Modeling the Barrier-Layer Formation in the Southeastern Arabian Sea*

Abstract

The effect of salinity on the formation of the barrier layer (BL) in the South-Eastern Arabian Sea (SEAS) is investigated using an ocean general circulation model. In accordance with previous studies, the runoff distribution and the India-Sri Lanka passage have a strong impact on the realism of the salinity simulated in the area at seasonal time scales. The model simulates a BL pattern in fairly good agreement with available observations. Eulerian and Lagrangian approaches show that the BL is formed by two complementary processes, the arrival of low-salinity surface waters that are cooled en route to the SEAS and downwelling of waters mostly local to the SEAS in the subsurface layers. The surface waters are partly of Bay-of-Bengal origin and are partly from the SEAS, but are cooled east and south of Sri Lanka in the model. That the downwelled subsurface waters are warm and are not cooled leads to temperature inversions in the BL. The main forcing for this appears to be remotelyforced planetary waves.

A new atlas of temperature and salinity for the North Indian Ocean

“…examination of the bathymetry in the region rules out a large transport through this gap (Durand et al 2007). Recent modelling results suggest that a possible reason for this model deficiency is the coarse resolution of earlier studies; the EICC is too weak in a model with a horizontal resolution of 0.5…”

“…One problem faced by numerical modellers has been the inability of models to simulate the poleward extent of the low-salinity water during winter along the Indian west coast (Han and McCreary 2001;Durand et al 2007;Kurian and Vinayachandran 2007). The difficulty in getting the models to match the poleward penetration seen in the Levitus climatologies (figure 8) led to some modellers arguing in favour of a substantial flow of the low-salinity water of Bay-of-Bengal origin through the shallow Adam's-Bridge region in the gap between India and Sri Lanka (Han and McCreary 2001), but an NIOA NIOAW09 KESSLER Figure 19.…”

“…This low salinity is a consequence of inflow of fresher water from the Bay of Bengal (Shetye et al , 1996Shetye 1993;Rao and Sivakumar 1999;Shenoi et al 1999;Han and McCreary 2001;Durand et al 2004Durand et al , 2007Kurian and Vinayachandran 2007). In November, when the low-salinity water enters the SEAS from the Bay of Bengal, the poleward penetration, along the west coast, of this low-salinity water is greater in NIOA than in WOA09 (figure 8).…”

Holocene evolution of summer winds and marine productivity in the tropical Indian Ocean in response to insolation forcing: data-model comparison

“…The circulation at the tip of India is affected by a fresh water current from the Bay of Bengal (e.g., Durand et al, 2007). The fresh water is advected in winter by the westward flowing, North Equatorial Current (NEC).…”

Validation of a hybrid coordinate ocean model for the Indian Ocean

“…The barrier layer (BL) formations in the Indian Ocean have been modelled by Masson et al 14,15 They used a coupled model to evaluate the effect of BL on the sea surface temperature (SST) and on the monsoon onset in the SEAS 14 and in another study studied the BL formation in the eastern equatorial Indian Ocean (EIO). 15 The effect of salinity on the generation of the BL in the SEAS is analysed employing an ocean general circulation model by Durand et al 16 Numerous studies have been done about Indian Ocean warm pool and in one recent study the mechanisms and formation of Arabian Sea mini warm pool is discussed by Kurian and Vinayachandran. 17 Most of the earlier models were based on reduced gravity model structure, while as many of the recent models are based on versions of Geophysical Fluid Dynamics Laboratory (GFDL), Modular Ocean Model (MOM).…”