Last Glacial Maximum to Holocene sea surface conditions at Umnak Plateau, Bering Sea, as inferred from diatom, alkenone, and stable isotope records

Abstract

[1] The Bering Sea gateway between the Pacific and Arctic oceans impacts global climate when glacialinterglacial shifts in shore line position and ice coverage change regional albedo. Previous work has shown that during the last glacial termination and into the Holocene, sea level rises and sea ice coverage diminishes from perennial to absent. Yet, existing work has not quantified sea ice duration or sea surface temperatures (SST) during this transition. Here we combine diatom assemblages with the first alkenone record from the Bering Sea to provide a semiquantitative record of sea ice duration, SST, and productivity change since the Last Glacial Maximum (LGM). During the LGM, diatom assemblages indicate that sea ice covered the southeastern Bering Sea perennially. At 15.1 cal ka B.P., the diatom assemblage shifts to one more characteristic of seasonal sea ice and alkenones occur in the sediments in low concentrations. Deglaciation is characterized by laminated intervals with highly productive and diverse diatom assemblages and inferred high coccolithophorid production. At 11.3 cal ka B.P. the diatom assemblage shifts from one dominated by sea ice species to one dominated by a warmer water, North Pacific species. Simultaneously, the SST increases by 3°C and the southeastern Bering Sea becomes ice-free year-round. Productivity and temperature proxies are positively correlated with independently dated records from elsewhere in the Bering Sea, the Sea of Okhotsk, and the North Pacific, indicating that productivity and SST changes are coeval across the region.

Centennial to millennial climate variability in the far northwestern Pacific (off Kamchatka) and its linkage to the East Asian monsoon and North Atlantic from the Last Glacial Maximum to the early Holocene

“…The timing of the decrease in the sea ice cover since ∼ 15.3 ka is consistent with the regional surface water warming (Max et al, 2012). Such a pattern in productivity changes in the N Pacific and the Bering Sea during the glacial-interglacial transitions has been reported in previous studies (Caissie et al, 2010;Galbraith et al, 2007;Gebhardt et al, 2008;Gorbarenko, 1996;Keigwin, 1998) and was likely a persistent feature of the N Pacific and its realm, forced by the resumption of the AMOC at the B/A warming.…”

“…The abovementioned patterns of climate variability during the LGM-EH in moderate-high latitudes of the Northern Hemisphere is consistent with the N Pacific and its marginal seas, evidenced by the alkenone-derived SST (Barron et al, 2003;Max et al, 2012) and pollen records (Gorbarenko et al, 2003(Gorbarenko et al, , 2004. The significant increase in productivity in the NW Pacific during the B/A was likely achieved by additional nutrient input into the euphotic layer due to accelerated sea level rise (Siddall et al, 2010) accompanied by the supply of organic matter from the submerged shelf and by prolonged blooming season due to the warming, which is a common paleoceanography feature of the N Pacific and its marginal seas (Barron et al, 2003(Barron et al, , 2009Caissie et al, 2010;Galbraith et al, 2007;Gorbarenko, 1996;Gorbarenko and Goldberg, 2005;Keigwin, 1998;Keigwin et al, 1992;Max et al, 2012;Seki et al, 2004).…”

“…These model and proxy studies suggested either in-phase relationships of deglacial variability between the North (N) Atlantic and NW Pacific (Caissie et al, 2010;Chikamoto et al, 2012;Kienast and McKay, 2001;Seki et al, 2002) or out-of-phase responses (Gebhardt et al, 2008;Sarnthein et al, 2006). The in-phase relationship has been attributed to rapid atmospheric teleconnections in the Northern Hemisphere on a decadal timescale (Max et al, 2012).…”

“…Recent studies on high-resolution and well-dated sediment cores from the subarctic NW Pacific, the Okhotsk Sea, and the western Bering Sea show the variations in SST during the last deglaciation similar to the NE Pacific and to the N Atlantic and Greenland temperature variability (Caissie et al, 2010;Max et al, 2012;Seki et al, 2002). These studies suggest a close linkage to deglacial variations in AMOC associated with rapid atmospheric teleconnection, which were responsible for a quasi-synchronous SST pattern between the N Atlantic and N Pacific during the last deglaciation.…”

Early human use of anadromous salmon in North America at 11,500 y ago

“…Although suitable salmon habitat was likely available in this region throughout the Late Pleistocene, during intervals within glacial periods habitat was probably suboptimal, and especially so near coastal areas surrounding the Bering Sea and the northern Gulf of Alaska (41,42). Recent paleoceanographic data show that conditions improved dramatically between ∼17,000 and 13,000 cal B.P., depending on indicator and location, in terms of warming sea-surface temperatures, reduced cover of seasonal sea ice, and increased primary productivity (41,42). River migration access and spawning habitat in the lower Yukon River basin during the Late Pleistocene was probably not an impediment to salmon, as it was not glaciated, even at maximum glacial extent (38,43).…”