Atlantic Water warming increases melt below Northeast Greenland’s last floating ice tongue

Abstract

The 79 North Glacier (79NG) features Greenland’s largest floating ice tongue. Even though its extent has not changed significantly in recent years, observations have indicated a major thinning of the ice tongue from below. Both ocean warming and an increase in subglacial discharge from the ice sheet induced by atmospheric warming could increase the basal melt; however, available observations alone cannot tell which of these is the main driver. Here, we employ a global simulation which explicitly resolves the ocean circulation in the cavity with 700 m resolution to disentangle the impact of the ocean and atmosphere. We find that the interannual variability of basal melt below 79NG over the past 50 years is mainly associated with changes in the temperature of the Atlantic Intermediate Water inflow, which can be traced back across the Northeast Greenland continental shelf to the eastern Fram Strait with a lag of 3 years.

The atmosphere-land/ice-ocean system in the region near the 79N Glacier in Northeast Greenland: Synthesis and key findings from GROCE

“…These findings are consistent with results obtained with the global 3D ocean-sea ice model. Sensitivity experiments with reduced and enhanced subglacial discharge confirm the square-root relationship with basal melt (Wekerle et al, 2024). Regarding ocean temperatures, we find that mean basal melt rates follow a quadratic function of AIW inflow temperature in the 3D ocean-sea ice model.…”

“…Our 3D ocean-sea ice model, featuring a horizonatal mesh resolution of 700 m in the cavity and its surrounding, reveals that the warm and salty AIW enters the cavity through its deepest channel as a bottom-intensified gravity current (Wekerle et al, 2024), in agreement with Schaffer et al (2020). The warm AIW then circulates cyclonically around the cavity.…”

“…16), which increase by 1.38 m a −1 per decade. Wekerle et al (2024) conclude that the temporal evolution of Atlantic Water in Fram Strait is the main driver of changes in basal melt rates of the 79NG over the past 50 years. in the ocean surrounding Greenland.…”

“…The 3D ocean simulation also shows that not the AIW temperature on the NE Greenland shelf but also the basal melt rates of the 79NG are strongly connected to the upstream ocean conditions (Fig. 16; Wekerle et al (2024)). Simulated annual mean basal melt rates are significantly correlated with the inflow temperature at the calving front (r=0.85), whereas the correlation with the subglacial discharge across the grounding line is not significant (r=0.22).…”

“…An advantage of the FESOM model family is its multi-resolution capability in a global framework, which allows us to easily adapt the mesh resolution to the area of interest. FESOM2.1 includes an ice-shelf component explicitly resolving the 79NG and ZI cavities (Wekerle et al, 2024). The thermodynamic interaction between ocean and ice shelf (i.e.…”