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Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002-2008

DRS at CSIR-National Institute of Oceanography

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Title Observed intra-seasonal to interannual variability of the upper ocean thermal structure in the southeastern Arabian Sea during 2002-2008
 
Creator Gopalakrishna, V.V.
Durand, F.
Nisha, K.
Lengaigne, M.
Boyer, T.P.
Costa, J.
Rao, R.R.
Ravichandran, M.
Amrithash, S.
John, L.
Girish, K.
Ravichandran, C.
Suneel, V.
 
Subject XBT data
Interannual variability
Intra-seasonal variability
Arabian Sea
 
Description The southeastern Arabian Sea (SEAS), located in the Indian Ocean warmpool, is a key-region of the regional climate system. It is suspected to play an important role in the dynamics of the Asian summer monsoon system. The present study reports the salient features derived from a newly harvested observational dataset consisting of repeated fortnightly XBT transects in the SEAS over the period 2002-2008. The fortnightly resolution of such a multi-year record duration is unprecedented in this part of the world ocean and provides a unique opportunity to examine the observed variability of the near-surface thermal structure over a wide spectrum, from intra-seasonal to interannual timescales. It found that most of the variability is trapped in the thermocline, taking the form of upwelling and downwelling motions of the thermal stratification. The seasonal variations are consistent with past studies and confirm the role of the monsoonal wind forcing through linear baroclinic waves (coastally-trapped Kelvin and planetary Rossby waves). Sub-seasonal variability takes the form of anomalous events lasting a few weeks to a few months and occurs at two preferred timescales: in the 30-110 day band, within the frequency domain of the Madden-Julian oscillation and in the120-180 day band. While this sub-seasonal variability appears fairly barotropic in the offshore region, the sign of the anomaly in the upper thermocline is opposite to that in its lower part on many occasions along the coast. Our dataset also reveals relatively large interannual temperature variations of about 1 degrees C from 50 to 200 m depth that reflect a considerable year-to-year variability of the magnitude of both upwelling and downwelling events. This study clearly demonstrates the necessity for sustained long-term temperature measurements in the SEAS
 
Date 2010-06-14T10:15:08Z
2010-06-14T10:15:08Z
2010
 
Type Journal Article
 
Identifier Deep-Sea Research I, vol.57(6); 739-754
http://drs.nio.org/drs/handle/2264/3631
 
Language en
 
Rights An edited version of this paper was published by Elsevier. Copyright [2010] Elsevier
 
Publisher Elsevier