Potential new production in two upwelling regions of the western Arabian Sea: Estimation and comparison

Abstract

Using satellite‐derived and in situ data, the wind‐driven potential new production (nitrate supply) for the 300 km wide coastal band in two upwelling regions of the western Arabian Sea (AS) during the southwest monsoon is estimated. The upward nitrate flux to the euphotic zone is generally based on the physical processes of coastal transport (Ekman transport and geostrophic transport) and offshore Ekman pumping. The coastal geostrophic current in the western AS influences the upwelling intensity and latitudinal distributions of nitrate supply. The Oman and Somalia upwelling regions have similar level of potential new production (nitrate supply) during the summer monsoon, while the satellite estimates of primary production off Oman are 2 times greater than those off Somalia. The much higher potential f‐ratio in the Somalia upwelling region indicates that the primary production could be limited by availability of other macronutrients (e.g., silicate). The correlation analysis of the primary production and the aerosol optical thickness shows that the Oman upwelling region displays a stronger coupling between the atmospheric deposition and the phytoplankton abundance. The high summertime dust levels in the atmosphere are suggested to contribute to the high primary production in the Oman upwelling region.

Evaluation of Water Residence Time, Submarine Groundwater Discharge, and Maximum New Production Supported by Groundwater Borne Nutrients in a Coastal Upwelling Shelf System

“…The nutricline was mainly located about 35 m in the eastern Hainan shelf, with relatively smaller values at the inner shelf and larger values at the out shelf areas. This phenomenon also suggests the nutrient is supplied to the euphotic zones by the coastal upwelling (especially by Ekman transport) at the nearshore areas, as indicated in other biogeochemical studies of the coastal upwelling systems (Chavez & Messié, ; Liao et al, ; Messié & Chavez, ; Messié et al, ). DIN and DIP are further plotted on the T‐S isopycnal to reveal nutrient dynamics in different water masses (Figures b and c).…”

“…The eastern Hainan shelf is intensively influenced by coastal upwelling, which delivers significant amount of nuclides and nutrients to the upper mixing layer. Generally, coastal upwelling in the eastern Hainan comprises of two components: (1) Ekman transport ( ) driven by along shore wind stresses; (2) Ekman pumping ( ) driven by cyclonic wind stress curl (Chavez & Messié, ; Hu & Wang, ; Liao et al, ; Messié et al, ). Ekman transport is speculated to occur within the Rossby radius of deformation (Allen, ; Bakun & Nelson, ).…”

“…(2) Ekman Journal of Geophysical Research: Oceans 10.1002/2017JC013398 pumping (v EK2P ) driven by cyclonic wind stress curl Hu & Wang, 2016;Liao et al, 2016;Messi e et al, 2009). Ekman transport is speculated to occur within the Rossby radius of deformation (Allen, 1973;Bakun & Nelson, 1991).…”

Biological production in the Indian Ocean upwelling zones –Part 1: refined estimation via the use of a variable compensation depth in ocean carbon models

“…Arabian Sea production is not just limited by nutrients but also by the dust input . The dust-induced primary production in the WAS, especially over the Oman coast, is noted during August (Liao et al, 2016). The mesoscale variability in the circulation and its impact on production and carbon cycle are also limiting factors in this model as noted above.…”

“…The Arabian Sea is known for having the second largest Tuna fishing region in the Indian Ocean (Lee et al, 2005). The Somali and Omani upwelling regions experience phytoplankton blooms that are prominent, with net primary production (NPP) exceeding 435 g C m −2 yr −1 (Liao et al, 2016). On the other hand productivity over the SLD (Vinayachandran and Yamagata, 1998) is triggered by open-ocean Ekman suction with strong Chl a blooms during the summer monsoon Vinayachandran et al, 2004).…”