Hyperstratification following glacial overturning events in the northern Arabian Sea

Abstract

[1] Correlations between Arabian Sea organic carbon and GISP2 d 18 O records indicate a pronounced oxygen minimum zone (OMZ) during interstadials, whereas well-oxygenated conditions prevailed during stadials. Local deep winter mixing ventilated intermediate water during the coldest stadials, corresponding to North Atlantic Heinrich events. Here we show that in the Arabian Sea periods of climatic warming following Heinrich events H6-H4 and the Younger Dryas (YD) are characterized by dominant Polysphaeridium zoharyi (dinoflagellate) cysts. The finding of assemblages dominated by P. zoharyi in the open ocean is unusual because today similar assemblages are restricted to lagoonal settings. It is postulated that the highly saline mixed layer and the strong density gradient which characterized Arabian Sea hydrography after H6-H4 and the YD simulated a shallow seafloor, thereby enabling germination of cysts prior to sinking. The strong density gradient following cold stadials should have facilitated the rapid reestablishment of a pronounced OMZ during interstadials.

Sedimentary trace element records over the last 200 kyr from within and below the northern Arabian Sea oxygen minimum zone

“…The profiles of Mn show maxima in between these OC maxima. Smaller scale rapid oscillations are probably related to higher frequency climate changes such as the DO cycles (Reichart et al, 1998;Reichart and Brinkhuis, 2003;Reichart et al, 2004).…”

Eustatic variations during the Paleocene‐Eocene greenhouse world

“…In addition, we use the abundance of members of the Goniodomaceae family, here represented by Eocladopyxis and Polysphaeridium spp. These taxa are tolerant to highly variable salinities and are mainly recorded in lagoons and coastal margins [Bradford and Wall, 1984;Brinkhuis, 1994;Reichart et al, 2004;Pross and Brinkhuis, 2005].…”

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

“…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.…”

“…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.…”