Local and regional controls on Holocene sea ice dynamics and oceanography in Nares Strait, Northwest Greenland

Abstract

Nares Strait is one of three channels that connect the Arctic Ocean to Baffin Bay. Unique sea-ice conditions in the strait lead to the formation of landfast ice arches at its northern and southern ends. These ice arches regulate Arctic sea-ice and freshwater export through the strait and promote the opening of the North Water polynya. The present study addresses the paucity of pre-satellite records of environmental conditions in the Nares Strait area, and aims at reconstructing Holocene sea-ice conditions and ocean circulation in the strait. The investigation is based on a marine sediment core strategically retrieved from under the current ice arch in Kane Basin to the south of Nares Strait, and provides a continuous record spanning the past ca 9 kyrs. We use benthic foraminiferal assemblages and sea-ice biomarkers to infer changes in Holocene ocean circulation and sea-ice conditions in Kane Basin. The establishment of the modern ocean circulation in Kane Basin is related to ice sheet retreat and postglacial rebound, while changes in sea-ice cover concur with major shifts in the Arctic Oscillation (AO). Our results suggest that sea-ice cover in Kane Basin was highly variable between ca 9.0 and 8.3 cal. ka BP, before increasing, probably in link with the 8.2 cold event and the opening of Nares Strait. A short period of minimum sea-ice cover and maximum Atlantic bottom water influence occurred between ca 8.1 and 7.5 cal. ka BP, when Kane Basin was deeper than for the remaining of the Holocene. As atmospheric temperatures dropped, sea-ice cover intensified in Kane Basin between ca 7.5 and 5.5 cal. ka BP, but strong winds under prevailing positive-like AO conditions likely prevented the formation of ice arches in Nares Strait. During this time, our micropaleontological data show that Atlantic water was progressively excluded from Kane Basin by the postglacial isostatic rebound. Increasingly cooler atmospheric temperatures and a shift towards more negative phases of the AO may have promoted the establishment of ice arches in Nares Strait between ca 5.5 and 3.0 cal. ka BP. Instabilities in the Kane Basin ice arch ca 3.0 cal. ka BP coincide with a shift towards prevailing positive phases of the AO, while a brief recovery of the ice arch occurred during more negative-like AO conditions between ca 1.2 and 0.2 cal. ka BP.

Quantifying Provenance and Transport Pathways of Holocene Sediments From the Northwestern Greenland Margin

“…Overall, our mineralogical and geochemical data suggest that the period after 5.8 cal ka BP likely corresponds to the progressive establishment of the modern sedimentation in this region but reflect minimal changes consistent with the neoglaciation in our marine record. Nevertheless, Late Holocene changes in Kane Basin were observed in the same sediment sequence (core Kane2B) based on micropaleontological proxies (Caron, Rochon, et al, 2019; Georgiadis et al, ).…”

“…Furthermore, Jennings et al (2019) reported relatively high sedimentation rates and deposition of detrital carbonate until 7.2 cal ka BP, while ice margin retreated, in agreement with our results. Besides, Georgiadis et al () noticed an expanding sea‐ice cover in Kane basin between ~7.5 and 5.5 cal ka BP, which remained important afterward. This extended sea‐ice cover associated to the enhanced southward flow could have triggered an increased detrital sediment input by sea‐ice transport, originating from the north.…”

“…Cores AMD14‐204 and AMD14‐210 (hereinafter referred to as 204 and 210) are located on the northwest Greenland margin, in the cross‐shelf troughs west of Upernavik Isstrøm, and in Melville Bay, respectively, whereas core AMD14‐Kane2B (hereinafter referred to as Kane2B) is located in the Kane Basin (Figure and Table ). Core Kane2B age model was calibrated using a regional reservoir correction of Δ R = 240 ± 51 (Georgiadis et al, , ), while age models for cores 204 and 210 were calibrated using a regional age reservoir correction of Δ R = 140 ± 30 (Caron, St‐Onge, et al, 2019). These Δ R values were selected based on previous regional studies (Jackson et al, ; Jennings et al, ; Lloyd et al, ; Moros et al, ), and age models were validated with palaeomagnetic data (Caron, St‐Onge, et al, 2019).…”

“…An improved version of core 204 age model was established with the addition of organic matter dating (J. Giraudeau, personal communication, December 2019). The chronostratigraphic framework, sedimentation rates, CT scan images, and sedimentary units of the three cores are presented in Figure S1 in the supporting information (Caron, St‐Onge, et al, 2019; Georgiadis et al, , ).…”

Learning from the past: Impact of the Arctic Oscillation on sea ice and marine productivity off northwest Greenland over the last 9,000 years

“…This could partly explain the presence of sub-ice colonial species such as M. arctica that have developed strategies to mitigate the effect of unfavorable sea-ice microstructure (Krembs et al, 2011). To the north, evidence of instabilities in the Kane Basin ice arch (Georgiadis et al, 2020) at our study site (Caron et al, 2020), and is coherent with the retreat of the Qangattaq ice cap on the Nuussuaq peninsula between c. 2.5 and 1.9 kyr BP (Schweinsberg et al, 2017) and the Greenland ice-sheet margin in Northern Nunatarssuaq between 2.1 and 1.6 kyr BP (Farnsworth et al, 2018), at the transition to a period of significant boreal atmospheric warming that is commonly referred to as the Roman Warm Period (~2.0-1.65 kyr BP, Wanner et al, 2008).…”