Some evidence about climate changes and shifts in the

Tarmo Soomere

Centre for Nonlinear Studies Institute of Cybernetics at University of Technology

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Outline

a The Baltic Sea a Motivation a The water body ¾ Stability of circulation a Surface effects ¾ Water level ¾ Waves ¾ Ice a Response

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Baltic Sea: a strange water body

Inner sea of the EC Relatively shallow: S=380,000km2, V=21,000km3, mean depth ~55m Long coastline, no tides, no jet currents Combines properties of (i) large estuary, (ii) large lake, (iii) small ocean Water exchange time ~25 years Brackish water, with strong horizontal & vertical gradients, small circulation cells Particularly sensitive sea area by IMO SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Motivation: drastic changes in many sea state parameters Secchi depth 1900 – 2000 in the Baltic Sea

Bay of Sea of Bothnia Bothnia 7Æ5m 10Æ5m

Gotland Bornholm Sea, North Basin 10Æ4m 8Æ5m

Courtesy to MattiSEAMOCS Leppäranta, workshop University ofPalmse 11-12 October 2007 Baltic Sea: climate shifts and changes The sea-surface temperature has increased in 50 (salinity decreases) years by about 0.5 degrees (SST increases)

Fig xx. Annual averages of surface water 0-30 m) (a) salinity and (b) temperature at Utö , Tvärminne and in the years 1950- 1999. Seasonal averages of temperature (May-July („), August-November (O), and December-April (S)) are shown in (b)

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Variability versus long term changes: Baltic Sea as a test area arelatively small size: susceptibility with respect to the external forcing factors amostly separated from the rest of the World Ocean aforcing factors easy to identify & measure abasin-wide studies within a reasonable budget anumerous changes of the forcing conditions and of the reaction of the water masses already identified during the latter decade

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Part I

The water body

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Classical circulation pattern: estuarine transport combined with front development

Two water different water River Kymi masses Æ Helsinki front

line s sa River Neva Les e alin Three re s Mo River Narva Narrow inflow large along the rivers southern coastSEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Estuarine transport: may be reversed the entrance to the Gulf may serve as a “chimney” for ventilation of deep water of the Baltic Sea

Fig. Xx. Time series in the western part of the Gulf of during 1998: (a) salinity observations at station F3 on the levels from 10 to 70 m, (b) deep-layer volume transport calculated from the wind measurements at Utö island (7-days moving average) (c) the wind seep at Utö (original data, thin line, 7-days moving average (thick line).(Elken, Raudsepp, Lips, 2003) SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Conveyor belt: does it exist? Is it stable?

“chimney”

Elken et al. 2006, Elken and Matthäus 2007 SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Rossby radius – “measure” of size of structures in the water body

9Affects (the size of) mesoscale features Æ transport properties, water age pattern etc. etc.

Average baroclinic Rossby radiusSEAMOCS in the Gulf workshopof Finland based on nearly 2000 CTD-cast in 1990’s (Alenius,Myrberg, Nekrasov, 2003). Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Patterns: clear structure in the subsurface layer (average 1987-1992)

Transport out of the gulf

More or less persistent circulation cells

Coastal inflow current Gradual drift of current cells to WSW

The simulated mean circulation in the subsurface layer between 2.5 and 7.5 m from 31 August 1987 to 31 August 31 1992. OLEG ANDREJEV, KAI MYRBERG & PETER A. LUNDBERG. Age and renewal time of water masses in a semi-enclosed basin SEAMOCS workshop application to thePalmse Gulf 11-12of Finland. October -2007 Tellus A 56Baltic (5), Sea: 548-558, climate shifts2004. and changes Climate change: does it involve change of current patterns? (just because of change of the Rossby radius?)

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes ... Or the water age (~measure of water quality, pollution level etc.)

Fig. Xx. Horizontal distribution of water age in the near-surface layer (in days) between 2.5 and 7.5 metres on August 31, 1992 after a 5-years simulation (Andrejev, Myrberg, Lundberg, 2004).

The oldest bottom water -- about 8.3 years Water renewal time – 5 years (river discharge only: 10 years)

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Part II

Forcing factors and reaction of sea surface Wind structure Surface waves Water level Sea ice SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Wind data: from NE Baltic Sea

Helsinki Inkoo Kataja Isosaari Hanko Kalbådagrund Utö

Naissaar

Ristna Tallinn Kunda Pakri Harku Ülemiste Vilsandi

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes 20 Distribution of wind directions at Vilsandi 1969-1975 Wind rose: 15 changes 10 shape

5

0 0 50 100 150 200 250 300 350

Vilsandi, 20 1977-1991 Once each 3 15 hours

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0 0 50 SEAMOCS100 150 workshop200 250 300 350 Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes 20 No changes in the 1977-1991 1980s and the 15 1990s

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0 0 50 100 150 200 250 300 350

20 1992-1999

15

10

5

SEAMOCS workshop 0 0 50 Palmse100 11-12150 October200 2007250 300 Baltic350 Sea: climate shifts and changes Response I: upwelling patterns strongly wind-structure-dependent

Upwelling & Fig xx. A 10-years mean description of upwelling index for the Gulf vertical mixing: still of Finland (Myrberg and Andrejev 2003). a challenge for circulation models SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Response II: coastal processes

Pirita Beach near Tallinn: usually a nice beach SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes After a storm from a “wrong” direction

Photo: Kaarel Orviku SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes After another storm from a “wrong” direction

SEAMOCS workshop Photo: Kaarel OrvikuPalmse 11-12 October 2007 Baltic Sea: climate shifts and changes ... While storms from “correct” direction cause “reasonable” damage

SEAMOCS workshop Photo I.Kask Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Possible background: Also in the Baltic Proper strongest winds come from unexpected Dominating south North winds: also directions and southwest present winds8

Hanko 6

Muuga 4

2 Blue: all winds Green: winds >5 m/s 0 Red: winds >10 m/s N NE E SE S SW W NW N West and east winds blowing along the gulf axis SEAMOCS workshop Palmse 11-12 October 2007 (specificBaltic Sea:to theclimat eGulf shifts andof changesFinland) Sea level at Hanko: change of uplift rate?

Hanko

Data: Finnish Institute SEAMOCS workshop of Marine ResearchPalmse 11-12 October 2007 Baltic Sea: climate shifts and changes Turku (130 cm) Helsinki (151 cm) Hamina (197 cm) Hanko (132)

148 197 146 150 152 134 135 139 160 194 148 157 155 202 207 170 Ever highest in the history: 160 275 St Petersburg +421 (1824), 150 253 this night: +230

SeaSuursaar level: et al., Boreal unexpected Environment Research maxima 2006 SEAMOCS workshop (red: newPalmse maxima 11-12 October 2007 in JanuaryBaltic Sea: climat 2005)e shifts and changes Long-term wave statistics in the northern part of the Baltic Sea

At a few locations aBothnian sea: aOpen sea: 1996Æ (Kahma et al. 2003) aAlmagrundet 1978-2003 (Broman et al. 2006) aGulf of Finland 1991Æ ice-free time (Pettersson 2001 & 2004)

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Long term trend: wave heights seem to increase by 1.8%/year (Almagrundet) 1.5 WHM 1993-2003

SimRad 1978-1995

1 100

0.5 North Atlantic: 50 increase by ~1% (doubtful data)

(Gulev & Co) % rate, success Measurement Average significant wave height, m height, wave significant Average

0 0 1980 SEAMOCS1985 workshop 1990 1995 2000 Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Years 1.5 Long-term variation of annual mean 1 100 wave heights: Two Almagrundet 0.5 50 SimRad data:

WHM data: % rate, success Measurement data sets fit perfectly m height, wave significant Average just the 0 maybe just0 1980increasing1985 1990 1995 2000 Annual mean observed wave height at Vilsandi 1954-2005Years they are 1.2 phase of correct?Baltic Proper long-term 2 × 7.4m 1

V ery strovariability? ng sto rm , no t reco rded 7.7m 0.8 Almagrundet Hs=7.8m 7.2m

0.6

0.4 Annual mean wave height, m

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0 SEAMOCS workshop 1955 1960 Palmse1965 11-121970 October1975 2007 1980 Baltic1985 Sea: climat1990e shifts and1995 changes2000 2005 Soomere & Zaitseva, Proc. Estonian AcademyYear Sci. 2007 Annual mean observed wave height at Vilsandi 1954-2005 1.2 Baltic Proper

2×7.4m Trend1 since 1997: opposite to Very strong storm, not recorded wind speed trend 7.7m 0.8 Almagrundet Hs=7.8m 7.2m

0.6

0.4 Annual mean wave height, m height, wave mean Annual

0.2 SimRad

Observed wave Observed wave 0 1978-1995 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005

height, annual mean height, annual Year (doubtf ul data

SEAMOCS workshop ?) Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Scatter diagram of wave heights and periods One storm January 1984 7 Wave 6 heights and 5 periods: reasonable 4 3 Swell- Wave height, m Isolines for 1, 3, dominated 10, 33, 100, 330, 2 seas 1000 and 3300 1 cases, 1978-1995 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 SEAMOCS workshop Wave period, s Broman et al. (2006)Palmse 11-12 Oceanologia October 2007 48 Baltic(S) Sea: climate shifts and changes Unexpectedly high: 09 Jan 2005

Measured 7.2 m; model 8.5 m

Model >11m; Factual Hs ~9.5m

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes This sea surface around is not always in motion

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Ice climatology (Svetlana Jevrejeva, Matti Leppäranta) ¾ large east – west variability: one month in both freezing date and break-up date in the alone ¾ ice break-up has become earlier by 10 days/100 years (Utö) ¾ probability of freezing decreasing 20% units per 100 years

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Change in ice conditions: drastic Sooäär and Jaagus 2007

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes (some) lessons to learn a extremes becoming more extreme a the factual (extent of) response poorly understood a trends of the average and of extreme values of certain properties are different! a and even trends of the forcing factor and the response are different (wind // waves)

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes Wishing further challenges and success to everybody!

SEAMOCS workshop Palmse 11-12 October 2007 Baltic Sea: climate shifts and changes