Mesoscale modeling study of the oceanographic conditions off the southwest coast of India

Haugen, Vibeke Eilen Jensen; Johannessen, Ola M.; Evensen, Geir

doi:10.1007/bf02701978

Cited by 16 publications

(7 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To circumvent this mystification, a driving force (alongshore winds) and its influence as an after effect (low sea surface temperature) has been emphasized. In southeastern Arabian Sea, the signatures of upwelling from the low sea level anomaly are noticeable from February / March itself (Johannessen et al 1987;Haugen et al 2002b), but the associated lowering of SST and an increase in productivity (Smitha et al 2008) is actually noticeable only with the onset of southwest monsoon winds which often occur by the end of May or early June. To decipher the intensity of upwelling, temperature gradients computed between the coastal ocean and at 5 degrees offshore along the same latitude and the Ekman offshore transport perpendicular to the coast was derived from the alongshore component of wind as computed by Nykaer and Camp (1994).…”

Section: Discussionmentioning

confidence: 96%

Interannual variability of upwelling indices in the Southeastern Arabian Sea: A satellite based study

et al. 2010

View full text Add to dashboard Cite

Increase in sea surface temperature with global warming has an impact on coastal upwelling. Past two decades (1988 to 2007) of satellite observed sea surface temperatures and space borne scatterometer measured winds have provided an insight into the dynamics of coastal upwelling in the southeastern Arabian Sea, in the global warming scenario. These high resolution data products have shown inconsistent variability with a rapid rise in sea surface temperature between 1992 and 1998 and again from 2004 to 2007. The upwelling indices derived from both sea surface temperature and wind have shown that there is an increase in the intensity of upwelling during the period 1998 to 2004 than the previous decade. These indices have been modulated by the extreme climatic events like El-Nino and Indian Ocean Dipole that happened during 1991-92 and 1997-98. A considerable drop in the intensity of upwelling was observed concurrent with these events. Apart from the impact of global warming on the upwelling, the present study also provides an insight into spatial variability of upwelling along the coast. Noticeable fact is that the intensity of offshore Ekman transport off 8 o N during the winter monsoon is as high as that during the usual upwelling season in summer monsoon. A drop in the meridional wind speed during the years 2005, 2006 and 2007 has resulted in extreme decrease in upwelling though the zonal wind and the total wind magnitude are a notch higher than the previous years. This decrease in upwelling strength has resulted in reduced productivity too.

show abstract

Section: Discussionmentioning

confidence: 96%

Interannual variability of upwelling indices in the Southeastern Arabian Sea: A satellite based study

et al. 2010

View full text Add to dashboard Cite

show abstract

“…At the 10°N section, the isotherms above 100 m exhibited shoaling at the coast. While all of the above studies reported upwelling due to wind-driven Ekman dynamics, numerical solutions suggest that upwelling-favorable Kelvin waves from the Bay of Bengal propagate into the eastern AS and modulate coastal circulation and SST along the WCI (McCreary et al, 1993;Haugen et al, 2002;Shankar et al, 2002).…”

Section: Upwellingmentioning

confidence: 95%

“…Cold, low-salinity water from the northern Bay of Bengal (BB) is also advected into the eastern AS by the Northeast Monsoon Current (Fig. 1(b)), which lowers SST along the WCI (Haugen et al, 2002). Cold SSTs that occur in the northern region have been attributed to convective cooling in the upper oceanic layers induced by dry continental winds (Banse, 1968).…”

Section: Ship-based Evidencementioning

confidence: 99%

Air-Sea Interaction, Coastal Circulation and Primary Production in the Eastern Arabian Sea: A Review

Luis

Kawamura

2004

Journal of Oceanography

View full text Add to dashboard Cite

Air-sea interaction, coastal circulation and primary production exhibit an annual cycle in the eastern Arabian Sea (AS). During June to September, strong southwesterly winds (4~9 m s -1 ) promote sea surface cooling through surface heat loss and vertical mixing in the central AS and force the West India Coastal Current equatorward. Positive wind stress curl induced by the Findlater jet facilitates Ekman pumping in the northern AS, and equatorward-directed alongshore wind stress induces upwelling which lowers sea surface temperature by about 2.5°C (compared to the offshore value) along the southwestern shelf of India and enhances phytoplankton concentration by more than 70% as compared to that in the central AS. During winter monsoon, from November to March, dry and weak northeasterly winds (2-6 m s -1 ) from the Indo-China continent enhance convective cooling of the upper ocean and deepen the mixed layer by more than 80 m, thereby increasing the vertical flux of nutrients in the photic layer which promotes wintertime phytoplankton blooms in the northern AS. The primary production rate integrated for photic layer and surface chlorophyll-a estimated from the Coastal Zone Color Scanner, both averaged for the entire western India shelf, increases from winter to summer monsoon from 24 to 70 g C m -2 month and from 9 to 24 mg m -2 , respectively. Remotely-forced coastal Kelvin waves from the Bay of Bengal propagate into the coastal AS, which modulate circulation pattern along the western India shelf; these Kelvin waves in turn radiate Rossby waves which reverse the circulation in the Lakshadweep Sea semiannually. This review leads us to the conclusion that seasonal monsoon forcing and remotely forced waves modulate the circulation and primary production in the eastern AS.

show abstract

“…Even eddy-permitting (e.g., Kawamiya, 2001;Kawamiya & Oschlies, 2003) and eddy-resolving (Haugen, Johannessen, & Evensen, 2002) models cannot be expected to reproduce the location and timing of specific biogeochemical events. In order to accurately depict mesoscale variability in the ocean interior, assimilation of satellite-observed SST and SSH (sea surface height) into eddy-resolving ocean general circulation models will be a necessity (Rochford, Kindle, Gallacher, & Weller, 2000).…”

Section: A Need To Resolve Open-ocean Eddy Variability (Eddies Reallymentioning

confidence: 99%

Monsoon-driven biogeochemical processes in the Arabian Sea

Wiggert

Hood

Banse

et al. 2005

Progress in Oceanography

230

171

View full text Add to dashboard Cite

Although it is nominally a tropical locale, the semiannual wind reversals associated with the Monsoon system of the Arabian Sea result annually in two distinct periods of elevated biological activity. While in both cases monsoonal forcing drives surface layer nutrient enrichment that supports increased rates of primary productivity, fundamentally different entrainment mechanisms are operating in summer (Southwest) and winter (Northeast) Monsoons. Moreover, the intervening intermonsoon periods, during which the region relaxes toward oligotrophic conditions more typical of tropical environments, provide a stark contrast to the dynamic biogeochemical activity of the monsoons. The resulting spatial and temporal variability is great and provides a significant challenge for ship-based surveys attempting to characterize the physical and biogeochemical environments of the region. This was especially true for expeditions in the pre-satellite era. Here, we present an overview of the dynamical response to seasonal monsoonal forcing and the characteristics of the physical environment that fundamentally drive regional biogeochemical variability. We then review past observations of the biological distributions that provided our initial insights into the pelagic system of the Arabian Sea. These evolved through the 1980s as additional methodologies, in particular the first synoptic ocean color distributions gathered by the Coastal Zone Color Scanner, became available. Through analyses of these observations and the first large-scale physical-biogeochemical modeling attempts, a pre-JGOFS understanding of the Arabian Sea emerged. During the 1 990s, the in situ and remotely sensed observational databases were significantly extended by regional JGOFS activities and the onset of Sea-viewing Wide Field-of-View Sensor ocean color measurements. Analyses of these new data and coupled physical-biogeochemical models have already advanced our understanding and have led to either an amplification or revision of the pre-JGOFS paradigms. Our understanding of this complex and variable ocean region is still evolving. Nonetheless, we have a much better understanding of time-space variability of biogeochemical properties in the Arabian Sea and much deeper insights about the physical and biological factors that drive them, as well as a number of challenging new directions to pursue. The publl reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, Sjlfhering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of htfcrmsti n, including suggestions for reducing the burden, to the Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents should be aware tbsn notiithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a...

show abstract

Mesoscale modeling study of the oceanographic conditions off the southwest coast of India

Cited by 16 publications

References 19 publications

Interannual variability of upwelling indices in the Southeastern Arabian Sea: A satellite based study

Interannual variability of upwelling indices in the Southeastern Arabian Sea: A satellite based study

Air-Sea Interaction, Coastal Circulation and Primary Production in the Eastern Arabian Sea: A Review

Monsoon-driven biogeochemical processes in the Arabian Sea

Contact Info

Product

Resources

About