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March 17, 2006, 17:10-17:30 2 nd Argo Science Workshop Venice Convention Center

Seasonal and interannual variability of temperature inversions in the subarctic North Pacific*. March 17, 2006, 17:10-17:30 2 nd Argo Science Workshop Venice Convention Center. Hiromichi Ueno 1 , E. Oka 1 , T. Suga 1,2 & H. Onishi 3 1:Argo JAMSTEC 2:Tohoku Univ. 3:Hokkaido Univ.

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March 17, 2006, 17:10-17:30 2 nd Argo Science Workshop Venice Convention Center

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  1. Seasonal and interannual variability of temperature inversions in the subarctic North Pacific* March 17, 2006, 17:10-17:302nd Argo Science Workshop Venice Convention Center Hiromichi Ueno1, E. Oka1, T. Suga1,2 & H. Onishi3 1:Argo JAMSTEC 2:Tohoku Univ. 3:Hokkaido Univ. *GRL 2005 (2005GL023948)

  2. Introduction1 (2/20) What’s T-inversion?

  3. Introduction2 (3/20) Horizontal distribution Freq. of ∆T > 0.5C (%) WOD01 & Argo Annual Ueno & Yasuda JPO 2005 T-invesions: North of 40N, low: ~50N east of 180º, along Aleutian Islands

  4. Introduction3 (4/20) Formation of T-inversions (1/2) Uda 1963, Roden 1964 T-min <= Seasonal cycle of surface cooling & heating with surplus precipitation Cooling Heating T-min:preserve the memory of wintertime atmospheric conditions. T-min T-max => affect the SST in the next winter via re-emergence of T-min water (Wirts & Johnson 2005)

  5. Introduction4 (5/20) Formation of T-inversions (2/2) Ueno&Yasuda 2000,2003, Endo et al. 2004 Heat and salt of T-max <= Warm and saline water transport from the K-O MWR east of Japan Ueno & Yasuda JGR 2000 T-max: related to water-mass exchange between subtropical and subarctic gyres.

  6. Introduction5 (6/20) T-inversion as a heat reservoir Mignot et al. 2006 Potentially T-inversion just below winter ML: Heat reservoir Its erosion or upwelling => positive SSTA => influence on climate Subarctic NP (136W, 48N) Mignot et al 2006 submitted to JGR

  7. Introduction6 (7/20) Previous studies Tmax Depth WOA94, Annual Ueno&Yasuda2000 T-inversions in the subarctic NP have been examined mostly using historical hydrographic data, that are quite limited in winter. =>The formation and seasonal evolution of T-inversions are not fully understood, and their interannual variation reminds unclear.

  8. Introduction7 (8/20) Recently Wirts & Johnson 2005: Argo Project has been rapidly easing the limitation. Seasonal/interannual upper ocean variability in the SE Bering Sea.

  9. Introduction9 (9/20) Purpose of this study Using Argo float data, we will discuss the formation and seasonal/interannual evolution of T-inversions in the entire subarctic NP.

  10. Data & Method1 (10/20) Data & Method T,S profiles recorded by Argo floats during May 2001 - December 2005.

  11. Data & Method Data & Method2 (11/20) Def of the magnitude of T-inversions (∆T) ∆T: defined as the largest temp. difference between all T-maxima and minima. One ∆T for one profile even the case of multiple T-inv

  12. Data & Method3 (12/20) Def of T-min outcrop T-min: considered to outcrop when the difference between T-min density & SSD < 0.03kg/m3.

  13. Magnitude of T-inversions (∆T) Results1 (13/20) 2002 Summer 2003 Summer 2004 Summer 2005 Summer

  14. Magnitude of T-inversions (∆T) Results2 (14/20) 2002 Summer Eastern Bering Sea 2003 Summer Eastern subartic NP Western subarctic NP 2004 Summer 2005 Summer

  15. Western subarcitc NP Results3 (15/20) T-max: constant T-min: seasonal variation cold in win <= outcrop & renewed every win warm in sum <= heated in sum from the surface => ∆T: seasonal variation => Same as Uda 1963 etc. ∆T: weak interannual variation => consistent with winter SST.

  16. Eastern Bering Sea Results4 (16/20) ∆T showed seasonality similar to that in the western SNP T-max: constant T-min: varies seasonally cold in win <= outcropped & renewed every win warm in sum <= summertime heating => ∆T: varies seasonally, => Same as Uda 1963 etc. In addition, interannual ∆T variation is consistent with winter SST. Results are consistent with those by Wirts & Johnson 2005

  17. Eastern subarcitc NP Results5 (17/20) ∆T: remarkable interannual variation large win02 … decreased until end of 2003 in 04 & 05 weak seasonal variation Because02WML thick&cold => T-min outcrop (large ∆T) 03WML thin&warm => T-min non-outcrop => T-min not renewed => ∆T decreased monotonically

  18. Eastern subarcitc NP Discussion1 (18/20) T-min&max: short-term fluctuation <= strong spatial variation <= eddies ∆T: small spatial variation => modest temporal variation => ∆T likely gives a more robust measure of the impact of wintertime coolingwhen using low resolution Argo array

  19. Discussion2 (19/20) Sitka Eddy Haida Eddy Warm & fresh Anti-cyclonic Diameter: 200km A composite SST emage (Thomson & Gower, 1998) Areas enclosed by eddis (Crawford, 2002) TS sections through Haida eddies (Whitney & Robert, 2002)

  20. Summary Argo data were analyzed to study seasonal/interannual variability of T-inversions in the whole subarctic NP (SNP). In the western SNP and Bering Sea, Tmin outcropped every winter, causing a seasonal cycle in ∆T. In the Gulf of Alaska in the eastern SNP, the Tmin outcropped in winters 02, 04 & 05, but scarcely outcropped in winter 03. Consequently, ∆T showed remarkable interannual variation. The year-to-year variation of ∆T in each region of the SNP was consistent with and thereby attributable to that of the winter SST anomaly there. Summary (20/20)

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