EGU2020-12976
https://doi.org/10.5194/egusphere-egu2020-12976
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Depth and properties of freshwater export from the Greenland Ice Sheet modulated by ice-ocean processes

Donald Slater and Fiamma Straneo
Donald Slater and Fiamma Straneo
  • Scripps Institution of Oceanography, United States of America (daslater@ucsd.edu)

Freshwater export from the Greenland Ice Sheet to the surrounding ocean has increased by 50% since the early 1990s, and may triple over the coming century under high greenhouse gas emissions. This increasing freshwater has the potential to influence both the regional and large-scale ocean, including marine ecosystems. Yet quantification of these impacts remains uncertain in part due to poor characterization of freshwater export, and in particular the transformation of freshwater around the ice sheet margin by ice-ocean processes, such as submarine melting, plumes and fjord circulation. Here, we combine in-situ observations, ocean reanalyses and simple models for ice-ocean processes to estimate the depth and properties of freshwater export around the full Greenland ice sheet from 1991 to present. The results show significant regional variability driven primarily by the depth at which freshwater runoff leaves the ice sheet. Areas with deeply-grounded marine-terminating glaciers are likely to export freshwater to the ocean as a dilute mixture of freshwater and externally-sourced deep water masses, while freshwater from areas with many land-terminating glaciers is exported as a more concentrated mixture of freshwater and near-surface waters. A handful of large glacier-fjord systems dominate ice sheet freshwater export, and the vast majority of freshwater export occurs subsurface. Our results provide an ice sheet-wide first-order characterization of how ice-ocean processes modulate Greenland freshwater export, and are an important step towards accurate representation of Greenland freshwater in large-scale ocean models.

How to cite: Slater, D. and Straneo, F.: Depth and properties of freshwater export from the Greenland Ice Sheet modulated by ice-ocean processes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12976, https://doi.org/10.5194/egusphere-egu2020-12976, 2020

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Display material version 1 – uploaded on 04 May 2020
  • CC1: Comment on EGU2020-12976, Francisco Navarro, 08 May 2020

    Hi again, Donald.

    Having answered to my question (is the ratio of freshwater entering fjords at grounding to upwelled & exported diluted freshwater fairly similar at different locations, or have you found significant differences at regional/local scales?) in terms of the main controls for the ratio, the "continuation question" would be whether you have observed any regional differences in the ratio, i.e. whether the controls mentioned in your answer, together with a possible regional prevalence of any of them, could imply that that ratio be larger in some regions compared to others (in case you have made such kind of analysis).

    Thanks.

     

    • AC1: Reply to CC1, Donald Slater, 08 May 2020

      Hi Paco, thank you for the question!

      Below I have uploaded a plot of the pure freshwater content in the glacially modified water after upwelling in the plume (sorry for the poor quality - the system would not let me upload a higher resolution). I do not really see obvious regional patterns. There are some glaciers that stick out - e.g. Humboldt glacier in NW Greenland has a high freshwater content at neutral buoyancy in the plume because it has a shallow grounding line and a high subglacial discharge. And the same may be the case for KNS in the SW. Otherwise the freshwater content is relatively similar everywhere. Hope that helps.

      Donald

      • CC2: Reply to AC1, Francisco Navarro, 08 May 2020

        Thanks, Donald. Yes, there is no regional pattern.

        It was mostly curiosity.

        Have a nice weekend.