Patterns of Recent Sea Level Rise in the East/Japan Sea And Their Ecological implication in the Ulleung Basin

Transcription

1 Patterns of Recent Sea Level Rise in the East/Japan Sea And Their Ecological implication in the Ulleung Basin Sok Kuh Kang 1, Josef Cherniawsky 2, Michael G.G.Foreman 2, Sinje Yoo 1, Hong Sik Min 1, Cheol-Ho Kim 1 and Hyoun-Woo Kang 1 Korean Ocean Research & Development Institute, Ansan, Seoul, Korea 1 Institute of ocean Sciences, Sidney, B.C., Canada 2 Science Board Symposium, PICES XIV October 3, 25 Vladivostok, Russia

2 Content of Presentation 1. Research Background -Issues of global sea level rise (GSLR) -SLR study background in the EJS 2. Data Analysis 3. Results -General SLR features from coastal tide, T/P and thermosteric sea level (TSL) -Long-term (decadal) trend -Eddy contribution to large SLR rate -Deep water warming effect to SLR 4. Ecological aspect in relation to eddy activity in UB 5. Summary and conclusion

3 1.Research Background Warming of the World Ocean (Levitus et al., 2 and 25) Yearly heat content anomaly in the upper 3m 197 Peak:1998 Heat content (1955 to 1998) Increase by J (-3m) -Mean temperature increase :.37 -Global mean temp. increase from to 3m :.171 -Warming rate :.2W m -2 The Pacific Ocean has been warming since 195s substantial change : to 3m in each ocean (the North Atlantic in depth greater than 1m) PDO-like signal

4 1.Research Background The rate of Gobal Sea Level Rise(GSLR) and its cause ( Enigma ) 1. What is the rate of 2 th Century GSLR?.5-.7mm/yr or mm/yr? 2. What is the causes of GSLR? Thermal expansion? Freshwater exports from continents?

5 1.Research Background Cabanes et al.(21, Science) Global mean sea level( ) Pseudo global mean thermosteric 1.4mm/yr PSMSL records at 25 tide gauges:1.6mm/yr Global mean thermosteric.5 mm/yr PSMSL GSLR seems to be overestimated!!! Miller and Douglass (24) argued this

6 1.Research Background Miller and Douglas (24) Pacific region; SF,SD,HO,BB -Volume change accounts for only a fraction of SLR -1.5~2.mm/yr for GSLR -Mass change play a dominant role ~2mm/yr.5mm/yr

7 1.Research Background Antonov et al.(22, JGR) Spatially averaged(5 S-65 N)5-year running mean.5mm/yr.5mm/yr -A decrease in global mean salinity has occurred -This increase of freshwater causes SLR at rate of 1.3±.5mm/yr

8 1.Research Background Munk (23, Science) δh eustatic = ( ρ / ρ) δh steric = 36. 7δh steric =1.8mm/yr, Ocean area=3.6 1**8km² If SLR by salinity change is known, SLR due to mass input can be calculated Eustatic rise due to mass input corresponds to 515km³/year or 1.4mm/year 2th-century SL remains an enigma We don t know warming or melting was dominant

9 1.Research Background Warming of the EJS region -Report of sea water warming Minami et al.(1999): long-term increase of temp. below 8m and 5m Kim et al.(21):.1-.5 C warming in the upper 1m layer over the last 4 years Present study background Present study backround Interest in examining what the rate of SLR is in marginal sea such as EJS and what the cause of SLR is? If it is due to warming, is it due to deep or upper water warming? Ecological aspects (later)

10 Example of Warming Evidence in the East/Japan Sea (EJS) Station coverage over 3 years (1941 to 1969(1973)) 48 o 48 o 48 o o 46 o 46 o 44 o 44 o 44 o 42 o 42 o 42 o 4 o 4 o 4 o 38 o 38 o 38 o 36 o 36 o 36 o 34 o 128 o 13 o 132 o 134 o 136 o 138 o 14 o 142 o 34 o o 128 o 13 o 132 o 134 o 136 o 138 o 14 o 142 o 128 o 13 o 132 o 134 o 136 o 138 o 14 o 142 o Temperature Increase Trend over 3 years (3~7m) Temperature ( o C) Depth (m)

11 2.Data Analysis Data -Tidal record : 2-3 yrs -Topex/Poseidon data (9yrs) : '93-'1 -Hydrography data: Period : '6 - ' 1 or '93-'1 Source : KODC & JODC (JODC :.2 x.2 or.4 x.4 ) -Air Temp. data

12 2.Data Analysis Analysis -Tidal record : anomalies for 13 tidal stations -Topex/Poseidon(T/P) data : mean slope for non-tidal residual -Temperture data : calculate sea level rise by salinity and temp. change -Air Temp. data : anomalies Comparison of thermosteric sea level and T/P

13 Yearly Mean Sea level : tidal data 14 Y = * X SAKAI Tide (cm) Y = * X Southern J coast Y = * X SAIGO MAIZURU Y = * X Y = * X 1 Y = * X Y = * X HAMADA Y = * X Y = * X WAKKANAI Y = * X 16 Y = * X FUKAURA Y = * X Tide (cm) Northern J coast Y = * X Y = * X TOYAMA AWA SHIMA Y = * X Y = * X

14 3.Results : SLR from tidal data Air temperature anomaly( o C) 2 1 a Air temp anomaly Slope:.14.4 C/yr Recent 9-year( 93-1) increasing rate (Tide gauge) K. side: 7.7mm/yr J. side: 6.3mm/yr Average : 6.5±.7mm/yr Anomaly of mean sea level (cm) b Sea level anomaly Slope:2.9.7 mm/yr Slope:6.5.7 mm/yr

15 3.Results : TSL and T/P comparison Comparison of TSL with T/P at three points Various Sea Levels Steric sea level (SSL) : MSL variation by density (T, S) variation T/P track Thermosteric sea level (TSL) : MSL variation by temp. variation Harosteric sea level (TSL) : MSL variation by sal. variation X2 X3 Eustatic sea level (ESL) : MSL variation of added mass by ice melting in the continents X1

16 Comparison of TSL with T/P at 3 crossover points SSL TSL Southwestern EJS(X1) Integration down to 3m Smoothed T/P Ulleung basin(x2) Western Yamoto basin(x3) Thermosteric sea level explains most of the observed SLR pattern in the EJS

17 Results : SLR rate from TSL & T/P for 9 years -Generally increasing trend with inhomogeneity -SLR rate from T/P analysis for the whole EJS : 5.4±.1 mm/yr SLR rate at southern region -T/P at S. EJS: 6.6±.4mm/yr -Tide data : 6.5±3.3 mm/yr -TSL analysis: 5.7±2.4 mm/yr Thermal expansion may play a dominant role in EJS SLR at least during recent 9 years

18 SLR relation between EJS and World Ocean? Cabanes et al.(21) Recent 6yr global SLR EJS pattern reflects feature in the northwestern Pacific (T/P) Recent 41yr global SLR (TSL) ~.5mm/yr Steric SLR

19 3. Results (focusing topics) -Long-term (decadal) trend of TSL -Inhomogeneous SLR : Eddy contribution to locally large SLR rate? -Deep water warming effect to SLR

20 3. Results : Long-term (decadal) variability of TSL 4 2 Ulleung basin (P4) Y = * X a' = -.43 mm/yr Y = * X a' = 11.8 mm/yr -Long term variability Data : PDO-like(?) signal : ~15yr oscillation Same pattern in heat content anomaly of Pacific Ocean j16.3 Yamato basin (P5) Y = * X a' =.4 mm/yr Y = * X a' = 2.77 mm/yr -Recent sea level trend : in increasing phase from Heat anomaly Levitus Fig

21 3. Results :4 points Smoothed TSL P4 Smoothed TA

22 The cause of inhomogeneity? (UB & YB.vs. YR & SE) YR Temp. anom. examined in box regions 6 hydrography stations inside UB UB YB SE

23 Cause of inhomogeneity : TSL and Temperature anomaly TSL 3 TSL (cm) Ulleung and Yamato basins 1 a Yamato Rise and SE region 4 Slope : 25.4 mm/yr b 2 2m b 1m c 2m yr. -1 d 5m 5 Temp. anomaly (8C) 3m c Temp. anomaly (8C) yr. -1 TA yr. Temp. anomaly (8C) Temp. anomaly (8C) Temp. anomaly (8C) 196 Slope : 1.9 mm/yr -2 Slope : 13.3 mm/yr -3 1 d 3m e 5m Large TA variability by eddy existence Temp. anomaly (8C) Mild TA variability Temp. anomaly (8C) TSL (cm) 2-2 TA Slope : 7.9 mm/yr a

24 Large temp. anomaly with/without eddy at depths '99 YB Then, TA by eddy can give an affect on SLR trend? Depth (m) '97 UB without eddy '93 UB with eddy '92 YB Temperature ( o C)

25 3. Results TSL TSL (cm) a Time-varying eddy contribution to TSL trend Slope : 25.4 mm/yr Slope : 13.3 mm/yr Profile with absence of an eddy TA TA Temp. anomaly (8C) Temp. anomaly (8C) b 2m c d 14 yr. 17 yr. 3m 5m Ulleung basin case If eddies exist longer period, mean of TA may increase Temp. anomaly (8C) Depth (m) UB box Profile with presence of an eddy Temperature ( o C)

26 3. Results : Sea Level Rise Effect by deep water warming TSL increasing rate -Integration from 8 to 2(25)m -~About.1mm/yr in both basins Depth (m) PotentialTemperature(C) PotentialTemperature(C) Ulleung basin Depth (m) Yamato basin

27 3. Results : Biological implication in relation to eddy activity in the Ulleung Basin -Eddy intensity seems to be reinforced or intensified over some period -If eddies shows such a trend over limited time period, can there be biological relation in the Ulleung Basin? Heat content(1 22 J) Layer: -3 m(yearly) -7 m(yearly) -3 m(pentadal) Heat content Pacific Depth (m) 1 2 Profile with absence of an eddy Profile with presence of an eddy Year Temperature ( o C)

28 Annual cycles in phytoplankton abundance in the UB In the UB, seasonal change in the mixed layer depth drives the annual chlorophyll patterns which exhibit bimodal increases (spring and autumn blooms). After spring blooms, the surface chlorophyll-a in summers decreases down to annual minimum due to nutrient limitation among other things (nitrate values are typically less than.3~.5 µm in August). Light limitation Nutrient limitation

29 Hypothesis If eddies become frequent and strong, they could possibly transport nutrients into upper mixed layer in summer. If that is the case, eddy activity would increase surface chlorophyll-a in summer. The effects of eddies would be most evident when nutrient limitation is strongest, probably in August.

30 Comparison of Chl-a in August UB (Ulleung Basin): 13.5~131.5E, 36.5~37.5N YB (Yamato Basin): 135~136E, 38~39N 12x12 pixels (9km)

31 SeaWiFS Chl-a in August.45.4 Strong eddy activity SeaWiFS Chl-a (mg m -3 ) *Error bars: SE Year Ulleung Basin Yamato Basin

32 Possible mechanisms of nutrient transport Entrainment of coastal upwelling water Isopycnal transport?(yentsch and Finney,1985) YB UB

33 Summary & Conclusion : Recent 9 yr( ) SLR feature in East/Japan Sea(EJS) - Larger increasing rate than global average( ) 98) - T/P result well compared with TSL Mechanism of sea level rising in the EJS - Driven mainly by upper layer warming effect (later( in phase with global trend) - Subject to decadal pattern (PDO?) of Pacific heat anomaly - Deep water warming effect being minor until now Large SLR pattern in Ulleung & Yamato basins - Affected by large decadal pattern influenced by Pacific signal Recent 9-year 9 trend : increasing phase after initial decrease - Dominated by eddy intensity (size and duration) Ecological implification - Reinforced eddy activity increases the surface chlorophyll-a in summer in the Ulleung Basin

34 Thank you!