The conditions of the seas around Sweden: Report from the activities in 1993

SMHI

RO

No 20, 1994

THE CONDITIONS OF THE SEAS

AROUND SWEDEN

Report

of

the activities in 1993

SMHI HYDROGRAPHIC STATIONS

•

Frequent statton

•

Mopping statton

•

•

I

•

•

•eus3

•

•

e • F26

•

•

• BY29

•

esv10

•

BCS 111-10

•

•

•

51111111

REPORTSOCEANOGRAPHY

THE CONDITIONS

OF THE

SEAS AROUND SWEDEN

Report

of

the activities in 1993

Lars Andersson, Bjom Sjoberg and Mikael Krysell

SMHI, Oceanographical laboratory, Goteborg Byggnad

31

Nya Varvet

S

-

426 71

Vostra Frolunda

lssuing Agency SMHI S-601 76 Norrkoping SWEDEN Author(s) Report number Report date

Lars Andersson, Bjom Sjoberg and Mikael Krysell

Title (and Subtitle)

RO No. 20 November 1994

The conditions of the seas around Sweden - Report of the activities in 1993

Abstract

This report describes some basic aspects of the hydrographical conditions in the open sea areas around Sweden, based on SMHls environmental monitoring program during 1993. A new monitoring program has been implemented, consisting of two types different types of stations. First, frequent stations wl?ich are few but have a high samp-ling frequency making it possible to resolve annual variations. Secondly mapping stations visited only a few times per year as to asses, oxygen conditions in the Kattegat and the Baltic deep waters and the pool of nutrients during the pre bloom season. The most interesting event during 1993 was the large inflow of salt water to the Baltic that occured in the beginning of the year. As a result the deep water in the East Gotland Basin was renewed and oxygenated for the first time since 1978.

Keywords

Baltic Sea, Skagerrak, Kattegat, Baltic monitoring Program, oceanography, temperature, salinity, oxygen conditions, hydrogen sulphide, nutrients

Supplementary notes

ISSN and title

0283 - 1112 SMHI Reports Oceanography

Report available from:

-SMHI Oceanographical Laboratory Building 31, Nya Varvet

S -426 71 Viistra Frolunda, Sweden

Number of pages

39

Language

CONTENTS Page 1. Introduction ..... 1 2. W eather a.nd lee Conditions ...... 1 3. Oceanographic Conditions ... 5 3.1 Skagerrak ... 5

3.2 Kattegat and the Sound ... 11

3.3 The Baltic Sea ... 18 3.4 The Gulf of Bothnia ... 27

4. The major inflow to the Baltic ...... 31

4.1 General hydrographic conditions of the Bal tie ... 31

4.2 The stagnation period preceding in the inflow ... 32

4.3 The inflow ... 32

4.4 Long term effects ... 36

5. Ack.nowledgement ... 36

Appendix Quality assurance ... 37

1.

Introduction

This report describes the hydrographical conditions in the open sea ares around Sweden

during 1993. The results are derived from data collected within SMHis environmental

rnonotoringprogram.

SMIIl Oceanographical Laboratory is carrying out a comprehensive investigationg activity in the open seas around Sweden, from the Skagerrak. to the northern most part of Bothnian Sea. The objectives are;

- to persistently and fora long term collect hydropgraphical data of known quality

in order to faciliate studies of climatic change, including human influence on the marine invironment

-to annualy account for oceanographical events of importance especialy the water

exchange between the Kattegat and the Baltic and the oxygen conditions in the

bottom waters of southern kattegat and southwestem Baltic Proper.

-to produce and deliver oceanographical data and reports nationally and intemationally especially to the swedish NSEP A, the National Board ofFisheries, HELCOM, IOC and ICES

During 1993 the laboratory has implemented a new sampling strategy anda new monitoring

program. The new program consist essentially of two types of stations, frequent and

mapping stations. At frequent stations we try to attain a high samping frequency as to

resolve annual variations within different subareas. Mapping stations are only visited few

times per year as to asses, the oxygen situation in the south of Kattegat and in the Baltic Proper and the pool of nutrients during winter.

The single most important event during 1993 was the large inflow of salt water from Kattegat to the Baltic in the beginning of the year. The first major inflow since 1977 ! As

an effect of the inflow the deep water in the Gotland Bassin was renewed and oxygenated

for the first time since 1978.

2.

Weather and ice conditions

The beginning of 1993 was characterized by strong winds, mild weather with surface

water ternperatures well above mean.

In

April there was a quick change from cold spring

to high summer temperatures, one can in fact say that the summer 1993 occurred already in May. During June the weather became more unstable and the wanning of the sea ceased. The weather during the rest of the summer continued to be relatively cold and

unstable, and the sea surface temperatures dropped below normal values. October was the

fifth consecutive month with both air and water temperatures below mean. The cooling of

the sea stopped however, and in November the surface temperature was again back to

Deviation from mean air temperature

6-.---

- - - -

- -

- - - ,

5 4 3 2 1 0 -1 -2 -3 ~---.----.---,---,---,---.----.---,----,----,.---,---,,---' 40 20 -20 -40 1 2 mm 1 2

~

Vinga 3 3 4 5 6 7 Month 8 9 10 11 12

Deviation from mean precipitation

4 5 6 7

Month

I

Gotska Sandlin

8 9 10 11 12

I

Bjurciklubb

Figure 2.1 Deviation from mean air tempera/ure and deviation from mean

precipitation at three different stations, Vinga on the west coast, Gotska Sandon in the Ba/tie and Bjuroklubb at the coast of the Bothnian Bay.

Deviation from mean run-off % 500 400 Fylleån 300 200 100 0 -100 1 2 3 4 5 6 7 8 9 10 11 12 Month % 500 400 _Anundsjon 300 200 100 0 -100 1 2 3 4 5 6 7 8 9 10 11 12 Month

Figure 2.2 Deviationfom mean runojf, Fylleån in the southwestern, and Anundsjon in the northeastern part of Sweden.

For the sixth consecutive winter the ice conditions were very easy. However, the ice started to develop very early but the freezing process stopped. Toen the ice extent really started to grow in early February and reached its maximmn in the end of the month when the Bothnian Bay and the Quark were coverd with ice. In March the ice drifted over to the Finnish side of the Bothnian Bay and the water was relatively open at the Swedish coast. The ice drifted back to the Swedish coast in early April and there was even a developmet of new ice. The weather became warmer in mid April and the ice started to melt and in late May the waters were completely ice-free.

MAXIMAL ISUTBREONING 24/2 1993 Mycket lindrig isvinter

Very easy ice winter

..

.,, .,

.,

3.

Oceanographic conditions during 1993

3.1 Skagerrak

In the beginning of April, the conditions were normal for the season in the whole area. During late summer and early autumn the surface water was colder than normal, while the

salinity was higher than the mean for the years 1981 to 1990. However, in the southeastern part the surface water was clearly influenced by the outflow from Kattegat and the situa-tion more variable. In the surface layer in the central area nutrient concentrasitua-tions were slightly below mean during the whole year (April-December). Along the coast of Jylland

all nutrients, and especially silicate showed very low values during summer and autumn.

STATION M6 SURFACE WATER

20

Tem peraiure ·c Salinhy psu

40 35 15 30 •••G••-~-•-C>•••CL •• ·D"···a . 10 25 20 5 _·-a.. -.. cf. 15 0 10 1 2 3 4 5 8 7 a 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

0 llYCCD ml/I P04 µmol/I

10 1.25 a

_·-

o--·D---. 1.00 a .75 ••• Q, 4 ,50 · ... b 2 . 25 ·•

.

..

0 o.oo 1 2 3

'

5 a 7 a 9 10 11 12 1 2 3 4 5 a 1 a 9 10 11 12

DIN µmol/I S101 µmol/I

30 30 25 25 20 20 15 15 10 _.-Q. 10

.

a. 5 5 ·v ... .., . .a ... ..• .a _{···a. ...}

...

.... ... a 0 ... 0 1 2 3 4 5 a 1 a 9 10 11 12 1 2 3 4 5 a 7 a 9 10 11 12

To1-N µmol/I Tot•P mol/I

40 2.0 35 30 1.5 25 20 .•• o. •.• a. ... 15 1.0 __ ... _Q 10 .5 5 0 0.0 1 2 3 4 5 a 7 8 9 10 11 12 1 2 3 4 5 a 7 8 9 10 11 12 MONTH MO NTH

Figure 3.1.l Monthly mean values 1993, solid line, compared to the mean annua/ cyclefor the years 1981-1990, dotted line. Station M6 in central Skagerrak.

STATION HS5 SURFACE WATER 20 Temperature "C 15 10 5 i:>··· 0 1 2 3 4 5 li 7 8 9 10 11 12 Oxygen ml/I 10 8 0, •••

..

8 ... •·0 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 DIN 30 µmol/I 25 ~ 20 15 10 5 0 1 2 3

'

5 8 7 8 9 10 11 12 Tot-N µmol/I 40

---=---~

35 30 25 20 15 10 5

./

ri

...

u···· a.,.-___ -ti,.:..-<:o... 0 ....j... _ _ _ _ _ _ _ _ _ _ .,... _ _ ....,..__,_.,...-,l 1 2 3 4 5 li 7 8 9 10 11 12 MONTH Salinity psu 40 35 ... ···•·•··· 30 25 20 15 10 1 2 3 4 5 8 7 8 9 10 11 12 PO, µmol/I 1.25 1.00 ~\ .75

\

.50 .25 0.00 1 2 3

'

5 8 7 8 9 10 11 12 Si0₁ µmol/I 30 25 20 15 10 5 0 ···0-···0 1 2 3

'

5 8 7 8 9 10 11 12 Tot-P mol/I 2.0 ---...::.;:.;...;_....c;.:.::.;;.;;..;.. _ _ _ _ , 1.5 1.0 .5 0.0

-1---..-....-...

- r - - 1 1 2 3 4 5 8 7 8 9 10 11 12 MONTH

Figure 3.1.2 Monthly mean values 1993, solid line, compared to the mean annua[

cycle for the years 1981-1990, dotted line. Station HS5 in southem

STATION P2 SURFACE WATER Temperature •c 20 - , - - - , 15 10 5 ·••0-•·•a. ••. 0 -t--,.--,,--.,...,...,...,.-,--.,...,...,.._ 1 2 3 4 5 8 7 8 Sl 10 11 12 10 _ _ _ _ _ _ 0_1_y_g_c_a_m_1n _ _ _ ____, 11 8

'

2 0 -+-... --.-..---,--,----,,--,,--..---,-...,..--1 1 2 3 4 5 8 7 8 9 10 11 12 DIN flmoUI 30 - - - , 25 20 15 10 ••• .ei. ••• 5 ·t:1, •• ,0, ..••. 0-••· ···o ... o. ... . 0 -l--,-...,...-!?-q,-~~-;,,-'jli::::::;~.---l 1 2 3 4 5 8 7 8 Sl 10 11 12 40 ...,... _ _ _ _ _ T_o_1-_N ___ µ_m_o_UI _ _ _ _,, 35 30 25 20 1$ 10 5 0 -+---.---.-..--...--.----.--,,--...--,--,---1 1 2 3 4 5 8 7 8 9 10 11 12 MONTH Saliaity pau 40 . . . , . . . - - - , 35 30 25 20 15 10 -t--,.--.-._-...,..--,.--,,--,--....,...-,--1 2 3 4 5 8 7 8 Sl 10 11 12 PO, flmoUI 1~5 - , - - - , 1.00 .75 ••• Q. •• ··o\ .50 \ \ .25 ti., -~---,o ...•...•. 0.00 ,4-...,..--,...:~~*==ljt==i~~..,... ... ~ I 2 3 4 5 8 7 8 9 10 11 12 SiO₂ µmoUI 30 - , - - - , 25 20 15 10 ···a. 5 ••••· ••• 0

+--r-~~~,8:,-~~e::=~

1 2 3 4 5 8 7 8 9 10 11 12 Tot-P moln 2.0 ...,... _ _ _ _ ...;..;..;_;;...._..i;.a;;..;;.;;;.;;._ _ _ ..., 1 .5 1.0 .5 _.P.._

..

· ·

..

• ..b_ ····o .... ... a•-··· 0.0 -+--,.-.---.--....-... . -1 2 3 4 5 8 7 8 9 10 11 12 MONTH

Figure 3.1.3 Monthly mean values 1993, solid line, compared to the mean annual cycle for the years 1981-1990, dotted line. Station P2 in southeastem Skagerrak.

The temperatures in the Skagerrak deep water, 400 m, was about 0.5 degrees

above mean most of the year. The oxygen concentration and the amount of

dis-solved inorganic nitrogen DIN (DIN=NO₂+NO₃+NH₄) were higher than normal while

the concentration of phosphate was slightly below mean. In the deep water, 75 m,

in the southeastern part the concentrations of silicate and phosphate were below

normal during the period May to December, while DIN concentrations were close

STATION M6 DEEP WATER

Tempera.ture oC Salinity psu

20 40 15 35 ·••0-••C> •-30 10 25 5 ... a. ... o-··· ··•o-•.. o-··· ... 20 15 0 10 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12

Oxygen mUI PO, µmol/I

10 1.25 8 1.00 ···a···a.·- ... a .. 8 .•. Q--•0-··· _{····o-•-·-·--·-•·0···} .75 4 .50 2 .25 0 o.oo 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12

DIN µmol/I SiO1 µmol/J

30 30 2S 25 20 20 1S 15 • a-.. . 0 --0----0 8: 0 .0 ... _.0 ••.•••• 10 _{.• a. •.• o-···0-•··0-··-··· ···-·-···-··0··} 10

.·

..

..

s 5 _{G·-•a a-···} ...

-···•-o---0 0

1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12

40 Tot-N µmol/I 2.0 Tot-P mol/I

35 30 1.S 25 _{... a. ... ····-···0 ..} 20

-···

1.0 o---o. ... a-···O-··· 1S 10 .5 5 0 0.0 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 s 8 7 8 9 10 11 12 MONTH MONTH

Figures 3.1.4 Monthly mean values 1993, solid line, compared to the mean annua[

cycle for the years 1981-1990, dotted line. Station M6 in central Skagerrak.

STATION HSS DEEP WATER Tcmperauire •c 20 15 to 5

···-~

...

0 t 2 3

..

5 8 7 8 9 10 tt 12 Ollygen ml/1 10 8 8 ··-···••0-··· .. 4 2 0 1 2 3

..

5 8 7 8 9 10 t t 12 DIN µmol/I 30 25 20 t5 to 5 0 1 2 3 4 5 8 7 8 9 10 11 12 Tot-N µmol/I 40 - - - , 35 30 25 20 15 10 5 0 _.,_ _ _ _ _ ...,..__,_..,...,...,.--,-.,...-1 1 2 3 4 5 8 7 8 9 10 1 t 12 MONTH 40 Salinity p111 35 ···••0-••· 30 25 20 15 10 1 2 3

..

5 8 7 8 9 10 11 12 PO, µmol/I 1.25 1.00 .75 _···-a.

··

.

. 50 .25 o.oo 1 2 3 4 5 6 7 8 9 10 11 12 SiOl µmol/I 30 25 20 15 10 5 ···•-O. ... _{···0···· ···•-C} 0 1 2 3 4 5 8 7 8 li 10 11 12 Tot-P mol/I 2.0 ... - - - , 1.5 1.0 .5 •••••• ••• Q. ···a ····0-•••0-··-.,.··,._·· - ~ 0.0 +--,-,---,--,---,-.,...-r--.-.r--r-""1 1 2 3 4 5 8 7 8 li 10 11 12 MONTH

Figure 3.1.5 Monthly mean values 1993, solid line, compared to the mean annua/

cyclefor the years 1981-1990, dotted line. Station HS5 in southem

STATION P2 DEEP WATER Temperaiun: -C 20 -15 0 ~ - - . - - . - -... ---.-....-... - - . - - ~ 5 8 7 8 li 10 11 12 10 ---o_x.;.y_1e_n_m_u1 _ _ _ _ _ 8 8 4 2 1 2 3 4 5 8 7 8 9 10 11 12 DIN µmol/I 30 -25 20 15 10 5 0 ~ - - . - - . - -... --.-....-... - - . - ~ 1 2 3 4 5 8 7 8 li 10 11 12 40 _ _ _ _ _ _ T_ot_-N_..;µ_m_o_1_11 _ _ _ _ 35 30 25 20 15 10 5

0-'--

_{1 2}

---1

_{3 4 5 8 7 8 9 10 11 12} MONTH S1li1mity psu 40 , -35 30 25 20 15 10 ~--.--.--... - . - - . - . - - - . . . . - - l 1 2 3 4 5 fl 7 8 li 10 11 12 Pc:>. µmol/I 1.25 . -1.00 .75 .50 .25 0.00 -+---.--.--... - - . - - -... - . - - - ~ 1 2 3 4 5 IS 7 8 9 10 11 12 Si0₂ µmol/I 30 . . . . -25 20 15 10 Cl•••••••••••••• 5 ···~ ....••.•. ~ 0

+--.-..=~~..--,,---,._::::!::::;::~

1 2 3 4 5 8 7 8 9 10 11 12 2.0 ...,.. _ _ _ _ _ _ T;...;~;...;•t..;;·P_,i;;µ,;;;m;.;;o.;;,U.;;.l _ _ _ 1.5 1.0 .5

...

/\

...• ti.. ··i:r· 1 2 3 4 5 8 7 8 9 10 11 12 MONTH

Figure 3.1.6 Monthly mean values 1993, solid line, compared to the mean annual cycle for the years 1981-1990, dotted line. Stationi P2 in southeastem Skagerrak.

3.2 Kattegat and the Sound

In the surface layer, the temperature followed the mean annual cycle throughout the year.

The salinity however had a peak in the beginning of the year but was lower than mean in

the later part. The spring bloom emptied the pool of nutrients in the surface layer in late

February and early March. During the rest of the year the nutrient concentrations were

clearly below the mean values for the period 1981-1990.

STATION FLADEN SURFACE WATER

Temperarure •c 20 - . - - - , 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 Oxygen mVl 10 8 ·•·a· .a. ... 6 4 2 0 1 2 3 4 5 6 7 8 9 10 11 12 DIN µmol/I 30 - . - - - -- - , 25 20 15 10 5

--··

··•· -0 +-.-~:::::.:~lil'-,c;i-..r;i,,~-'jl"'-jl:...,,--l 1 2 3 4 5 6 7 8 9 10 11 12 40 Tot-N µmol/I 35 30 25 ... O···a. 20 15 ···1>··· 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 MONTH Salinity psu 40 - , - - - , 35 30 25 20 15 10 -+--.---,.--,,--.---,-..,....--,---,---,-.---1 1 2 3 4 5 6 7 8 9 10 11 12 PO, µmoUI 1.25 - , - - - , 1.00 .75 .50 .25 0.00 -i. ... ~~~~;l::::~~-.--.--l 1 2 3 4 5 6 7 8 9 10 11 12 SiO₂ µmol/I 30 - - - , 25 20 15 10 5 0 +-,-....;..:::.ijl:~=q,-;,,--1;1::::::::;~,--r-4 1 2 3 4 5 6 7 8 9 10 11 12 Tot-P moUI 2.0 ...,... _ _ _ _ _..;__,;,.__.;;;..;.;;_;..;..,;. _ _ - - , 1.5 1.0 ••. a. ... Cl ••• '0, a· .5 ·•.l>·••0-' .. 0-··· 0 .o -+--.---.--,,--.--..,....-.--,-...,--,-,---i 1 2 3 4 5 8 7 8 9 10 11 12 MONTH

Figure 3.2.1 Monthly mean values 1993, solid line, compared to the mean annuacycle for the years 1981-1990, dotted line. Station Fladen in northem

Oxygen ml/I 10 - - , - - - . . ; . . ; ; ; . - - - , 8 8

'

2 0 -+---.---.-.--"T"'""-.---r--,,--,r--..--"T"'""-1 30 25 20 15 10 5 0 1 2 3 4 5 8 7 8 9 10 11 12 PO4 µmol/I 1.25 - . - - - . 1.00 .75 .50 .25 0 .00

+ ... --.~~ ....

='F:"4-==i!:::::::;:-....--... --1 1 2 3 4 5 8 7 8 9 10 11 12 SiO₁ µmol/I 8 7 li 9 10 11 12 MONTH

Figure 3.2.2 Monthly mean values 1993, solid line, compared to the mean annua[ cycle for the years 1981-1990, dotted line. Station Anholt E in southem Kattegat.

STATION w LANDSKRONA SURFACE WATER

Temper11ure •c Salinity psu

20 40 15 35 30 10 ₂₅ 5 20 15 0 10 1 2 3

..

5 8 1 8 li 10 11 12 1 2 3

..

5 8 1 8 9 10 11 12

Oxraen ml/1 PO, µmol/I

10 1.25

8 1.00

8

···a-•·••O. •.• a•· .75

4 .50

2 .25

0 0.00

1 2 3 4 5 8 1 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

DIN µmol/I SiOi µmol/I

30 30 25 25 20 20 15 15 10 10 5 5 0 0 1 2 3 4 5 8 1 8 9 10 11 12 1 2 3

..

5 8 1 8 9 10 11 12

40 Tot•N µmol/I 2.0 Tot-P mol/I

35 30 1.5 25 ··•a. .. 20 ····o--·0·•···-0• ... 1.0 15 10 .5 5 0 0.0 1 2 3

..

5 8 1 8 9 10 11 12 1 2 3

..

5 8 1 8 9 10 11 12 MONTH MONTH

Figure 3.2.3 Monthly mean values 1993, solid line, compared to the mean annual

cycle for the years 1981 · I 990, dotted line. Station W Landskrona in the

At Fladen the nutrient concentrations in the deep water were extremely low in March and somewhat lower than normal during the rest of the year. In the southern

Kattegat and the Sound the situation was about the same with the exception for the phosphate content that varied strongly during the year. The concentrations of

total phosphorus and total nitrogen were low in the surface as well as in the deep

water during the whole year.

STATION FLADEN DEEP WATER

20 Tempemturc "C 15 10 5 0 1 2 3 4 5 6 7 6 9 10 11 12 Oxygen ml/I 10 8 8 4 2 0 1 2 3 4 5 8 7 8 9 10 11 12 DIN µmol/I 30 ~ - - - ~ 25 20 15 10 5 0 ---..-..-....--r---r---.---.-.--t 1 2 3 4 5 6 7 8 9 10 11 12 Tot-N µmol/1 40 35 30 25 20 15 10 5 0 1 2 3 4 5 8 7 8 9 10 11 12 MONTH Salinity psu 40 - . - - - , 35 30 25 20 15 • ··••0·•·· .••• 10 -1---,---.--,,--..--.,...""T"""--r---.---r-..--t 1 2 3 4 s 8 7 8 9 10 11 12 PO₄ µmol/1 1.25 1.00 .75 .50 .2S o.oo 1 2 3 4 5 6 7 8 9 10 11 12 SiO₂ µmol/1 30 25 20 15 10 5 0 1 2 3 4 5 6 7 8 9 10 11 12 Tot-P mol/1 2.0 - . - - - , ,.s 1.0 .5 0.0 -+-"""T"--.----r-r--..--r--r---r---r--,...-1 1 2 3 4 5 6 7 8 9 10 11 12 MONTH

STATION ANHOLT E DEEP WATER

Temperature oC Salinily p1u

20 40 35 15 _{··••a-•· ..} 30 10 25 5 20 15 0 10 1 2 3 4 5 8 7 8 li 10 11 12 1 2 3 4 5 8 7 8 li 10 11 12 10 Oxygen ml/I 1 ..25 PO₄ µmol/I 8 _1.00 8

,

... .75 4 _.50 2 ..25 0 0.00 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 li 10 11 12

DIN µmol/I Si02 µmol/I

30 ₃₀ 25 25 20 20 15 15 10 t

_{. - - ~}

... 10 5 ····a ··a-·•0-.. 5 0 0 1 2 3 4 5 8 7 8 li 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

40 Tot-N µmol/I 2.0 Tot-P mol/I

35 .R. 30 1.5 _: .. .-

'

·. _·

.

25 _{... a-·•O-·-a••··d· ·b ...} 20 1.0 15 10 .5 5 0 o.o 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12 MONTH MONTH

Figure 3.2.5 Monthly mean values 1993, solid line, compared to the mean annua! cycle for the years 1981-1990, dotted line. Station Anholt E in southem Kattegat.

STATION W LANDSKRONA DEEP WATER Temperuure •c 20 ...,.. _ _ _ _ _ ....;.. _ _ _ _ _ _ _ __ 15 10 5 0 -+---...--... --.---.-... ---.-...--1 1 2 3 4 5 li 7 8 8 10 11 12 10 _ _ _ _ _ _ o_x.;..y1;:;..c_n_m_v_1 _ _ _ _ 8 8 4 2 1 2 3 4 5 8 7 8 8 10 11 12 DIN µmol/I 30 -25 20 15 10 5 .• - - - ~ .•. o. ... Q. . _.- ~ - · · · a 0

-+---.-...---.---....

1 2 3 4 5 li 7 8 8 10 11 12 40 _ _ _ _ _ _ T_o_t_•N ___ µ_m_o_l_ll _ _ _ _ 35 30 25 20 15 10 5

o-+---.---'

_{1 2 3 4 5 li 7 8 8 10 11 12} MONTH Sali.Dily psu 40 , -35 30 25 20 15 10 -t-....,...--,,--.,...,...,... ________ -"' 1 2 3 4 5 li 7 8 8 10 11 12 PO, µmoVI 1.25 1.00 .75 .50 .25 0.00 I 2 3 4 5 8 7 8 8 10 11 12 S10₁ µmoVI 30 25 20 15 10

\

_/ ··a 5

\/

0 I 2 3 4 5 8 7 8 8 10 11 12 2 _0 -,---=T'-"o..:.t·..:.P_c.m=o.::.VI.;.._ _ _ ~ 1.5 1.0 .$ 0.0 - - - . . . - - - ~ 1 2 3 4 5 li 7 8 8 10 11 12 MONTH

Figure 3.2.6 Monthly mean values 1993, solid line, compared to the mean annual cyclefor the years 1981-1990, dotted line. Station W Landskrona in the

No severe oxygen deficit was mapped during the autumn in the deep water in the

Kattegat area. The lowest concentrations were detected in the southeastern part

during the september expedition, while the oxygen content in the northern part

was about the same during the whole period.

13•

.---.sa·

Bottom Water Oxygen Concentration (ml/I)

4.32 •

Sep.

1993

5.35 • 5.25 • 4.96 • 4.55

i f

3.70

I

.

_{3.21 • 3.07} • 2.79° 2.86 3.19 0 •

Figure 3.2. 7 Oxygen distribution in the bottom water during the September expedition.

57•

3.3 The Baltic Sea

The most dramatic event during 1993 was the large in.flow of high saline water to the

Baltic that occurred in January. The inflow bad effects on the wbole water column in the

Arkona basin, but further into the Baltic only deeper layers were influenced. During the

wbole of 1993 the effects of the inflow could be detected further and furtber into the

central parts. The inflow is described in more details below and the ordinary hydrographic

description will be restricted to the nutrient conditions in the upper layers.

Southern Baltic (Arkona- and Bornholm basins)

In the beginning of March there was a 35-metre deep homogeneous layer in the Arkona

basin. The temperature in this layer was 2.5 °Cand the salinity about 8.5 psu. The spring bloom had not really started and the nutrient concentrations were still high.

During April the temperature in the surface layer had increased to between 3.5

and 5 °C that is higher than normal (normal is the monthly mean for the period

1981-1990). The spring bloom was almost over and in the Arkona basin the

concentrations of nitrate and phosphorus were below detection lirnits (0.10 and

0.02 µmol/I respectively), however, there was still some pbospbate left in the surface

water of

the

Bornholm basin.

It

s

hould also be noted that the content of

silicate

was

rem-arkably lower than normal ca 2.5 µmol/I compared to 8-9.

During the period up to June a strong thermocline at a depth of 15 to 20 m developed,

with surface layer tempera tures around 10 °C. The concentrations of phosphate bad increased

in the Arkona basin while they bad continued to decrease in the Bornholm basin. The

concentrations of nitrogen were dose to the detection limit, while the silicate concentrations

had increased to levels above the normal.

During the summer months the surface temperatures were 1 to 2 degrees below normal,

but since the cooling process during autumn was slower than usual, the temperature was

again normal in October. The concentrations of phosphate and nitrogen remained low

during summer while silicate concentrations were higher than normal, especially in the Arkona basin. Phosphate and nitrogen concentrations rose again during autumn, silica

however, decreased in concentration during the last months of the year instead of rising as

usual. It should be noted that an extremely intense bloom of silica algae occurred in October.

I

STATION BY2 SURPACE WATER Temperature oc Salinity PH 20 10 15 8 ···o•- ...

•

10 4 5 ₂ 0 0 1 2 3 4 5 8 ·7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

OxYaen ml/I P04 µmol/I

10 2.0 8 • • • O • • · ~ .. • .. _1.5 8 1.0 4 ... a-... 2 . s ,•

..

0 0.0 ··o-··· I 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

DIN µmol/I Si02 µmol/I

10 25 8 20 li 15 4 10 2 5 ... .O··· •... .a 0 0 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12 Tot•N µmol/I 30 2.0 Tot-P mol/I 25 ... o. .•. ~ 20 . ..0 .

..,

.... 1.5

15 1.0 _{... o···o.• .. a.. ... o. ...}

10 ···o-•·•0·· .5 5 0 0.0 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12 MONTH MONTH

Figure 3.3.1 Monthly mean values 1993, solid line, compared to the mean annua[ cycle for the years 1981-1990, dotted line. Station BY2 in the Arkona Basin.

STATION BYS SURFACE WATER

Tem peratvre -c Saliøity p111

20 10 15 8

·-o-.

..

8 10 4 5 ₂ 0 0 1 2 3 4 5 8 7

•

li 10 11 12 1 2 3 4 5 8 7 8 li 10 11 12 ml/1 PO4 µmol/l 10 2.0

•

1 .5

•

1 .0 4 2 .5 0 0.0 1 2 3 4 5

•

7 8 li 10 11 12 1 2 3 4 5 8 7 8 li 10 11 12

DIN µmoln SiO2 µmoUI

10 25 8 20

•

15 ... a.···a: _o. 4 10 '1>·-·a··· 2 ... a

.,.

5 0 0 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

30 Tot-N 11,moln 2.0 Tot-P mol/l

25 .. A.

..

_•. 1.5 _.P. • . .• Q.. 20 ... ···· ... 15 o. ... O•••CT ••l>•••••••••C •••• 1.0 10 .5 .. -a. 5 0 0.0 1 2 3 4 5 8 7 8 li 10 11 12 1 2 3 4 5 8 7

•

li 10 11 12 MONTH MONTH

Figure 3.3.2 Monthly mean values 1993, solid line, compared to the mean annual

cyclefor the years 1981-1990, dotted line. Station BY5 in the Bornholm

Considering the deep water, the first expedition was conducted too late to detect the effects

of the inflow in the Arkona basin. In the Bornholm basin, however, a marked increase in

salinity was clear the whole year. The inflow is most clearly reflected in the oxygen

measurements, which gave concentrations well above mean in March. The oxygen

con-tent then decreased during the year and reached normal values in late December. The

concentrations of phosphate and silica were also lower than normal while the nitrogen

concentrations did not seem to be influenced.

STATION BY2 DEEP WATER

Temperature •c 20 ... - - - ~ 15 10 5 0 10 8 8 4 2 0 -2 .4 1 1 2 3 4 2 3 4 5 8 7 B 9 10 11 12 Oxygcn ml/I 5 li 7 8 9 10 11 12 DIN 11mol/l 20 . . . , . . . - - - , 15 10 5 0 -+---,----.---,--,.--~-.----.--.-... ~ 1 2 3 4 5 8 7 B 9 10 11 12 50 ...,... _ _ _ _ T_o_t-_N_.;µ:....m_o_l/1 _ _ _ ~ 40 30 20 10 0 -+---.----.---,-.--...-...-...-~--.--~ 1 2 3 4 5 6 7 8 9 10 11 12 MONTH 20 Salinity psu 15 _{···o·uO. ... a,.,. •• o, .••} ·••o--· 10 5 0 1 2 3 4 5 8 7 8 9 10 11 12 PO₄ µmol/I 8 8 4 2 0 1 2 3 4 5 li 7 8 9 10 11 12 S10₁ 11moUI 125 100 75 50 25 0 1 2 3 4 5 8 7 8 9 10 11 12 8 ...,... _ _ _ _ _ T_o_t-_P__,__m_o_l/1 _ _ ~ 8 4 1 2 3 4 5 8 7 8 9 10 11 12 MONTH

Figure 3.3.3 Monthly mean values 1993, solid line, compared to the mean annual cyclefor the years 1981-1990, dotted line. Station BY2 in the Arkona Basin.

STATION BYS DEEP WATER Temperature °C 20

---=---,

15 10 5 •••• O••·• •••• 0 -1---.---,--...--,--,--,,---,--,----1 1 2 3 4 5 8 7 8 9 10 11 12 Oxygen mVI 10

---..:.-=---

--,

8 8 4 2 ·••C>···<>···o-···°"·•·0. .. _0-•··0····0· •.• 0··•·Q•··· 0 -2 •4 ...,1.... _ _ _ _ _ _ _ ..,...-,.-,,---,--,---1 1 2 3 4 5 8 7 8 9 10 11 12 DIN µmol/I 20 _ _ _ _ _ _ _ _ .:,__ _ _ _ _ _ - , 15 10 5 Q••·· ... o-... .·· a o· ·a·· 0 -1---.---,.-,---,--,--,,---,--,--; 1 2 3 4 5 8 7 8 9 10 11 12 50 Tot-N µmol/I 40

/\

... \. 30

.

.. ._ \ 20 10 0 1 2 3 4 5 8 7 8 9 10 11 12 MONTH Salinity psu 20 - - - . 15 10 5 ··•C>•••C>•••C>··•0-•••0-·•·0-••·0-•••0•··•0••••Q•··· 1 2 3 4 5 6 7 8 9 10 11 12 PO4 µmol/I

s-

---

---,

6 2 0 - 1 - - -- - - . - - , -... -.--.-..-... ~ 1 2 3 4 5 6 7 8 9 10 11 12 SiO₂ µmol/I 125 - - -- - - -- - - - , 100 75 50 25 0 -l---.---,.-,---.--,-- , - - , --,---1 1 2 3 4 5 e 1 a e 10 11 12 Tot-P mol/I 8 _ _ _ _ _ _ ..:...,::.:....:..----'=..:..::.;:__ _ _ - , 6 2 ·••a. ... a. .~·-•O-•-•cr···a. ... o .... 0.····q· ...

~ .

0 -1---.---.--,---,,---,-....,...--,--,--,--; 1 2 3 4 5 & 7 e e 10 11 12 MONTH

Figure 3.3.4 Monthly mean values 1993, solid line, compared to the mean annua!

cyclefor the years 1981-1990, dotted line. Station BY5 in the Bornholm

Central Baltic Proper

The situation in the central Baltic Proper, during March, was very much alike the situation

in the southern part, with the exception that the surface water was homogeneous down to

100 metres. The temperature in the upper layer was significantly higher than mean the

whole year except for the last two months, which were colder than normal. A thermocline

developed during spring and was during summer located at a depth of 15 to 20 m. The

spring bloom started as usual in late March but continued longer than normal. The

concentrations of phosphate and nitrogen did not reach the common low levels until

June-July instead as normal in late May. As in the southern part, the concentration of silicate

was remarkably high during summer, and decreased to levels clearly below mean during

autumn.

In the bottom water at the station BY15 in the Gotland deep, no clear increase in salinity

was detected during the year, however, a rise in the oxygen content was clear during

spring but the effect did decrease during summer. The concentrations of phosphate and

silicate decreased while nitrogen is more difficult to analyse since the redistribution between

STATION BYlS SURPACE WATER

Temperature -c S alloity psu

20 10 15 li ... o .. ·Q:.::8:· .. a: ... 8 10 4 5 ₂ 0 0 1 2 3 4 5 li 7 li 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12 10 ml/1 2.0 PO4 µmol/I ... o-·· 8 1.5 fl 1.0 4 .5 ... <>•··<>•-q 2

'

g ... 0 o.o 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

DIN µmol/I SiO1 µmol/I

10 25 8 20 8 15 .. o .. _ ~ 4 -· . 0-••0-·~~ ... 10 .·· ... h ... 2 \ _{.. .} D••• 5 _·o· 0 0 1 2 3 4 5 fl 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12

30 Tot-N µmol/I 2.0 'Tot•P mol/I 25 20 1.5 15 1.0

.--~---~

10 5 .5 0 0.0 1 2 3 4 5 8 7 8 9 10 11 12 1 2 3 4 5 8 7 8 9 10 11 12 MONTH MONTH

Figure 3.3.5 Monthly mean values 1993, solide line, compared to the mean anual cyclefor the years 1981-1990, dotted line. Statio;n BY15 in the Eastem Gotland basin.

STATION BY15 DEEP WATER 20 ...,. _ _ _ _ T_e_m....;..pe_r_at_u_re_-c _ _ _ _ 15 10

o+-.---...,...~--1 2 3 4 S 8 7 8 li 10 11 12 10 ...,... _ _ _ _ _ o_x.:.,yg:;..e_n_m_tn _ _ _ ---, 8 8 4 2 0 ·2 '"• .. 0.•-cr••• -•1>•••0-ooa,--o-••·•0-•-0-•♦oaoH ◄ -+--.-.---.-... --.-.---...,... ... --.---1 1 2 3 4 5 8 7 8 li 10 11 12 20 DIN µmol/I IS 10 5 0 1 2 3 4 s 8 7 I li 10 11 12 50 To1-N µmol/I 40 ·-a. ..• o•-0-···0· 30 ···a,. ... cr .... cr ·o-20 10 0 1 2 3

..

s I 7 8 li 10 11 12 MONTH 1 2 3 4 S 8 7 8 li 10 11 12 PO, µmol/I

9...,...---8

..

2 ·-o•·•a. ... .,. ... a. ... o-···«>·-o-·-0 +--,,-.----...,... ... --.-... -.-... --.---1 125 100 75 50 25 0 1 2 3 4 5 8 7 8 lil 10 11 12 Si0₂ µmoln .... O••• 1 2 3 4 5 8 7 I 1i1 10 11 12 I ...,...---'T;..;o..;.t•..;.P_:;;.m=o=-UI;:.._ _ _ ~ 8

..

2 0 +--.-.---...,... ... --..-...

--~----1

1 2 3 4 5 8 7 8 li 10 11 12 MONTH

Figure 3.3.6 Monthly mean values 1993, solide line, compared to the mean anual

cyclefor the years 1981-1990, dotted line. Station BY15 in the Eastem Gotland basin.

U/F AR,GOS 93-07-05 - 13

Oxygen concentration less than 2 mlil ~ Area with hydrogen sulphide

.,.

> - - - , ~c

U/F ARGOS 93-10-03 - 09

U/F ARGOS 93-08.()9 -20

Oxygen concentration less !han 2 mlil

@

Area with hydrogen sulphide

Oxygen concentratoon less !han 2 mlil ~ Area with hydrogen sulphlde

3.4 The Gulf of Bothnia

Two visits were made to the area during the year, one in June and one in December. The

situation in the Bothnian Sea surface water (station F26) was normal for the season in June

with the ex.ception for the silicate concentrations that were only half of what is considere,d as normal. In the deep water phospbate, silicate and total-phosphorus all had concentrations

well below mean. In the Bothnian Bay the summer situation was normal in both surface

and deep water. In December all parameters except total-phosphorus show ed concentrations close to normal in both subareas. Total-phosphorus showed values below normal in both deep and siurface water.

STATION F26 SURFACE WATER

Tcmperature "C 20 10 Salini1y psu 15 I -10 I - 4-5 2-0 0 ' _' I ' 2 4 a I 10 12 2 4 e a 10 12 12 Oxygen ml/I 2.0 PO, µmoVI 10 -a- 1.5 a- 1.0 4 -2 - .5 0 _{I I} 0.0 2 4 e I 10 12 2 4 e a 10 12

DIN 1tmol/l Si02 llJDOl/1

10 ₂₅ a 20 -e 15 -4 ₁₀ -2 _s

-r

0 ₀ ' ' I 2 4 _{e e} 10 12 2 4 e I 10 12

Tot-N IWOVI Tot-P mol/I

30 _2.0 25 -20 • 1.5 15 • 1.0 10 • 5 - .5 0 ' I I 0.0 2 4 a a 10 12 2 4 e a 10 12 MONTH MONTH

Figure 3.4.1 Monthly mean values 1993, white bars, compared to the meanfor the years 1981-1990 , dashed. Station F26 in the Bothnian Sea.

STATION F9 SURFACE WATER 20 Tcmpcnoire 'C 10 Salinity p$U 15 8 8 10 4 5 ₂ 0 0 2 4 8 8 10 12 2 4 8 a 10 12

Oxyp ml/I ro. µmol/1

12 2.0 10 -1.5 8-8- 1.0 4-.5 2-0 I I I I 0.0 2 4 8 8 10 12 2 4 8 8 10 12

DIN µ11101/1 Si01 µmol/I

20 !50 15 40 - 30-10 20 -5 ₁₀ -0 0 _I I I I 2 4 8 8 10 12 2 4 8 a 10 12 Tot-N µmoVI 30 2.0 Tot-P Ill 25 -1.5 20 -1!1- 1.0 10 -.5 5-0 I I I I 0.0 2 4 8 8 10 12 2 4 8 8 10 12 MOl'mi MONTH

Figure 3.4.2 Monthly mean values 1993, white bars, compared to the meanfor the

STATION F26 DEEPWATPR T ~ ' C Salloity pill 20 10 111

•-10

"

-s 2-0 0 I I I I 2 4 8

•

10 12 2

_"

8 8 10 12

Oxygen ml/I ro. µm:,1/1

12 2.0 10 -1.!5 8-8- 1.0

"

-

.5 2-0 I I I I 0.0 2

"

8 8 10 12 2 4 8 8 10 12

DIN µm:,1/1 Si01 µmol/I

20 50 15 "0 30 -10 20

-I

5 10 -0 0 _{I I I I} 2 4 8 8 10 12 2 4 8 8 10 12

30 Tot-N µmol/I 2.0 Tot-P 1/1

25-20 - 1.5 15 - 1.0 10 -.5 s-0 _{I I}

'

l 0.0 2

"

8 8 10 12 2 4 8 8 10 12 MONrH MONnt

Figure 3.4.3 Monthly mean values 1993, white bars, compared to the meanfor the

STATION f9 DEEPWATER

Tempenlllre "C Salinity psu

20 10 15 li e 10 4 5 ₂ 0 0 2 4 e 8 10 12 2 4 e li 10 12

Oxygen ml/I P04 µmolJI

12 2.0 10 -1.5 8-li - 1.0 4 -.5 2 -0 I I I I 0.0 2 4 8 8 10 12 2 4 8 8 10 12 DIN 20 µmolJI SiCi JllIIOIII $1 15 40 30 -10 20 -5 ₁₀ -0 0 I I I I 2 4 li 8 10 12 2 4 8 8 10 12

Tot-N µmoVI Tot-P VI

30 2.0 25 -1.5 20 -15 - 1.0 10 -.5 s -0 I I I I 0.0 2 4 8 8 10 12 2 4 8 8 10 12 MONTH MONTII

Figure 3.4.4 Monthly mean values 1993, white bars, compared to the meanfor the years 1981-1990, dashed. Station F9 in the Bothnian Bay.

4.

The major inflow to the Baltic

In

January 1993 there was, for the first time since 1977, a major inflow of saline water to the Baltic. At the turn of the year, a strong high pressure was located east of Sweden, causing the water level in the Baltic to descend below mean. When the high pressure

weakened, low pressure areas began to move into Sweden from west causing strong westerly

winds. This meant that the water leve! rose quickly on the west coast and water with high

salinity from the North Sea and Skagerrak filled the Kattegat area.

The normal strati.fication in Kattegat is characterized by a typical two layer structure, where water with low salinity from the Baltic flows on top of the more saline deep water

originating in the Skagerrak. When a major inflow occurs the first thing that happens is

that the conditions in Kattegat changes so that the stratification weakens while surface

salinity in the southern parts increases. During the period January 6 to 26 about 80 km3 _of

water with high salinity entered the Baltic through the Sound. During the same time about

220 km3 _{entered through the Danish Belts, the salinity of this water was however not that}

high. As a total the volume in the Baltic increased with 300 km3 _{during this period.}

4.1 General hydrographic conditions of the Baltic

The Baltic Sea can be considered as a large fiord with more or less permanent salinity

stratification. A halocline located at a depth of 40 to 100 metres, varying between the

different basins, separates the surface water from the bottom water. The conditions in the

surface water are influenced by fresh water supply and cooling/heating and vary through

the year. The same annual variations do not occur in the deep waters, where the conditions

can be relatively constant for long times, stagnation periods that can last for several years. These stagnation periods can be suddenly broken when new water enters through the Sound or through the Belts or due to waterexchange from one basin to another.

The oceanographic conditions of the Baltic are mainly dictated by the topography, the

water exchange with the Kattegat/Skagerrak and by the fresh water supply. The shallow

sills in the Beits and the Sound hamper the water exchange. At Darss Sill in the southem

Belt Sea the sill depth is 18 metres and at Drogden in the southern part of the Sound only 8 metres. As a comparison, the mean depth of the Baltic is 62 metres.

The water exchange is driven by the difference in water levels between the Baltic and

Kattegat, caused by the weather conditions. The situation changes with the weather and

the current direction is often reversed several times duringa period of a few days. Norrnally

the total exchange during a year is large enough to maintain the stratification in the Baltic but not enough to influence the deep water. Inflows of greater magnitude, which have influence on the deep water takes place irregularly, sometimes with intervals of several years and only under very special weather conditions. Such conditions mainly occur during the winter months, December to February. Even if the sill depth in the Sound is more shallow than the sill at Darss, the Sound is considered as an important passage during an inflow. This is mainly because the distance through the Sound is much shorter than th,e way through the Beits. The mixing processes can only work on a shorter time scale and the salinity of the water passing through the Sound is therefore often higher.

4.2 The stagnation period preceding the inflow

The stagnation period before the inflow 1993 is the longest ever recorded and lasted for 16

years. From 1977 the stratification in the inner deep basins weakened successively and

the salinity in the deep waters decreased. In 1992 the lowest salinity ever, was measured

in the eastem Gotland Basin, 11.1 psu. The oxygen conditions were rapidly becoming bad after the 1977 inflow, and 1982 a redoxcline bad developed at a depth of ca. 125 metres.

The redoxcline was located at the same depth during the whole period even if there was a tendency of deepening the last years because of weekend stratification. The stratification in the Gdansk Basin weekend so much during the stagnation period that it completely broke down due to vertical mix.ing during the winter 91/92. The deep waters were again oxic and would have continued to be so if no new deep water bad entered.

4.3 The inflow

Starting the first week in January and ending the 27th the same month, strong winds were

blowing over the Kattegat and the southern Baltic. The direction of the wind varied but

there was always a westerly component. The water level in southern Kattegat increased 0.5 metres while the water level in the southem Baltic decreased with 0.3 metres. The difference in water levels caused a flow of water through the Belts and the Sound into the Baltic. The 6th of January there was an abrupt increase in salinity in the southern part of the Sound and water with high salinity (>20 psu) flowed across the sill and into the Arcona Basin. At the Darss sill the salinity did not increase until 16-18 January due to the longer way through the Belts.

The inflow caused the water level in the Baltic to rise, and on the 27th of January when the westerly wind ceased the water level bad increased 80 cm. The change in weather, reversed the currents and the main inflow ended.

During the three weeks the inflow lasted about 300 km3 _{entered the Baltic. Out of}

_this

₁₂₅

to 150 km3 _{was high saline water, i.e. having a salinity of more than 20 psu. Approximately}

65 % ofthis water came through the Sound. The total volume of the inflow was comparable to the volume below the sill depth in the Bornholm Basin or half the volum~ of anoxic water in the eastern Goland Basin. The total amount of salt that entered with the in.tlow

was ca 2* 1012 _{kg tbat is 27% of what enters the Baltic duringa normal year.}

Within a week from the beginning of the inflow the Arkona Basin was filled with new water. The bottom water salinity increased from 14 -15 psu up to 20-22 psu, and the oxygen concentrations from 2-4 ml/l up to 6-7 ml/1. A week after the end of the inflow the amount of new high saline water in the Arkona was estimated to be 25 - 35 km3

• Of the

original 120-150 km3 _{about 50 km}3 _{was mixed up into the surface layer and partly}

0 100

-

E

-

_::r: I-0.. 200 UJ Cl 300 400 0 100

E

-

_i!:

200 0.. UJ Cl 300 400 SALINITY NOVEMBER 1992 lsopleth interval 1 psu

OXYGEN NOVEMBER 1992 lsopleth interval 1 ml/I

Shaded area indicates hydrogen sulphide

Figure 4.3.1-4.3.2 Cross-sections of salinity, and oxygen in November 1992, before

0 100

E

-

:I: I-a.. 200 w Cl 300 400 0 100

E

-~ 200 w Cl 300 400 SALINITY JUNE 1993 lsopleth interval 1 psu

OXYGEN JUNE 1993

lsopleth interval 1 ml/I

0 100 E

-:i: 200 I-a.. w Cl 300 400 0 100 ~ 200 a. UJ 0 300 400

SALINITY NOVEMBER 1993

l

sopleth

i

nterval 1 psu

OXYGEN NOVEMBER 1993 lsopleth interval 1 ml/I

Shaded area indicates hydrogen sulphide

Figure 4.3.5-4.3.6 Cross-sections of salinity, and oxygenfrom November 1993,

renewed and a vertical stratification was again developed. At the same time the first signs

of an ongoing renewal of deep water in the eastem Gotland Basin were detected. At the turn of the months May/June the result of the waterexchange was that part of the deep water in the eastem Gotland Basin were free of hydrogen sulphide for the first time for 15

years. In the deeper parts of the basin, in the earlier anoxic water, the oxygen concentrations

rose to 1 ml/1 while the salinity increaseid with 0.8 psu.

The detectable effects of the inflow dec1reased strongly further north. In August, the first

effects were noted as elevated salinity in the Fåro deep. The increase was not more than

0.3 psu and the waterexchange was not strong enough to oxygenize the bottom water,

even if there was a clear reduction of hydrogen sulpbide.

4.4 Long term eff ects

In comparison with other known and documented inflows during the twentieth century,

the inflow 1993 is characterized as a medium sized one, considering both volume and

salinity. Since the inflow was preceded by the longest stagnation period known, the effects

will be limited in the long run. For example, in the eastem Gotland hasin the inflow has

resulted in that the salinity conditions arie similar to the ones that were present 1989, i.e. if

there are no new inflows the effects will disappear in a few years. The effects on oxygen

will disappear even faster, and already in November/December a redoxcline at a depth of

130 metres was developed in the eastern Gotland basin.

It is however known by experience that: inflows often occur in groups, and since the

sali-nity still is rather low in the central Balltic there are good chances that new inflows will

oxygenize the deep water. During the beginning of 1994 increasing salinity and oxygen

concentrations were detected in the eastem Gotland basin. The oxygen concentrations

were as high as 2-3 ml/I in the deep water, the highest for 30 years.

5.

Acknowledgement

We would like to thank the NSEPA for continuous cooperation and the renewal of the

contract witbin the national environmental monitoring program. We would also like to

thank the National Board of Fisheries for a year characterized by improved and deeper

relations. Our special thanks goes to the crew on board the r/v Argos who, as always,

showed good spirit and supplied us wilth professional support around the clock when at

sea. For the help renderd us during winter sampling in the Bothnian Sea we thank the

Appendix: Quality

assurance

The concept of quality assurance

Historically, the quality assurance of chemical, physical and biological measurements

carried out at the SMH! Oceanographical Laboratory has mainly included elements such

as participation in intercomparison exercises, use of well established analytical methods

as well as experienced and skilled personnel. During 1993 we have formalised the concept

of quality assurance rather strictly, building up a quality system for overall control of our

testing activities. A quality system is defined as "organisational structure, routines and

resources aiming to lead and steer the operations concerning their quality". In other words,

a quality system at a monitoring and testing laboratory like the Oceanographical Laboratory

includes all steps taken to make sure that the collected data is of the correct quality and

reliable.

The key components of any quality system are a) to decide what the data will be used for,

and what kind of quality and bow much data this requires b) activities aimed at making the

laboratory capable of producing the required data quality, and c) interlaboratory

comparisons, follow-up activities and traceability to prove that the data is reliable and

correct.

The most visible changes caused by the establishment of the quality system at the

Oceanographical Laboratory have been the appointment of a quality manager, the creation

of a quality handbook, understandable and updated method descriptions, a very formal

keeping of laboratory hooks and the use of control charts for intemal quality control. We

have furthermore initiated a scheme for continuous internal education of all members of

the staff. The latter was considered as extremely important in order to keep the staff

motivated and interested in quality assurance.

A quality manager is a person responsible for implementing the quality system and to

make sure that it is functioning in the intended way. The quality handbook contains arnong

other things, detailed information on bow the laboratory is organised, personal

responsibilities and standard procedures for handling information, planning sampling

activities, checking data etc. The method descriptions describe the analytical methods in

detail regarding preparation, sampling, measurement, calibration and evaluation. Copies

of all descriptions are kept in one dedicated binder that is always kept updated by the

quality manager. This ensures that every person carrying out any testing or measurement

will have access to the latest version of the method description. The staff are encouraged

to always have the method descriptions at hand, no matter how experienced they are within

the field. A formal keeping of laboratory hooks considerably strengthens the traceability

of all activities and, together with the method descriptions, aims at rninimizing the number

of mistakes made in the daily work. Control charts make it possible to subjectively decide

whether a method is under control or not. They are created by analysing a control solution

containing a known amount of the analyte in every batch of samples, and subsequently

plotting the result in a diagram together with the mean value and the control limits (mean

plus and minus two and three standard deviations). An example of a control chart is given

in Figure xx.If the results from the control solution fall outside the acceptable lirnits

control again. Control charts are, together with motivated and experienced staff, the most important element of internal quality control.

Changes in analytical methodologies

In conjunction with the formalising of the method descriptions most physical, chemical

and biological methods used at the laboratory have been investigated in detail and scrutinized for weaknesses. As a result of this many of them have undergone minor technical changes, mainly to increase the confidence in the results obtained through more reliable calibration procedures, the use of control charts and other quality assurance measures.

The manual method for measuring the alkalinity in sea water samples was abandoned

overall in late 1993. Instead a more modem, automated, titration with hydrochloric acid

has been implemented. Extensive intercomparisons between the two methods showed that

the results coming out were identical in accuracy fora range of alkalinity's and salinity's,

and that the repeatability (precision) was better with the new method. An automated titration

of oxygen (Winkler method) has been tested during 1993 but not yet established as the

standard method. Small discrepancies between the old and the new method were found in the intercomparisons carried out; this has to be looked into in more detail before implementing the automated method.

Interlaborative testing comparisons

During 1993 the laboratory has taken part in a number of traditional intercomparison

exercises (intercalibrations), both national and international. As a measure of our own

perf ormance in these exercises we have started to use the z-score, which is calculated as the difference between our res ult and the mean res ult of the group, divided by the standard

deviation of the group. Fora start we have defined a z-score of more than one as a failure.

In other words, as long as our result is less than one standard deviation away from the

mean result of the group the intercomparison will be considered a success. The z-score

cannot be used in exercises with just two or three participants, an unfortunate limitation, but has been a very valuable tool to assess our performance in larger intercomparisons. So

far we have been able to keep the z-score below one in all intercomaparisons and for all

parameters with only the odd exception. If this trend continues we will discuss lowering the z-score limit slightly to put more pressure on ourselves in the future.

Apart from the traditional intercomparisons we have taken part in the interlaboratory exercise

"QUASIMEME", a project funded by the European Union aimed at assuring the quality

of data in European marine monitoring programmes. In contrast to other intercomparisons,

this project has included an ambitious programme for exchange of information between

laboratories, a training scheme for laboratories who do not perform well and workshops

The QUASIMEME intercomparisons have this far included nutrients, heavy metals and

chloroorganics (chlorinated biphenyls, CBs). Since we do not measure heavy metals we

have tak.en part in nutrients and CBs only. The results have been encouraging for us, particularly for the CBs where we have very little experience but nevertheless performed well in the first round. the samples sent out were standard solutions and fish oil. The results for the nutrients, in spik:ed sea water samples at three different concentration levels,

confirmed our status as a skilled and reliable laboratory within that field.

Accreditation

Formal accreditation means that a laboratory has a quality system as required by the

Swe-dish and European standard SS-EN 45001, and that the laboratory thus has the competence

and the resources required to carry out certain measurements. The laboratory still has to

prove, for example by participating in intercomparison exercises or by the use of certified

reference materials, that the data produced actually is correct. Preparations for seeking

accredi tation for the majority of the chemical, physical and biological measurements carried

out at the laboratory are well underway. Most of what was described under the "quality

assurance" section above is also valid for a laboratory seeking accreditation. A formal

application to SWEDAC, the officia! body for accreditation in Sweden, was filed in early

SMHI RO 1 (2)

SMHI rapporter OCEANOGRAFI (RO)

Nr Titel

Lars Gidhagen, Lennart Funkquist and Ray Murthy.

Calculations of horizontal exchange coefficienu. using Eulerian time series current meter data from the Baltic Sea.

Norrkoping 1986. 2 Thomas Thompson.

Ymer-80, satellites, arctic sea ice and weather. Norrkoping 1986.

3 Stig Carlberg et al.

Program for miljokvalitetsovervakning - PMK.

Norrkoping 1986.

4 Jan-Erik Lundqvist och Anders Omstedt.

Isforhållandena i Sveriges sodra och vastra farvatten. Norrkoping I 987.

5 Stig Carlberg, Sven Engstrom, Stig Fonselius, Håkan Palmen, Eva-Gun Thelen, Lotta Fyrberg och Bengt Yhlen.

Program for miljokvalitetsovervakning - PMK. Utsjoprogram under 1986. Gateborg 1987.

6 Jorge C. Valderama.

Results of a five year survey of the distribution of UREA in the Baltic sea. Goteborg 1987.

7 Stig Carlberg, Sven Engsrrom, Stig Fonselius, Håkan Palmen, Eva-Gun Thelen, Lotta Fyrberg, Bengt Yhlen och Danuta Zagradkin.

Program for miljokvalitetsovervakning - PMK. Utsjoprogram under 1987. Goteborg 1988.

8 Bertil Håkansson.

lee re<.;onnaissance and forecasts in Storfjorden, Svalbard. Norrkoping 1988.

9 Stig Carlberg, Sven Engstrom, Stig Fonselius, Håkan Palmen, Eva-Gun Thelen, Lotta Fyrberg, Bengt Yhlen, Danuta Zagradkin, Bo Juhlin och Jan Szaron. Program for miljokvalitetsovervakning - PMK. Utsjoprogram under 1988. Goteborg 1989.

10 L. Fransson, B. Håkansson, A. Omstedt och L. Stehn.

Sea ice properties studied from the icebreaker Tor during BEPERS-88.