precipitation and temperature in the 14 largest Arctic basins. Area-weighted basin average projections were summa-rized and compared with observed changes. Paper III results also include a comparison of precipitation-discharge changes for the studied basins, as well as an analysis of the evolution of the discharge-monitoring network in relation to projected climate changes.
Figure 7 illustrates GCM projections and CRU observations for the 14 major basins. Temperature projections seem compatible with observed changes during the late 20th and early 21st century, both for the TAR and AR4, while precipitation projections in-dicate an increase that is hitherto not evident in ob-servations. The absolute GCM results compare well with observations for temperature, but the models considerably overestimate precipitation.
A further result of Paper III is that the responses in discharge to changes in precipitation vary widely for the major basins in the PADB (Figure 8). The majority of basins exhibit excess flow changes in rela-tion to precipitarela-tion changes; that is, discharge has so far increased more (or decreased less) than precipita-tion within each basin. These disagreements between precipitation and discharge changes are in some cases large; therefore, an essential question for forthcom-ing investigation is: where does the extra water come from?
Finally, Paper III presents an analysis of the de-velopment of the discharge monitoring system in re-lation to projected climate change. A comparison of monitoring station density between the period of peak extent of monitoring and a recent period shows that the weight of discharge monitoring sys-tems has shifted towards the basins where the ex-6
ARCTIC CLIMATE AND WATER CHANGE Ê Ê ‡ ‡ Ï Ï 1961-1990 1991-2002 2010-2039 -8 -6 -4 -2 Temperature H° C L Ê Ê ‡ ‡ Ï Ï 1961-1990 1991-2002 2010-2039 400 500 600 700 800 Precipitation Hmm êyr L Observations AR4 models TAR models
Figure 7. Changes to temperature (left) and precipitation (right) from 1961–1990 to 1991–2002 for
ob-servations and to 2010–2039 for GCM projections across 14 major Arctic basins. Error bars indicate one standard deviation of di↵erent GCM results from the model ensemble mean.
ARCTIC CLIMATE AND WATER CHANGE
⇥
⇥
⇤
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1961 1990 1991 2002 2010 2039 8 6 4 2Temperature
°C
⇥
⇥
⇥
⇤
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1961 1990 1991 2002 2010 2039 400 500 600 700 800Precipitation
mm
⇤yr
⇥
Observations AR4 models TAR modelsFigure 7. Changes to temperature (left) and precipitation (right) from 1961–1990 to 1991–2002 for observations and to 2010–2039 for GCM projections across the 14 major Arctic basins. Error bars indicate one standard deviation of di↵erent GCM results from the model ensemble mean for each basin.
40 20 0 20 50 0 50 Precipitation change mm yr 1⇥ Runoff change mm yr 1 ⇥ Ch In Ko Le Ma Ne Ob Ol Pe SD Ya Ye Yu 1:1 line R 2⇥0.46
Figure 8.Changes from 1961–1990 to 1991–2002 in ob-served annual average precipitation and corresponding runo↵ for 13 major Arctic basins. The dashed line indi-cates a 1:1 change in precipitation and runo↵. The solid line is a linear best-fit regression of actual changes in all basins except the Ch (Churchill) watershed, which is af-fected by major artificial water diversions. Abbreviations of basin names are the same as in Figure 6.
Paper IV
Bring, A. & Destouni, G. Manuscript. Evaluation of IPCC AR4 climate model performance over 14 major Arctic watersheds. Appendix to Paper III.
Paper IV is an appendix to and extension of the analysis made in Paper III. Here, we perform an ex-plicit error and performance analysis of IPCC AR4 GCMs over the 14 largest Arctic watersheds. Mean Absolute Error (MAE), Mean Bias Error (MBE) and a dimensionless index of model performance (dr;
Willmott et al., 2012) are evaluated against observa-tions of temperature and precipitation for the refer-ence period of 1961–1990. We also analyze the cor-relation between ranking of model performance for temperature and precipitation simulations.
Results from this analysis indicate that there is a large spread in error and relative performance be-tween the models forming the basis for the AR4 (Fig-ure 9). For some basins, and for the pan-Arctic in general, an above-average model performance in tem-perature simulation does not correlate particularly strongly with performance in simulating precipita-tion (MAE and dr rank correlations negative; Table
3). This implies that choosing a ”best” model is dif-ficult if one wants to have consistently good perfor-mance in simulating both parameters over the Arctic.
Table 3. Spearman rank correlation coefficient ⇢ be-tween the pan-Arctic temperature and precipitation val-ues of MAE, MBE and dr.
⇢MAE ⇢MBE ⇢dr
-0.29 0.37 -0.29
7
Figure 8.Changes from 1961–1990 to 1991–2002 in
ob-served annual average precipitation and corresponding runo↵ for 13 major Arctic basins. The dashed line indi-cates a 1:1 change in precipitation and runo↵. The solid line is a linear best-fit regression of actual changes in all basins except the Ch (Churchill) watershed, which is af-fected by major artificial water diversions. Abbreviations of basin names are the same as in Figure 2.
pected changes to temperature and precipitation are the smallest. If one aims to follow up and capture the actual e↵ects of climate change on the AHC, this is not a desirable development.
Paper IV
Bring, A. & Destouni, G. Manuscript. Evaluation of IPCC AR4 climate model performance over 14 major Arctic watersheds. Appendix to Paper III.
Paper IV is an appendix to and extension of the analysis made in Paper III. Here, we perform an ex-plicit error and performance analysis of IPCC AR4 GCMs over the 14 largest Arctic watersheds. Mean Absolute Error (MAE), Mean Bias Error (MBE) and a dimensionless index of model performance (dr;
Willmott et al., 2012) are evaluated against observa-tions of temperature and precipitation for the refer-ence period of 1961–1990. We also analyze the cor-relation between ranking of model performance for temperature and precipitation simulations.
Results from this analysis indicate that there is a large spread in error and relative performance be-tween the models forming the basis for the AR4 (Fig-ure 9). For some basins, and for the pan-Arctic in general, an above-average model performance in tem-perature simulation does not correlate particularly strongly with performance in simulating precipita-tion (MAE and drrank correlations negative; Table
3). This implies that choosing a ”best” model is dif-ficult if one wants to have consistently good perfor-mance in simulating both parameters over the Arctic.
Paper V
Dyurgerov, M., Bring, A. & Destouni, G., 2010. Integrated assessment of changes in freshwater inflow to the Arctic Ocean. Journal of Geophys-ical Research 115, D12116.
ARVID BRING
Figure 9.Mean Absolute Error (MAE; top panel), Mean
Bias Error (MBE; middle panel) and model performance
index (dr; bottom panel) for 14 GCMs across the PADB.
In this paper we perform an integrated analysis of freshwater inflow to the Arctic Ocean, and sepa-rately assess the contribution of rivers and glaciers to this inflow over the period 1961–2006. We specif-ically investigate the periods 1961–1991 and 1992– 2006, where the break coincides with a shift in mag-nitude of glacier mass loss (Lemke et al., 2007).
Results from this assessment are generally in line with other studies that indicate an increase in fresh-water inflow to the Arctic Ocean. However, our anal-ysis also highlights that the magnitude of the in-crease in inflow from the 1961–1991 to the 1992– 2006 period is similar for the river contributions and the glacier contributions (Figure 10). This underlines the importance of also accounting for river discharge
Table 3. Spearman rank correlation coefficient ⇢
be-tween the pan-Arctic temperature and precipitation
val-ues of MAE, MBE and dr.
MAE MBE dr ⇢ -0.29 0.37 -0.29 1960 1970 1980 1990 2000 -500 0 500 1000 1500 2000 2500 year C u m u la ti ve d e vi a ti o n fr o m 1961 -1992 mean Hkm 3 L MG&IC GRIS Rivers
Figure 10.Above: Total meltwater runo↵ and total river
runo↵ into the Arctic Ocean. Below: Cumulative devia-tions in annual freshwater flows from MG&IC, GRIS, and rivers relative to average values for 1961–1992.
changes that are not related to glacial melt water changes as a potentially contributing source for sea-level rise and the freshening of the Arctic Ocean wa-ters.
Discussion
Robust scientific understanding of climate and water systems is a prerequisite for informed policy deci-sions in assessing and adapting to the large-scale en-vironmental changes currently transforming the Arc-tic and other regions. This in turn requires access to relevant information on changes to flows of water and waterborne constituents. This thesis has aimed to contribute to a more complete picture of sev-eral important components required for AHC change monitoring and adaptation planning. This has been done by investigating two overarching research ques-tions pertaining to the adequacy and information rel-evance of water monitoring systems, and of climate model and hydro-climatic change understanding, for change assessment and adaptation.
ARCTIC CLIMATE AND WATER CHANGE
Regarding the first research question on the rele-vance of hydro-climatic data, the results from Papers I–III point to some important shortcomings, but also to certain opportunities and results of relevance for future research and monitoring improvement e↵orts. The synthesis of monitoring data in Paper I in-dicates a lack of water chemistry data, compared with the more extensively accessible discharge data. The range of basin sizes, sampling frequency, and length of time series for water chemistry data over-all compare negatively with corresponding attributes for discharge data. Together, these shortcomings im-ply that the full potential of translating the existing discharge data to also calculate mass fluxes of im-portant constituents is hindered.
Furthermore, the di↵erence in characteristics of monitored areas found in Paper I indicate that ex-isting monitoring data are not representative of the PADB as a whole. This constitutes a limitation to the value and reliability of the modeling that must be used for interpreting and projecting changes in the AHC in unmonitored areas.
From the perspective of an integrative pan-Arctic analysis, the limited accessibility to water chemistry data is remarkable, given the high profile of and international commitment to research into Arctic environmental changes. While discharge data have been compiled into pan-Arctic datasets (most im-portantly, R-ArcticNET (Lammers et al., 2001) and the ARDB (http://ardb.bafg.de)) and also made ac-cessible in near-real time through the ArcticRIMS project (http://rims.unh.edu), water chemistry data remain fragmented, although the recent continuation of the PARTNERS project as the Arctic Great Rivers Observatory (http://www.arcticgreatrivers.org) con-stitutes an important improvement.
Several factors may explain these results. Firstly, although the research community emphasizes a sys-tem perspective on the pan-Arctic domain, no ternational body has formal responsibility for an in-tegrated monitoring system. Instead, monitoring ef-forts must build upon undertakings by separate gov-ernment agencies in at least the eight di↵erent na-tions of the Arctic Council, and for hydrology also Mongolia and Kazakhstan, which constitute parts of the PADB. Even if all national hydrometeorologi-cal agencies were committed to promoting a coordi-nated Arctic observation e↵ort, domestic budget lim-itations and conflicting information goals may still interfere with ambitions being met.
Secondly, public agencies that apply cost-recovery principles to their environmental data may be reluctant to undermine this rule by freely sharing their data with international repositories. Thirdly, in a previously isolated Arctic that is now rapidly
becoming more accessible to activities such as natu-ral resource exploration, shipping and tourism, water data may be viewed as increasingly sensitive informa-tion from both political and economic perspectives. Occasionally, pressure from international organiza-tions on member states to disclose water chemistry information viewed as sensitive has rebounded and instead caused delays in the progress of sharing other water data (Vladimir Ryabinin, personal communi-cation).
All the same, member states of the Arctic Council have in the Tromsø Declaration recently committed to facilitate data access, as a legacy of the Inter-national Polar Year during 2007–2009. The organi-zational form for this commitment is the Sustaining Arctic Observation Networks (SAON) process, which is currently in its implementation phase. The Eu-ropean Commission has also expressed support for SAON (European Commission, 2008; 2012). It re-mains to be seen to which extent the SAON process can contribute to increased accessibility to monitored water chemistry data in the PADB, but it is now es-tablished as a platform for policy dialogue on Arc-tic monitoring issues, for example through recurring Arctic Observation Summits.
Whether through institutional pan-Arctic initia-tives or through other channels at various levels and scales, any remediation of the present-day monitor-ing system shortcommonitor-ings identified in Paper I re-quires a strategy to improve observation networks under conditions of climate change. This issue is in-vestigated in Paper II, which centers on the priori-tization of hydro-climatic change monitoring across the Arctic.
Improvements of monitoring and observing ca-pacity in the Arctic, and elsewhere, must incorporate climate change projections in order to take the non-stationary nature of the environment into account (Milly et al., 2008). For the case of the Arctic, how-ever, results from Paper II indicate that the relative distribution of climate change severity, as simulated by GCM projections, does not agree with the distri-bution of actually observed changes across the major Arctic basins, which places obstacles for a robust pri-oritization strategy based on reconciliation of obser-vations and projections for an assessment of which basins that will be most a↵ected by climate change. An alternative strategy to the aforementioned one could be to prioritize basins where the disagree-ment between observations and projections is partic-ularly large, as such a strategy would yield impor-tant information on the hydro-climatic system func-tioning and changes regardless of whether there is actual convergence of observations and projections in the end or not. Alternatively, one could argue 9
ARVID BRING
for prioritizing monitoring of basins with greater ob-served changes so far, as these are actual experienced changes where increased e↵orts at understanding and adaptation can be intrinsically motivated. Such a pri-oritization is to some degree evident in the present distribution of monitoring, specifically with respect to precipitation changes, although this situation is most likely not by design but by coincidence.
The divergent rationales and prioritization bases that can be argued for based on the results of Paper II underline the importance of attempting to formu-late win-win or no-regret solutions in any strength-ening of hydro-climatic monitoring e↵orts under cli-mate change conditions (UNECE, 2009), incorporat-ing also other relevant parameters, in addition to the temperature and precipitation data studied here, and explicitly identifying set information goals to be achieved. The results presented here can inform ob-servation assessments connected to strategic Arctic initiatives and programs, such as SAON and the up-coming Third International Conference on Arctic Re-search Planning (ICARP III) in 2015, where contin-ued evaluation of monitoring e↵orts will be a priority. The second research question about climate model and water budget change understanding is explored in Papers III–V. Paper III highlights im-provements in basin-scale climate model simulation of temperature and precipitation, but also identi-fies some key remaining limitations, which are fur-ther examined in Paper IV. Also in Paper III, some challenges to water system understanding through the precipitation-discharge change relation are pre-sented, and Paper V extends the discharge assess-ment of these changes to a full Arctic Ocean freshwa-ter inflow synthesis, including a glacier-independent river change component in addition to the change contributions from melting glaciers, ice caps, and the Greenland ice sheet.
Considerable improvements have been made be-tween the two successive generations of model en-semble runs that underlie the most recent IPCC As-sessment Reports, the TAR and the AR4. Examples include improved parameterization of land surface schemes and snowpack, as well as the inclusion of canopy processes in most models (Randall et al., 2007). However, important uncertainties remain in the representation of cryospheric feedbacks, which explain part of the range of model responses at mid and high latitudes (Randall et al., 2007).
These improvements are evident in that Paper III results indicate a lower spread among the ensemble members for the AR4 models, and in the case of pre-cipitation, a marked improvement in the agreement with absolute observed values. However, despite the improvement in precision, accuracy remains
insuffi-cient for precipitation projections, which, even if they were correct, are still difficult to translate to sub-sequent changes in the water cycle without further and finer resolved hydrological modeling. It should be noted that observations also are associated with uncertainty, for example gauge undercatch of primar-ily solid precipitation due to wind (e.g., Yang et al., 2005; Tian et al., 2007), which may explain part of the remaining di↵erence between observations and the improved AR4 results. Based on a global pre-cipitation bias adjustment by Adam & Lettenmaier (2003), the annual e↵ect seems generally to be about 10–25% over the latitudes of the whole PADB, but may amount to higher values in the most northern parts of some basins.
The large span in model performance, evident from the explicit error and performance analysis of AR4 models in Paper IV, also indicates that large uncertainties and shortcomings remain for re-liable simulations of hydro-climatic parameters on basin scales. The analysis furthermore underlines that models may yield good output results on these scales for the wrong reasons. For example, the pan-Arctic bias error of both temperature and precipita-tion for the GIER model is close to zero, which would place it at the top of a basin-scale simulation perfor-mance ranking. At the same time, the absolute error and the performance index for the same model are among the worst of the ensemble, implying large de-viations from observations at individual grid points, even though the deviations happen to almost can-cel out across the PADB. Overall, the evaluation in Paper IV can serve as a benchmark for evaluating the performance change against the subsequent gen-eration of climate models, which underlies the forth-coming IPCC AR5 report.
Notwithstanding further improvement in GCM simulations, full understanding of hydro-climatic change, and transfer of this understanding back into model development, requires basin-scale understand-ing of precipitation-discharge change patterns. In the Arctic, certain counterintuitive hydro-climatic changes have caused intense investigation and discus-sion in the scientific community. The fact that most of the rivers analyzed in Paper III can be termed so-called ”excess” rivers (that is, the increase in dis-charge has been greater than the increase in precip-itation) is consistent with findings by Milliman et al. (2008) for a related set of Arctic rivers. This, and other studies (e.g., Dyurgerov & Carter, 2004; McClelland et al., 2006; Smith et al., 2007; Lyon et al., 2009; Brutsaert & Hiyama, 2012) indicate that both specific climatic and subsurface processes per-taining to the Arctic, such as permafrost degrada-tion, as well as other anthropogenic changes, and 10
ARCTIC CLIMATE AND WATER CHANGE
general atmospheric patterns such as increased mois-ture transport from outside the PADB, are responsi-ble for the range in discharge patterns, but the rela-tive importance of the di↵erent contributing factors is not definitely established. Undercatch of snow, in combination with increases in winter precipitation (Bulygina et al., 2009; Rawlins et al., 2009), is also a potential contributing factor. The wide spread in discharge responses to precipitation changes indicate a need for further concerted modeling and field in-vestigation e↵orts aimed at increasing the process knowledge of hydrological regimes particular to the Arctic domain, including simulations of evaportran-spiration and permafrost processes, considering also e↵ects of scale (Rennermalm et al., 2012). Improved parameterization, in particular with precipitation fo-cus, is also critical to the development of GCMs, and continued water-balance assessments and closure ex-periments in Arctic catchments are motivated.
The extended water budget changes of the en-tire PADB and its Arctic Ocean drainage including glacier contributions, studied in Paper V, also has implications for global climate system changes, and sea level rise influencing both the Arctic region and the wider Earth system. The fact that increases in river freshwater contribution are of the same order of magnitude as increases from MG&IC and GRIS un-derlines the importance of accurately understanding the reasons for river flow changes, and the potentially contributing components of frozen and liquid water storage changes in major Arctic basins (e.g., Mus-kett & Romanovsky, 2009). Such changes could have large implications on the pan-Arctic hydro-climatic system, but also on scales beyond the Arctic through contribution to sea level rise or thermohaline circu-lation functioning.
The review of literature and analysis in this the-sis confirms a picture of advances in our knowl-edge about the Arctic environment and its func-tioning during recent decades. International ef-forts at making discharge information accessible, e.g. through the ArcticRIMS project, have con-tributed to a more timely access to river flow data for a number of important basins and sub-basins. Similarly, the PARTNERS monitoring campaign (http://ecosystems.mbl.edu/partners), now semi-permanently established as the Arctic Great Rivers Observatory (http://www.arcticgreatrivers.org) has provided a multi-season dataset of concentrations of a range of important water chemistry constituents for six major Arctic rivers. Climate model advances have improved in precision and alignment with obser-vations in the Arctic, and numerous studies have con-tributed to a fuller understanding of hydro-climatic changes. These developments, which coincide with a
time of increasing focus on the Arctic as an arena for important changes, imply improvements also in our ability to understand the AHC and the associated PADB.
Nevertheless, considerable challenges for under-standing and managing the rapidly changing Arctic water system still remain. A critical priority must be to continue improving the accessibility to water data, in particular for water chemistry, for the PADB. Ob-servations must be made at the right places, and im-provements should be based on clearly stated infor-mation goals, striving in their achievement for win-win and no-regret approaches that do not rely on a single most likely scenario of future hydro-climatic conditions. Improved coverage of unmonitored areas in the northern rims of the PADB is also motivated, particularly as these areas are expected to become in-creasingly accessible and also subject to exploration with a warming climate (Andreeva, 1998). In addi-tion, improved monitoring here may yield informa-tion on the unclear role of these areas in the total flux of water chemistry constituents to the ocean, as near-ocean catchments have in other regions been shown to contribute an unproportionately large share of coastal pollution in relation to the drainage basin as a whole (Destouni et al., 2008).
Conclusions
This thesis has investigated the adequacy of water flow and water chemistry observations and climate model projections in the PADB, with the purpose of establishing a quantitative picture of the status of these observations and model results for under-standing and management of water cycle changes in the Arctic. The main findings of the thesis can be summarized in the following conclusions:
• There is a lack of long-term and accessible water chemistry data for large regions of the PADB, and discharge data is also limited for consider-able areas. The data that are accessible do not constitute a representative sample of the PADB environment.
• There is a need to extend monitoring and to make data more accessible, in particular for the relatively unmonitored but large areas on the northern rim of the Eurasian continent.
• Establishing regional priorities for hydrological monitoring systems with regard to the specific issue of climate changes in the Arctic can cur-rently not be achieved based solely on a recon-ciliation of observations and projections. When 11
ARVID BRING
taking di↵erent data and system/change per-spectives as starting points, di↵erent conclusions about what constitutes rational priorities, and related strategies, arise.
• The precision in predicting precipitation and temperature change on drainage basin scales has improved between successive generations of the IPCC model ensemble. However, that im-provement is relatively unimportant next to the large inaccuracy that still remains in pre-cipitation projections. Individual model perfor-mance varies greatly, and models can be right for the wrong reasons when relatively large er-rors cancel out on basin scales for some mod-els. Further investigation and benchmarking of model performance in the GCMs underlying the IPCC AR5 could indicate whether certain hydro-climatological model shortcomings in the Arctic have been addressed.
• Hitherto observed changes in precipitation do not translate into similar changes in discharge even over the large scales of the studied basins. The discrepancy between precipitation and dis-charge changes, and the fact that this discrep-ancy principally is expressed as excess in dis-charge compared to available precipitation, in-dicate that a component of the variation in dis-charge may be due to changes in permafrost or groundwater storage.
• Even though the increase in river inflow to the Arctic Ocean during 1993–2006 is small in rel-ative terms compared to the average flow for 1961–1992, in absolute terms it is of the same order of magnitude as the meltwater increase from glaciers, which underlines the importance of also accounting for river discharge changes as a potentially contributing source for sea-level rise and Arctic Ocean freshening.
Financial support
The research in this thesis has been funded through grants from the Swedish research council Formas (project number 2007-1263) and the Swedish Re-search Council (VR; project number 2007-8393), and has been linked to the Bert Bolin Centre for Cli-mate Research (in turn supported by VR and Formas through a Linneaus grant) and the strategic research project EkoKlim at Stockholm University. I grate-fully acknowledge travel support from the Graduate Research School of the Bolin Centre, C F Liljevalchs foundation, Knut and Alice Wallenbergs foundation,
L & E Kinanders foundation, John S¨oderbergs foun-dation, the government of the Yamalo-Nenets Au-tonomous Okrug, and the Arctic Research Council of the U.S.
Acknowledgements
I am very grateful for the invaluable support I have had from my main advisor, Georgia Destouni. With-out your insight, enthusiasm and guidance, Gia, this thesis would not have come about. You have always had time for extensive comments and feedback on my work, and I appreciate all the discussions we’ve had, on the specific research issues at hand but par-ticularly also on the larger picture, strategic science matters and science-policy interactions.
I have also much appreciated collaboration and discussions with my co-supervisors Jerker Jarsj¨o, Steve Lyon, Garry Peterson, and with my co-authors Johanna M˚ard Karlsson, Line Gordon and Mark Dyurgerov. Sadly Mark passed away too soon, be-fore we had an opportunity to continue our col-laboration. ˚Asa Rennermalm I would like to thank for stimulating discussions at my first international scientific meeting in Washington, DC, and the col-laboration that followed. A special thanks to Johan Kuylenstierna for introducing me to the world of in-ternational environmental negotiations. I would also particularly like to thank Fredrik Hannerz, Christof-fer Carstens and Klas Persson for many enjoyable lunches with inspiration on water-related topics.
I’ve always enjoyed going to work at the Depart-ment of Physical Geography & Quaternary Geology. Thanks to everyone for your contribution to a stimu-lating work environment. A particular thanks to the technical and administrative sta↵, who are invalu-able in keeping things together, and to the whole community of PhD students, past and present, for the support and discussions. Unfortunately I have been able to join all too few pub nights!
I also want to acknowledge the interdisciplinary group for environmental science PhD students. The atmosphere at our gatherings really stimulated an academic discussion, and remains one of my best memories from the doctoral studies at Stockholm University. I am very glad for the continued network that we have established, and for the perspectives on my research you have given.
The Association of Polar Early Career Scientists (APECS) also played an important role during my PhD studies. Stina and Sussie got me involved with APECS and have continued to be good friends and colleagues. Thanks to you and all other wonderful 12
ARCTIC CLIMATE AND WATER CHANGE
APECS people I have had the opportunity to get to know and work with.
To my sisters and brother, Nina, Torun, Hedda and Johan, and all other friends, thank you for the important support and encouragement. I would also like to thank my parents Lena and Axel. Your eru-dition remains a paragon to me, and I can only hope that age shall endow me too with some sagacity.
Since I started work on this thesis, I have had two wonderful sons, Valter and Tage. The two years I spent at home with them I would not trade for any career outcome in the world. But I have been away, too, particularly at conferences around the world. At these times, my wife Eva has had much support from my parents-in-law Helena and Weine, for which I (and Eva) are very grateful.
And to Eva, with whom I’ve shared ten wonder-ful years and hope to share many more, thank you, above all—for all the days, of love, light and joy.
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