Hopwood Mark J.

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Last Name
Hopwood
First Name
Mark J.
ORCID
0000-0002-9743-079X

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  • Article
    Characteristic depths, fluxes and timescales for Greenland’s tidewater glacier fjords from subglacial discharge‐driven upwelling during summer
    (American Geophysical Union, 2022-03-02) Slater, Donald A. ; Carroll, Dustin ; Oliver, Hilde ; Hopwood, Mark J. ; Straneo, Fiamma ; Wood, Michael ; Willis, Joshua K. ; Morlighem, Mathieu
    Greenland's glacial fjords are a key bottleneck in the earth system, regulating exchange of heat, freshwater and nutrients between the ice sheet and ocean and hosting societally important fisheries. We combine recent bathymetric, atmospheric, and oceanographic data with a buoyant plume model to show that summer subglacial discharge from 136 tidewater glaciers, amounting to 0.02 Sv of freshwater, drives 0.6–1.6 Sv of upwelling. Bathymetric analysis suggests that this is sufficient to renew most major fjords within a single summer, and that these fjords provide a path to the continental shelf that is deeper than 200 m for two-thirds of the glaciers. Our study provides a first pan-Greenland inventory of tidewater glacier fjords and quantifies regional and ice sheet-wide upwelling fluxes. This analysis provides important context for site-specific studies and is a step toward implementing fjord-scale heat, freshwater and nutrient fluxes in large-scale ice sheet and climate models.
  • Article
    Greenland Subglacial Discharge as a driver of hotspots of increasing coastal chlorophyll since the early 2000s
    (American Geophysical Union, 2023-05-18) Oliver, Hilde ; Slater, Donald ; Carroll, Dustin ; Wood, Michael ; Morlighem, Mathieu ; Hopwood, Mark J.
    Subglacial discharge emerging from the base of Greenland's marine‐terminating glaciers drives upwelling of nutrient‐rich bottom waters to the euphotic zone, which can fuel nitrate‐limited phytoplankton growth. Here, we use buoyant plume theory to quantify this subglacial discharge‐driven nutrient supply on a pan‐Greenland scale. The modeled nitrate fluxes were concentrated in a few critical systems, with half of the total modeled nitrate flux anomaly occurring at just 14% of marine‐terminating glaciers. Increasing subglacial discharge fluxes results in elevated nitrate fluxes, with the largest flux occurring at Jakobshavn Isbræ in Disko Bay, where subglacial discharge is largest. Subglacial discharge and nitrate flux anomaly also account for significant temporal variability in summer satellite chlorophyll a (Chl) within 50 km of Greenland's coast, particularly in some regions in central west and northwest Greenland.Runoff and modeled nitrate upwelling can explain temporal variability in surface cholorophyll in some coastal areas in west Greenland