Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

Pourmand, A.; Marcantonio, Franco; Schulz, Hartmut

doi:10.1016/s0012-821x(04)00109-8

Cited by 77 publications

(95 citation statements)

References 48 publications

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“…3c; northwesterly at the surface (not shown)). This weakening of the southeast trade winds that cross the Equator reduces upwelling in the Arabian Sea (where there are weaker southwesterly winds), as also suggested by proxy records from this region 25 . Moreover, strengthening of the eastward winds over the Equator, a unique feature in the Indian Ocean responsible for warm equatorial waters, also contributes to the warming in the eastern tropical Indian Ocean.…”

supporting

confidence: 58%

North Atlantic forcing of tropical Indian Ocean climate

Mohtadi

Prange

Oppo

et al. 2014

Nature

245

228

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The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells 1-5 , but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.In the North Atlantic, the most recent glacial and deglacial periods are characterized by a series of abrupt and severe cold snaps of millennial duration associated with either iceberg instabilities and surges (Heinrich events) or freshwater input from the Arctic Ocean 6 (the Younger Dryas). These abrupt events are of particular interest because they were rapidly communicated through the ocean by a slowdown, or potentially a shutdown, of the Atlantic meridional overturning circulation 7 (AMOC) and through the atmospheric circulation 8 causing climate anomalies worldwide. Climate archives document a significant tropical hydrologic response to these events. Dry Younger Dryas and Heinrich stadials have been reported from various marine and terrestrial archives across the tropical Indian Ocean 4,9-14 .However, a few records suggest wet Younger Dryas or Heinrich stadials over northeast Australia 15 , southern Indonesia 5,16 and southeast Africa 12,17 . Although there seems to be strong evidence that the intertropical convergence zone (ITCZ) moved southwards in the tropical Atlantic 2 , a wide range of mechanisms have been offered to explain the connection between the cooling of the North Atlantic and tropical Indian Ocean hydroclimates: a weakening of the rainfall system in response to regional sea surface cooling 13,14 ; and changes in the monsoon intensity 4,10,16 associated with a southward shift in the mean 1 or winter 4,5,15 position of the ITCZ or in the position of oceanic fronts 18 .How...

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supporting

confidence: 58%

North Atlantic forcing of tropical Indian Ocean climate

Mohtadi

Prange

Oppo

et al. 2014

Nature

245

228

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“…The value of 0.45 ± 0.05 is considerably lower than that used in previous studies in the Indian Ocean [Marcantonio et al, 2001;Pourmand et al, 2004] derived from the average crustal value of 0.8 ± 0.2 [Anderson et al, 1990;Taylor, 1964]. The new value for the Indian Ocean lies within the estimate of 0.4 ± 0.1 for the Southern Ocean, south of the Antarctic Polar Front [Walter et al, 1997].…”

Section: Detrital Provenancementioning

confidence: 38%

Constant bottom water flow into the Indian Ocean for the past 140 ka indicated by sediment ²³¹Pa/²³⁰Th ratios

2007

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A down‐core 231Pa/230Th record has been measured from the southwestern Indian Ocean to reconstruct the history of deep water flow into this basin over the last glacial‐interglacial cycle. The (231Paxs/230Thxs)0 ratio throughout the record is nearly constant at approximately 0.055, significantly lower than the production ratio of 0.093, indicating that the proxy is sensitive to changes in circulation and/or sediment flux at this site. The consistent value suggests that there has been no change in the inflow of Antarctic Bottom Water to the Indian Ocean during the last 140 ka, in contrast to the changes in deep circulation thought to occur in other ocean basins. The stability of the (231Paxs/230Thxs)0 value in the record contrasts with an existing sortable silt () record from the same core. The observed variability is attributed to a local geostrophic effect amplifying small changes in circulation. A record of authigenic U from the same core suggests that there was reduced oxygen in bottom waters at the core locality during glacial periods. The consistency of the (231Paxs/230Thxs)0 record implies that this could not have arisen by local changes in productivity, thus suggesting a far‐field control: either globally reduced bottom water oxygenation or increased productivity south of the Opal Belt during glacials.

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“…The sedimentary sequence of the Murray Ridge provides an excellent archive of past primary productivity and Indian summer monsoon intensity (Pourmand et al, 2004;Reichart et al, 1997Reichart et al, , 1998Reichart et al, , 2004Schulz et al, 1998). IMAGES Core MD04-2881 was recovered on 14 October 2004, from a water depth of 2387 m at the Murray Ridge (22 • 12 .5 N -63 • 05 .5 E) (Fig.…”

Section: Sediment Core Md04-2881mentioning

confidence: 99%

“…The main aim of the investigation of this core was to investigate the paleoceanographic changes in the Arabian Sea during the MPT, since numerous studies only document these in great detail from the past 400 000 years (Almogi-Labin et al, 2000;Altabet et al, 2002;Anderson et al, 2002;Budziak et al, 2000;Clemens et al, 1991;Prell, 1990, 2003;Emeis et al, 1995;Gupta et al, 2003;Ishikawa and Motoyoshi, 2007;Ivanova et al, 2003;Jaeschke et al, 2009;Sirocko, 2000, 2003;Lückge et al, 2001;Naidu and Malmgren, 1996;Naidu, 2006;Pattan et al, 2003;Prabhu and Shankar, 2005;Prell et al, 1980;Prell and Campo, 1986;Prell and Kutzbach, 1992;Reichart et al, 1997Reichart et al, , 1998Reichart et al, , 2002Reichart et al, , 2004Rostek et al, 1993Rostek et al, , 1997Saher et al, 2007;Sarkar et al, 1990;Schmiedl and Leuschner, 2005;Schulte et al, 1999;Schulz et al, 1998;Sirocko et al, 1993Sirocko et al, , 1996Wang et al, 2005a). Using a multi-proxy approach, we will report on the complex interplay of summer monsoon upwelling-related productivity changes, OMZ intensity, glacial-interglacial variability in intermediate water contributions, supralysoclinal carbonate dissolution and winter monsoon-related deep-mixing events.…”

Section: Introductionmentioning

confidence: 99%

High Arabian Sea productivity conditions during MIS 13 – odd monsoon event or intensified overturning circulation at the end of the Mid-Pleistocene transition?

et al. 2010

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Abstract. Marine isotope stage (MIS) 13 (∼500 000 years ago) has been recognized as atypical in many paleoclimate records and, in particular, it has been connected to an exceptionally strong summer monsoon throughout the Northern Hemisphere. Here, we present a multi-proxy study of a sediment core taken from the Murray Ridge at an intermediate water depth in the northern Arabian Sea that covers the last 750 000 years. Our results indicate that primary productivity conditions were anomalously high during MIS 13 in the Arabian Sea and led to extreme carbonate dissolution and glauconitization in the deep-sea sediments. These observations could be explained by increased wind driven upwelling of nutrient-rich deep waters and, hence, by the occurrence of an exceptionally strong summer monsoon event during MIS 13, as it was suggested in earlier studies. However, ice core records from Antarctica demonstrate that atmospheric methane concentrations, which are linked to the extent of tropical wetlands, were relatively low during this period. This constitutes a strong argument against an extremely enhanced global monsoon circulation during MIS 13 which, moreover, is in contrast with results of transient climate modelling experiments. As an alternative solution for the aberrant conditions in the Arabian Sea record, we propose that the high primary productivity was probably related to the onset of an intensive meridional overturning circulation in the Atlantic Ocean at the end of the Mid-Pleistocene transition. This may have led to an increased supply of nutrient-rich deep waters into the Indian Ocean euphotic zone, thereby triggering the observed productivity maximum.

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Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

Cited by 77 publications

References 48 publications

North Atlantic forcing of tropical Indian Ocean climate

North Atlantic forcing of tropical Indian Ocean climate

Constant bottom water flow into the Indian Ocean for the past 140 ka indicated by sediment ²³¹Pa/²³⁰Th ratios

High Arabian Sea productivity conditions during MIS 13 – odd monsoon event or intensified overturning circulation at the end of the Mid-Pleistocene transition?

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Variations in productivity and eolian fluxes in the northeastern Arabian Sea during the past 110 ka

Cited by 77 publications

References 48 publications

North Atlantic forcing of tropical Indian Ocean climate

North Atlantic forcing of tropical Indian Ocean climate

Constant bottom water flow into the Indian Ocean for the past 140 ka indicated by sediment 231Pa/230Th ratios

High Arabian Sea productivity conditions during MIS 13 – odd monsoon event or intensified overturning circulation at the end of the Mid-Pleistocene transition?

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Product

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About

Constant bottom water flow into the Indian Ocean for the past 140 ka indicated by sediment ²³¹Pa/²³⁰Th ratios