Arabian Sea response to monsoon variations

Publication Type  Journal Article
Year of Publication  2007
Authors  Murtugudde, R.; Seager, R.; Thoppil, P.
Journal Title  Paleoceanography
Volume  22
Issue  4
Pages  -
Journal Date  Dec 21
ISBN Number  0883-8305
Accession Number  ISI:000251883400001
Key Words  tropical indian-ocean; asian southwest monsoon; mixed-layer model; surface temperature; millennial-scale; variability; climate; dynamics; thermodynamics; circulation
Abstract  

This study aims to quantify the impact of strong monsoons on the mixed layer heat budget in the Arabian Sea by contrasting forced ocean general circulation model simulations with composite strong and weak monsoon winds. Strong (weak) monsoons are defined as years with zonal component of the Somali Jet being greater (smaller) by more than a standard deviation of the long-term mean of the National Centers for Environmental Prediction reanalysis winds. Coastal upwelling is shown to be demonstrably stronger for strong monsoons leading to significant surface cooling, shallower thermoclines, and deeper mixed layers. A coupled ecosystem model shows that surface chlorophyll, primary, and export production are indeed higher for strong monsoons compared to weak monsoons driven by the supply of colder, nutrient-rich waters from greater than 100 m depths. The surprising result is that a strong monsoon results in stronger negative wind stress curl away from the coasts and drives Ekman pumping that results in a deeper thermocline. The weaker stratification and larger turbulent kinetic energy from the winds drive deeper mixed layers leading entrainment cooling with some contribution from the advection of colder upwelled waters from the coastal upwelling regions. Thus the strong monsoons, in fact, enhance oceanic heat uptake indicating that ocean dynamics are cooling the surface and driving the lower atmosphere which has implications for the interpretation of monsoon variability from paleorecords.

Notes  

244RQTimes Cited:0Cited References Count:52

URL  <Go to ISI>://000251883400001
DOI  Doi 10.1029/2007pa001467