Search

Tracy and Heilprin, marine-terminating glaciers that drain into the eastern end of Inglefield Gulf in northwest Greenland, exhibit remarkably different behaviors despite being adjacent systems. Losing mass since 1892, Tracy Glacier has dramatically accelerated, thinned, and retreated. Heilprin has retreated only slightly during the last century and has remained almost stationary in the most recent decade. Previous studies suggest that Tracy's base is deeper than Heilprin's at the calving front (over 600 m, as opposed to the 350 m depth at Heilprin), which exposes it to warmer subsurface waters, resulting in more rapid retreat. We investigate the local oceanographic conditions in Inglefield Gulf and their interactions with Tracy and Heilprin using data collected in 2016 and 2017 as part of NASA's Oceans Melting Greenland mission. Based on improved estimates of the fjord geometry and 20 temperature and salinity profiles near the fronts of these two glaciers, we find clear evidence that fjord waters are modified by ocean-ice interactions with Tracy Glacier. We find that Tracy thinned by 9.9 m near its terminus between 2016 and 2017, while Heilprin thinned by only 1.8 m. Using a simple subglacial plume model, we find that Tracy's deeper depth at the front results in a more vigorous entrainment of warm subsurface waters, leading to more rapid melting. Model results support the hypothesis that Tracy's deeper front results in faster glacier retreat, despite the presence of a shallow sill (~300 m) that may prevent the warmest waters from reaching Tracy. [ABSTRACT FROM AUTHOR]

Melting of the Greenland Ice Sheet has the potential to raise sea level by 7.36 m and is already contributing to global sea level rise at a rate higher than 1 mm yr-1. Computer models are our best tools to make projections of the mass balance of Greenland over the next centuries, but these models rely on bed topography data that remain poorly constrained near glacier termini. Accurate bed topography in the vicinity of calving fronts is critical for numerical models, as the shapes of the glacier bed and of the nearby bathymetry control both the ocean circulation in the fjord and the stability and response of the ice sheet to climate warming. NASA's Oceans Melting Greenland (OMG) mission is collecting bathymetry data along Greenland fjords at several glacier termini. Here, we show that these measurements are transforming our knowledge of fjord and glacier depths. Using a mass conservation approach, we combine OMG bathymetry with observations of ice velocity and thickness to produce estimates of bed depth and ice thickness across the ice-ocean boundary with unprecedented accuracy and reliability. Our results along the northwest coast of Greenland reveal complex structural features in bed elevation, such as valleys, ridges, bumps, and hollows. These features have important implications for both channeling ice flow toward the continental margin, and for controlling the amount of warm, salty Atlantic Water that reaches the glaciers. [ABSTRACT FROM AUTHOR]