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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

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)

horizontal distribution

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

formation of t inversions 1 2

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)

formation of t inversions 2 2

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.

t inversion as a heat reservoir

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

previous studies

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.

wirts johnson 2005

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.

purpose of this study

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.

data method1 10 20
Data & Method1 (10/20)

Data & Method

T,S profiles recorded by Argo floats

during May 2001 - December 2005.

data method2 11 20

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

data method3 12 20
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.

results1 13 20

Magnitude of T-inversions (∆T)

Results1 (13/20)

2002 Summer

2003 Summer

2004 Summer

2005 Summer

results2 14 20

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

results3 15 20

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.

results4 16 20

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

results5 17 20

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

discussion1 18 20

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

discussion2 19 20
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)

summary 20 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)