Oceanographic and Climatic Change in the Bering Sea, Last Glacial Maximum to Holocene

Abstract

Post‐glacial sea level rise led to a direct connection between the Arctic and Pacific Oceans via the Bering Strait. Consequently, the Bering Sea experienced changes in connectivity, size, and sediment sources that were among the most drastic of any ocean basin in the past 30,000 years. However, the sedimentary response to the interplay between climate change and sea level rise in high‐latitude settings such as Beringia remains poorly resolved. To ascertain changes in sediment delivery, productivity, and regional oceanography from the Last Glacial Maximum (LGM) to the Holocene, we analyzed sedimentological, geochemical, and isotopic characteristics of three sediment cores from the Bering Sea. Interpretations of productivity, terrestrial input, nutrient utilization, and circulation are based on organic carbon isotopes (δ13Corg), total organic carbon (TOC), bulk nitrogen isotopes, total organic nitrogen, carbon/nitrogen ratios, elemental X‐ray fluorescence data, grain size, and presence of laminated or dysoxic, green intervals. Principal component analysis of these data captures key climatic intervals. The LGM was characterized by low productivity across the region. In the Bering Sea, deglaciation began around 18–17 ka, with increasing terrestrial sediment and TOC input. Marine productivity increased during the Bølling‐Allerød when laminated sediments revealed dysoxic bottom waters where denitrification was extreme. The Younger Dryas manifested increased terrestrial input and decreased productivity, in contrast with the Pre‐Boreal, when productivity markedly rebounded. The Pre‐Boreal and Bølling‐Allerød were similarly productive, but changes in the source of TOC and a δ13Corg depletion suggest the influence of a gradually flooding Bering Shelf during the Pre‐Boreal and Holocene.

Deglacial Land-Ocean Linkages at the Alaskan Continental Margin in the Bering Sea

“…The lithostratigraphy of the sediment record from site SO202-18 confirms descriptions, datings, and compositional data from other sediment records along the Bering Slope (Sancetta et al, 1984;Cook et al, 2005;Pelto et al, 2018). In the following section, we will consider modes of sedimentary processes and terrigenous sediment provenance at site SO202-18 on the Alaskan continental margin of the Bering Sea.…”

“…As for the other end members, according to information from literature, several ways of interpretation of EM1 are possible. Such clay-rich sediments were also recognized in other sediment records from the Bering Slope for the same time (Pelto et al, 2018). In modern sediments, this grain-size population cannot be found in the Bering Sea (Wang et al, 2016).…”

“…As a focal area in the Meridional Overturning Circulation (MOC), the North Atlantic region since long has been identified as an important actor in the global climate system (Broecker et al, 1985;Clement and Peterson, 2008;Ziemen et al, 2019). During the last decades, increasing attention has been given to the paleooceanography of the North Pacific and its marginal seas, where interacting dynamic processes of water-mass formation, ocean stratification, sea-level fluctuations, biological productivity, seaice formation, and fresh-water pulses show global connections as integral part of the global MOC and via atmospheric teleconnections (Cook et al, 2005;Diekmann et al, 2008;Takahashi et al, 2011;Gersonde, 2012;Max et al, 2014;Pelto et al, 2018;Lohmann et al, 2019;Davis et al, 2020;Praetorius et al, 2020).…”

A simulated Northern Hemisphere terrestrial climate dataset for the past 60,000 years

“…This period encapsulated the last glacial maximum (LGM), when temperatures were potentially between 19–22 °C cooler across Greenland 1 , resulting in expansion of ice cover and consequent polar amplification 2 . This lowered sea level by up to 127–135 m 3 , impacted ocean circulation 4 and opened previously inundated land bridges such as the Bering Straits 5 , potentially influencing the migration of animal species including humans 6 . Prior to the LGM, the climate was cold but was punctuated with a high degree of millennial variability.…”

Sea surface temperature across the Subarctic North Pacific and marginal seas through the past 20,000 years: A paleoceanographic synthesis

“…3), with western sites generally cooler than those along Bowers Ridge or the Umnak Plateau. The complexity of the deglaciation may be derived from the physical reorganization of the basin associated with the reopening of the Bering Strait, inundation of the shallow shelf, loss of sea ice, and a redirection of Alaskan rivers into the Bering Sea (Sancetta, 1983;Caissie et al, 2010;Pelto et al, 2018). During the deglaciation, several records from across the Bering Sea (HYL02-02-17JPC, SO201-2-85 KL and HYL02-02-51JPC) indicate a cool early Bølling-Allerød, followed by warming.…”