Variability of SST and ILD in the Arabian Sea and Sea of Oman in Association with the Monsoon Cycle

Abstract

Sea surface temperature (SST) and isothermal layer depth (ILD) are important oceanic parameters and could play a significant role in understanding the upper thermal structure as well as improve the predictive capability of monsoons in the tropical oceans. In a disparate departure from the past research, the present study investigates the seasonal variability of SST and ILD in association with the monsoon cycle in the Arabian Sea and Sea of Oman regions by examination of Argo datasets for 2016-17. In this study, the ILD climatology is determined from temperature profiles provided by the Argo floats based on a threshold technique T z ≥ SST − 1 ° C to investigate the region of stronger and weaker monsoon wind forcing. For SST, values of temperature are used nearest to the sea surface (depth z ≤ 5 m). The region is split into four distinct zones for an accurate description of the monsoon cycle: the south Arabian Sea, the central Arabian Sea, the north Arabian Sea, and the Sea of Oman. It is observed that summer monsoon is more pronounced in the south-central basin of the Arabian Sea, where ILD is deepening (>100 m in September 2016) mainly due to stronger wind forcing in this region. On the contrary, the Sea of Oman region is displayed with smaller ILD amplitude (<10 m in June 2016) with larger SST, meaning that this region is weakly influenced by the summer monsoon. The seasonal relationship established between ILD variability and monsoon cycle for 2016-17 shows that ILD could be a useful indicator for predicting summer monsoon in the Arabian Sea regions. Our analysis results indicate that the dynamics for SST variability are different in these regions and are influenced either by large-scale atmospheric forcing, such as the El Niño-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD), or by the effects of mesoscale variations occurring along the Oman-Arabian coast.

A study of forecast sensitivity to observations in the Bay of Bengal using LETKF

“…That is because the number of SST observations in the Arabian Sea exceeds that of the Bay of Bengal by a considerable margin (see Figures 5A, B) coupled with a more homogeneous representation of SST in the Arabian Sea (Figure 5G). In addition, the SST variability in the Arabian Sea is more pronounced than in the Bay of Bengal (Murtugudde et al, 2007;Khan et al, 2021). Feeding the SST observations likely improves the mesoscale variability of SST near the western boundary of the Arabian Sea and the variability of SST in the south-central part of the basin during summer monsoon.…”

Seasonal to Intraseasonal Variability of the Upper Ocean Mixed Layer in the Gulf of Oman

“…Overall, the observed variability in MLD suggests a strong seasonality regulated by atmospheric forcing, such as incoming solar radiation, winds, and freshwater flux (Kumar & Narvekar, 2005). During the sampling period El Niño was present, and previous studies have determined that ENSO can influence the air‐sea fluxes in the Arabian Sea (Currie et al., 2013; Moshozi & Bazrafshan, 2018; Khan et al., 2021). Despite this fact, ENSO variability is at large scales and interannual, yet as the study is focused on short and transient events at small spatial scale during the same year, its contribution is neglected.…”

Atmosphere-Ocean Coupled Variability in the Arabian/Persian Gulf

“…Owing to its strategic location and its susceptibility to extremely high temperatures and salinities (Johns et al, 2003;Khan et al, 2021), the Arabian Gulf (hereafter Gulf) is one of the most important, yet fragile, marine ecosystems on Earth. This important region may be susceptible to the adverse effects of climate change.…”