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

Abstract

A marine sediment record from the central Bering Sea, spanning the last 20 thousand years (ka), was studied to unravel the depositional history with regard to terrigenous sediment supply and biogenic sedimentation. Methodic approaches comprised the inference of accumulation rates of siliciclastic and biogenic components, grain-size analysis, and (clay) mineralogy, as well as paleoclimatic modelling. Changes in the depositional history provides insight into land-ocean linkages of paleoenvironmental changes. During the finale of the Last Glacial Maximum, the depositional environment was characterized by hemipelagic background sedimentation. A marked change in the terrigenous sediment provenance during the late Heinrich 1 Stadial (15.7–14.5 ka), indicated by increases in kaolinite and a high glaciofluvial influx of clay, gives evidence of the deglaciation of the Brooks Range in the hinterland of Alaska. This meltwater pulse also stimulated the postglacial onset of biological productivity. Glacial melt implies regional climate warming during a time of widespread cooling on the northern hemisphere. Our simulation experiment with a coupled climate model suggests atmospheric teleconnections to the North Atlantic, with impacts on the dynamics of the Aleutian Low system that gave rise to warmer winters and an early onset of spring during that time. The late deglacial period between 14.5 and 11.0 ka was characterized by enhanced fluvial runoff and biological productivity in the course of climate amelioration, sea-level rise, seasonal sea-ice retreat, and permafrost thaw in the hinterland. The latter processes temporarily stalled during the Younger Dryas stadial (12.9-11.7 ka) and commenced again during the Preboreal (earliest Holocene), after 11.7 ka. High river runoff might have fertilized the Bering Sea and contributed to enhanced upper ocean stratification. Since 11.0 ka, advanced transgression has shifted the coast line and fluvial influence of the Yukon River away from the study site. The opening of the Bering Strait strengthened contour currents along the continental slope, leaving behind winnowed sand-rich sediments through the early to mid-Holocene, with non-deposition occurring since about 6.0 ka.

Deglacial records of terrigenous organic matter accumulation off the Yukon and Amur rivers based on lignin phenols and long-chain n-alkanes

“…2). Wang et al (2021) found that the Alaskan mountain glaciers and Laurentide and Cordilleran ice sheets reached their maximum extent from 20 to 16.5 ka, suggesting permafrost of the Yukon basin may not have begun to be remobilized during this time. The Yukon River discharge did not increase until 16.5 ka (Wang et al, 2021), and the terrigenous OM transported by surface runoff thus may not have increased at ∼ 17.5 ka.…”

“…Wang et al (2021) found that the Alaskan mountain glaciers and Laurentide and Cordilleran ice sheets reached their maximum extent from 20 to 16.5 ka, suggesting permafrost of the Yukon basin may not have begun to be remobilized during this time. The Yukon River discharge did not increase until 16.5 ka (Wang et al, 2021), and the terrigenous OM transported by surface runoff thus may not have increased at ∼ 17.5 ka. Keskitalo et al (2017) found that the OM flux accumulated on the East Siberian Shelf during the PB-Holocene transition was high, and this OM was characterized by high S/V (0.28-0.90; mean value is 0.50) and C/V values (0.19-0.60; mean value is 0.35) (Fig.…”

“…The Yukon basin was mostly unglaciated during the LGM but had permafrost (Schirrmeister et al, 2013). Although some permafrost in the Yukon basin thawed during the last deglaciation (Meyer et al, 2019;Wang et al, 2021), most of the basin is still covered by permafrost today (Fig. 1).…”

“…2), which coincides with the beginning retreat of Alaskan glaciers (Dyke, 2004). The glacial meltwaters drained through the Yukon River and enhanced fluvial discharge to the Bering Sea (Wang et al, 2021). The ICD in Alaska and Beringia might have started to be remobilized at ∼ 16.5 ka (Meyer et al, 2019;Wang et al, 2021), subsequently enhancing the MAR of ICDderived OM off the Bering Shelf.…”

Beringia and the peopling of the Western Hemisphere

“…Driftwood derived from a source (pine, alder) in the southern NW Pacific may have been available after 16 ka [96]. Perhaps cold HE 1, which began approximately 17 ka, was a catalyst for a shift to a marine diet at a time when terrestrial resources would have declined, while accelerated glacial run-off from eastern Beringia is thought to have fertilized waters on the southern coast [97].…”