Abstract
AbstractDuring the past four decades significant decrease in Arctic sea ice and a dramatic ice mass loss of the Greenland Ice Sheet (GIS) has been coincident with global warming and an increase in atmospheric CO2. In Northeast Greenland significant mass loss from the outlet glaciers Nioghalvfjerdsbræ (79NG) and Zachariæ Isstrøm (ZI) and intensive seasonal breakup of the local Norske Øer Ice Barrier (NØIB) have also been observed since 2000. In order to better understand the processes driving these modern changes, studies of paleoclimate records are important and of major societal relevance. A multiproxy study including organic‐biogeochemical and micropaleontological proxies was carried out on a marine sediment core recovered directly in front of 79NG. Data from Core PS100/270 evidenced a strong inflow of warm recirculating Atlantic Water across the Northeast Greenland shelf from the early Holocene between ~10 and 7.5 ka. An overall high in phytoplankton productivity occurred within a stable sea ice margin regime, accompanied by 79NG retreat most probably triggered by peak solar insolation and changes in the local ocean circulation. Enhanced basal melt of the underside of 79NG at ~7.5 ka then led to the total disintegration of the ice shelf. The released freshwater would have driven water column stratification and promoted the formation of the local landfast ice barrier, which is shown by lowered biomarker values and foraminifera abundances toward the end of the early Holocene. Near perennial sea ice conditions with short summers and 79NG retreat to the inner fjord then prevailed from ~7.5 to ~0.8 ka.
Highlights
Introduction and Regional SettingIn the past three decades, anthropogenic climate change has had a rapid and dramatic effect on Arctic sea ice and the Greenland Ice Sheet (Dai et al, 2019; Shepherd et al, 2020)
Recent satellite observations show that Greenland Ice Sheet (GIS) mass loss and the Arctic sea ice loss have doubled since the beginning of this century (Kjeldsen et al, 2015)
This study investigated a core record collected from the seafloor adjacent to the present 79NG shelf (Core PS100/270, Figure 1a), which records a history of proximal/distal glaciomarine and sub‐ice shelf conditions as 79NG grounding line and ice shelf retreated passed this site during the Last Glacial Maximum (LGM) to Holocene recession
Summary
Introduction and Regional SettingIn the past three decades, anthropogenic climate change has had a rapid and dramatic effect on Arctic sea ice and the Greenland Ice Sheet (Dai et al, 2019; Shepherd et al, 2020). The drastic increase of atmospheric CO2 concentrations has led to rising ocean and atmosphere temperatures, which are compounded by Arctic amplification and complex positive feedback loops, for example, albedo feedback (Dai et al, 2019; Day et al, 2012; Kay et al, 2011; Notz & Marotzke, 2012; Thackeray & Hall, 2019) Both are key components of the climate system, while the strong negative shift in mass balance of GIS may cause a global sea‐level rise of up to 0.09 to 0.88 m by the year 2100, causing irreversible damage to the environment and enormous economic impacts on our society (Meredith et al, 2019; Nordhaus, 2019; Stern & Taylor, 2007). Recent satellite observations show that GIS mass loss and the Arctic sea ice loss have doubled since the beginning of this century (Kjeldsen et al, 2015)
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