Coupled sea surface temperature–seawater δ18O reconstructions in the Arabian Sea at the millennial scale for the last 35 ka

Two sediment cores from the western (905; 10.46°9′N, 51.56°4′E, water depth 1586 m) and eastern (SK17; 15°15′N, 72°58′E, water depth 840 m) Arabian Sea were used to study past sea surface temperatures (SST) and seawater δ 18O (δ 18Ow) variations for the past 35 ka. We used coupled Mg/Ca-δ 18O calcite variability in two planktonic foraminiferal species: Globigerinoides ruber, which thrives throughout the year, and Globigerina bulloides, which occurs mainly when surface waters contain high nutrients during upwelling or convective mixing. SSTs in both areas based on Mg/Ca in G. ruber were ∼3 to 4°C lower during the Last Glacial Maximum (LGM; ∼21 ka) than today and the Holocene period. The SST records based on G. bulloides also indicate general cooling, down to 18°C in both areas. SSTs in the western Arabian Sea based on G. bulloides were always lower than those based on G. ruber, indicating the presence of strong seasonal temperature contrast during the Holocene and LGM. We interpret the consistent presence of this seasonal temperature contrast to reflect a combination of seasonal summer upwelling (SW monsoon) and winter convective mixing (NE monsoon) in the western Arabian Sea. In the eastern Arabian Sea, G. bulloides-based SSTs were slightly lower (about 1°C) than G. ruber-based SSTs during the Holocene, indicating the almost absence of a seasonal temperature gradient, similar to today. However, a large seasonal temperature contrast occurred during the LGM which favors the assumption that strong NE monsoon winds forced winter upwelling or convective mixing offshore Goa. SST and δ 18Ow reconstructions reveal evidence of millennial-scale cycles, particularly in the eastern Arabian Sea. Here, the stadial periods (Northern Hemisphere cold periods such as Younger Dryas and Heinrich events) are marked by increasing SSTs and salty sea surface conditions relative to those during the interstadial periods. Indeed, the δ 18Ow record shows evidence of low-saline surface waters during interstadial periods, indicating increased freshwater runoff from the Western Ghats as a consequence of enhanced SW monsoon intensity.

[1]  D. Kroon,et al.  Sea surface temperatures of the western Arabian Sea during the last deglaciation , 2007 .

[2]  A. Singh,et al.  Millennial scale variations in productivity and OMZ intensity in the Eastern Arabian Sea , 2006 .

[3]  Stefan Schouten,et al.  Reconstruction of sea surface temperature variations in the Arabian Sea over the last 23 kyr using organic proxies (TEX86 and U37K , 2006 .

[4]  D. Oppo,et al.  Sea surface temperature pattern reconstructions in the Arabian Sea , 2006 .

[5]  R. Ganeshram,et al.  Variations in tropical convection as an amplifier of global climate change at the millennial scale [rapid communication] , 2005 .

[6]  B. Malmgren,et al.  Seasonal sea surface temperature contrast between the Holocene and last glacial period in the western Arabian Sea (Ocean Drilling Project Site 723A): Modulated by monsoon upwelling , 2005 .

[7]  T. Herbert,et al.  A solar (irradiance) trigger for millennial-scale abrupt changes in the southwest monsoon? , 2004 .

[8]  K. Arrigo,et al.  The interplay between upwelling and deep convective mixing in determining the seasonal phytoplankton dynamics in the Gulf of Aqaba: Evidence from SeaWiFS and MODIS , 2003 .

[9]  H. Elderfield,et al.  A study of cleaning procedures used for foraminiferal Mg/Ca paleothermometry , 2003 .

[10]  F. Sirocko.  Global change: Ups and downs in the Red Sea , 2003, Nature.

[11]  Henry Elderfield,et al.  Calibration of Mg/Ca thermometry in planktonic foraminifera from a sediment trap time series , 2003 .

[12]  J. Overpeck,et al.  Abrupt changes in the Asian southwest monsoon during the Holocene and their links to the North Atlantic Ocean , 2003, Nature.

[13]  F. Peeters,et al.  The effect of upwelling on the distribution and stable isotope composition of Globigerina bulloides and Globigerinoides ruber (planktic foraminifera) in modern surface waters of the NW Arabian Sea , 2002 .

[14]  J. Overpeck,et al.  Increase in the Asian Southwest Monsoon During the Past Four Centuries , 2002, Science.

[15]  G. Reichart,et al.  Synchroneity of oxygen minimum zone intensity on the Oman and Pakistan margins at sub-Milankovitch time scales , 2002 .

[16]  H. Elderfield,et al.  An intensity ratio calibration method for the accurate determination of Mg/Ca and Sr/Ca of marine carbonates by ICP‐AES , 2002 .

[17]  N. Shackleton,et al.  The 100,000-year ice-Age cycle identified and found to lag temperature, carbon dioxide, and orbital eccentricity , 2000, Science.

[18]  H. Elderfield,et al.  Past temperature and δ18O of surface ocean waters inferred from foraminiferal Mg/Ca ratios , 2000, Nature.

[19]  R. Ramesh,et al.  High resolution Holocene monsoon record from the eastern Arabian Sea , 2000 .

[20]  E. Bard,et al.  Planktonic Foraminiferal and Alkenone Records of the Last Deglaciation from the Eastern Arabian Sea , 1999, Quaternary Research.

[21]  H. Schulz,et al.  Correlation between Arabian Sea and Greenland climate oscillations of the past 110,000 years , 1998 .

[22]  Jelle Bijma,et al.  Reevaluation of the oxygen isotopic composition of planktonic foraminifera: Experimental results and revised paleotemperature equations , 1998 .

[23]  E. Bard,et al.  Interhemispheric synchrony of the last deglaciation inferred from alkenone palaeothermometry , 1997, Nature.

[24]  E. Bard,et al.  Deglacial sea-level record from Tahiti corals and the timing of global meltwater discharge , 1996, Nature.

[25]  D. Anderson,et al.  Sea-Surface Temperatures and the History of Monsoon Upwelling in the Northwest Arabian Sea during the Last 500,000 Years , 1995, Quaternary Research.

[26]  W. Prell,et al.  Climate-related variations in denitrification in the Arabian Sea from sediment 15N/14N ratios , 1995, Nature.

[27]  B. Malmgren,et al.  Monsoon upwelling effects on test size of some planktonic foraminiferal species from the Oman Margin, Arabian Sea , 1995 .

[28]  E. Bard,et al.  Reconstructing sea surface temperature and salinity using δ18O and alkenone records , 1993, Nature.

[29]  J. Duplessy,et al.  Century-scale events in monsoonal climate over the past 24,000 years , 1993, Nature.

[30]  D. Anderson,et al.  A 300 KYR Record of Upwelling Off Oman during the Late Quaternary: Evidence of the Asian Southwest Monsoon , 1993 .

[31]  E. Jansen,et al.  A high‐resolution diatom record of the last deglaciation from the SE Norwegian Sea: Documentation of rapid climatic changes , 1992 .

[32]  F. Sirocko,et al.  Organic carbon accumulation rates in the Holocene and glacial Arabian Sea: implications for O2-consumption in the deep-sea and atmospheric CO2 variations , 1992 .

[33]  S. Clemens,et al.  Forcing mechanisms of the Indian Ocean monsoon , 1991, Nature.

[34]  V. Ittekkot,et al.  Increased particle flux to the deep ocean related to monsoons , 1989, Nature.

[35]  J. Duplessy,et al.  Retreat velocity of the North Atlantic polar front during the last deglaciation determined by 14C accelerator mass spectrometry , 1987, Nature.

[36]  Karl Banse,et al.  Seasonality of phytoplankton chlorophyll in the central and northern Arabian sea , 1987 .

[37]  J. Duplessy,et al.  Variations of the monsoon regime during the upper quaternary: Evidence from carbon isotopic record of organic matter in North Indian Ocean sediment cores , 1986 .

[38]  Jijun Zhang.  Living planktonic foraminifera from the eastern Arabian Sea , 1985 .

[39]  J. L. Cullen,et al.  Planktonic foraminifera of the northern Indian Ocean: Distribution and preservation in surface sediments , 1984 .

[40]  J. Duplessy.  Glacial to interglacial contrasts in the northern Indian Ocean , 1982, Nature.

[41]  B. Molfino,et al.  Surface Circulation of the Indian Ocean during the Last Glacial Maximum, Approximately 18,000 yr B.P. , 1980, Quaternary Research.

[42]  J. Blanton.  VERTICAL ENTRAINMENT INTO THE EPILIMNIA OF STRATIFIED LAKES , 1973 .

[43]  G. Reichart,et al.  Centennial-millennial-scale monsoon variations off Somalia over the last 35 ka , 2002, Geological Society, London, Special Publications.

[44]  G. Brummer,et al.  Fluxes of planktic foraminifera in response to monsoonal upwelling on the Somalia Basin margin. , 2000 .

[45]  E. Bard,et al.  Sea surface temperature and productivity records for the past 240 kyr in the Arabian Sea , 1997 .

[46]  E. Rohling,et al.  Red Sea outflow during the last glacial maximum , 1996 .

[47]  D. Anderson,et al.  The oxygen-isotope composition of tropical ocean surface water during the last deglaciation , 1993 .

[48]  J. L. Cullen.  Microfossil evidence for changing salinity patterns in the bay of Bengal over the last 20 000 years , 1981 .

[49]  A. Mcintyre,et al.  The North Atlantic Ocean during the last deglaciation , 1981 .

[50]  A. Mcintyre,et al.  Seasonal reconstructions of the earth's surface at the last glacial maximum , 1981 .

[51]  S. Gorshkov,et al.  World ocean atlas , 1976 .

[52]  K. Wyrtki,et al.  Physical Oceanography of the Indian Ocean , 1973 .