Long-term Variability of Cold Waters and Their Movements in the East Sea

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(1)Long-term Variability of Cold Waters and Their Movements in the East Sea Kyung-Il Chang1, Hanna Na1, Kwang-Yul Kim1 Yun-Bae Kim2, Kuh Kim2 Jae-Hak Lee3 1Seoul 2 Pohang 3Korea. National University. University of Science and Technology. Ocean Research & Development Institute. 해양생태계와 기후변화 Workshop, 국립수산과학원, 2010. 4. 22-23. 1.

(2) Measured Deep Currents at EC1 (‘97~’08). 2.

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(4) FOURTEEN-YEAR LONG MOORED CURRENT MEASUREMENTS Contributors: Sang-Kyung Byun (KORDI), Nelson Hogg, Scott Worrilow (WHOI), Sang-Chul Hwang (KORDI), Randolph Watts (URI), William Teague (NRL), Jae-Chul Lee (KIOS), Yang-Ki Cho (CNU). Not the least, also crews of R/Vs Eardo, Tamyang, Haeyang2000 and many others………… Currently supported by MLTM (CREAMS/PICES EAST-I Program) Mean currents and variability on multiple timescales in the Ulleung Interplain Gap of the southwestern East Sea: Review and new findings Yun-Bae Kim, Kyung-Il Chang, Sang-Shin Byun, and Jae-Hak Lee Relationship between the interannual variability of the Korea Strait Bottom Cold Water, upper water temperatures and atmospheric forcing in the East/Japan Sea Hanna Na, Kwang-Yul Kim, Kyung-Il Chang, Kuh Kim, and Shoshiro Minobe 4.

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(6) A Miniature Ocean (East Sea MOC). Courtesy, Dong-Jin Kang (KORDI) Courtesy, JongJin Park (WHOI). 6.

(7) Upper & Deep Circulation. Upper and abyssal circulation, adapted and modified from (Senjyu, 1999; Senjyu et al., 2005). 7.

(8) Today’s topic Cold (<1°C) Water in the East Sea (>90% of total volume) 1. East Sea Deep & Bottom Water (<0.1°C) 2. Korea Strait Bottom Cold Water (<10°C) µ North Korean Cold Water Same source region (Japan Basin) Different depth layers of their occurrence Can be called a shallow limb & deep limb of the ‘East Sea MOC’ 0. 19. 23. 20. 17. 11. 21. Depth (m). 40 7 5 9. 17. 60 80. 25. 17. 9 7 5. 100. 19. 15 13 9 11 57 15. 13 15. 11. 120 9 7 5 11 9. 140 160. 10. 21. 35. 46. 7 56. 71. Distance (km). 85. 98. 112. 5. 8.

(9) After 24°N excitement by Bryden et al. (2005).

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(11) From a selection of the new IPCC simulations „best estimate“ -25% until 2100 (-4±3Sv) but no decrease until now! (courtesy M. Latif). „best estimate“. 11. http://ioc-goos-oopc.org/meetings/oopc-11/presentations/OOPC11-3.3-Schott-MOC_web.pdf.

(12) Water Mass Changes Kang et al. (2003). Whether these water mass changes are accompanied by comparable changes in the deep circulation ?.

(13) (Key) Questions ? [Deep limb of the EMOC] 1. Does the upwelling of deep waters occur in the East Sea like the global conveyor belt ? If so, where do deep waters upwell ? 2. Is slowdown of EMOC happening ? 3. If so, what are the implications ? 4. What makes the regional difference of warming of deep waters ? [Shallow limb of the EMOC] 1. Can we draw schematic picture for this ? 2. What are the long-term signals and their causes ? 3. Any connectivity between the shallow & deep components ?. 13.

(14) Mean Abyssal Currents Kim et al. (2008); Chang et al. (2010). Hogan et al. (2000). 14.

(15) Deep Current Measurement in UIG (‘02~’04). Record-length mean currents. 15.

(16) Time-series of Deep Water Transport in UIG Chang et al. (2009). Negligible net transport: implication à no significant upwelling Dominant intraseasonal variability on timescale of 20-50 days Mean inflow transport: ~0.15 Sv 16 Transport at EC1: 53% of the inflow transport.

(17) Inflow transport in UIG (Tr). An Index for Deep Water Transport in UIG. r = 0.8 Tr (Sv) = 0.078 ´ V (cm/s) – 0.069. EC1 velocity (V) 17.

(18) Mean Transport Balance in UIG. 0.3 Sv 0.15 Sv 0.15 Sv. 0.15 Sv. 0.15 Sv. 18.

(19) Time-series of Transport & Velocity. Velocities. Transport. Mean transport: 0.162 Sv (>0.15 Sv between 2002-2004) Annual & interannual variation (~0.1 Sv; summer max.; 3-4 years) Linear trend: decline of 0.022 Sv per decade (14% per decade). 19.

(20) A reconstruction of the Atlantic MOC derived from the ECMWF operational reanalysis exhibits the large seasonal (1.8 Sv) and interannual (1.9 Sv) variability at 26N with a small decrease of 0.07±0.01 Sv, equivalent to a reduction of 4% per decade, over the 48-year period between 1959 and 2006. 20.

(21) OAFlux ERA40. -150. 2. Heat Flux (W/m ). -100. Net surface heat flux off Vladivostok in winter ~1.5-year lag (?). -200 -250 -300 -350. 1970. 1975. 1980. 1985 1990 Time (Year). 1995. 2000. 2005. But an increasing trend of surface heat loss since mid-1990.. 21.

(22) Warming of Deep Water near bottom. Depth. Long-term trend near bottom (Temperature accuary,0.001oC). WJB. 0.0015 ± 0.0001 oC/year (0.15 oC/100 year). EC1. 0.0017 ± 0.0002 oC/year (0.17 oC/100 year). UB. 0.0021 ± 0.0001 oC/year (0.21 oC/100 year). Why the warming rate is the highest in the Ulleung Basin ? 22.

(23) Interannual variability of the Korea Strait Bottom Cold Water Vertical temperature section in the Korea Strait. Data. Period (year). Upper water temperature of the East Sea. 1962-1996. 10m wind (ECMWF ERA-40). 1962-2001. Surface wind (NCEP/NCAR reanalysis). 1962-2008. KODC hydrography station 2-9. 1968-1998. KODC hydrography station 2-4. 1968-2008.

(24) CSEOF (Cyclostationary EOF) analysis T (r , t ) = å Bn (r , t ) Pn (t ) Bn(r,t): physical process (e.g. El Niňo, seasonal cycle) Pn(t): PC time sereis (amplitude) Bn(r,t)=Bn(r,t+d); covariance statistics is periodic d: nested period. Vertical temperature section (red solid line) 12 months for 35 years: 420 months Each B(r,t): 12 months Each P(t): 420 months.

(25) Vertical T section, CSEOF mode 1. Annual Cycle.

(26) Vertical T section, CSEOF mode 2. Interannual KSBCW variability. spectral peak: ~3 years also a linear trend.

(27) Temperature anomalies regressed on the interannual KSBCW variations.

(28) Mean temperature and regressed temperature anomalies on the interannual KSBCW variations. 40N 37N.

(29) 10 m wind stress and the wind stress curl anomalies regressed on the interannual KSBCW variations. downward Ekman pumping along the east coast of Korea.

(30) Extended PC time series of the interannual KSBCW variability ECMWF wind. NCEP wind. KODC. Correlation coefficient. ECMWF Wind. NCEP Wind. KODC station 2-4. ECMWF Wind. -. 0.88±0.02. 0.56±0.07. NCEP Wind. 0.88±0.02. -. 0.48±0.07. KODC station 2-4. 0.56±0.07. 0.48±0.07. -.

(31) Summary • •. • • • • • •. An index of the deep water transport, Tr (Sv) = 0.078 ´ V (cm/s) – 0.069 A reconstruction of the transport time series exhibits the large seasonal (0.1 Sv, summer max.) and interannual (0.1 Sv, period of ~ 3-4 years) variability with a linear declining of -0.022±0.002 Sv per decade, equivalent to a reduction of 15%, over the 11-year period between 1996 and 2008, about 4 times larger than a recent estimate of the AMOC declining of 4% per decade. The declining of the southward transport is accompanied with the warming of deep water, 0.015°C per decade equivalent to an increase of 20%. Wintertime heat loss appears to be related with the interannual variation with a time lag of about 1.5 years, but it shows an increase trend since mid-1990. Interannual KSBCW variability of ~ 3-year periodicity Relationship with the upper water temperature variability Relationship with the southward wind stress along the east coast of Korea Reasonable interannual covariability between the KSBCW and the basin-scale wind stress..

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(33) OAFlux ERA40. -150. 2. Heat Flux (W/m ). -100. -200 -250 -300 -350. 1970. 1975. 1980. 1985 1990 Time (Year). 1995. 2000. 2005. 33.

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