Preprints
https://doi.org/10.5194/tc-2020-276
https://doi.org/10.5194/tc-2020-276
28 Oct 2020
 | 28 Oct 2020
Status: this discussion paper is a preprint. It has been under review for the journal The Cryosphere (TC). The manuscript was not accepted for further review after discussion.

Significant water vapor fluxes from the Greenland Ice Sheet detected through water vapor isotopic (δ18O, δD, deuterium excess) measurements

Ben G. Kopec, Pete D. Akers, Eric S. Klein, and Jeffery M. Welker

Abstract. The summer of 2019 was marked by an extensive early onset of surface melt and record volume losses of the Greenland Ice Sheet (GrIS), which is part of a larger trend of increasing melt over time. Given the growing spatial extent of melt, the flux of water vapor from the ice to the atmosphere is becoming an increasingly important component of the GrIS mass balance that merits investigation and quantification. We examine the isotopic composition of water vapor from Thule Air Base, NW Greenland, particularly the deuterium excess (d-excess), to quantify the magnitude of GrIS vapor fluxes. To do this, we observe only water vapor transported off the ice sheet (i.e., when easterly winds occur) and during the active melt season. We find that the GrIS-derived water vapor d-excess values are controlled by two main factors: 1) the d-excess of the sublimating vapor, which is determined, in part, by the relative humidity and wind speed above the ice sheet, and 2) the proportion of sublimation- vs. marine-sourced moisture. Here, the GrIS melt extent serves as a proxy for the sublimation source and the North Atlantic Oscillation provides a measure of the meridional transport of marine moisture. We demonstrate that sublimation contributes ~20 % of the water vapor transported from the GrIS during the melt season. Sublimation is thus an important component of GrIS mass balance and the regional hydrologic cycle, and this flux will become more important in the coming years as further warming continues GrIS negative mass balance trends.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Ben G. Kopec, Pete D. Akers, Eric S. Klein, and Jeffery M. Welker
 
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Ben G. Kopec, Pete D. Akers, Eric S. Klein, and Jeffery M. Welker

Data sets

Thule, Greenland, 10 minute water vapor isotopes (δ18O, δD, d-excess), August 2017 - August 2019 Pete D. Akers, Jeffrey M. Welker, and Ben G. Kopec https://doi.org/10.18739/A21J9779S

PROMICE automatic weather station data Geological Survey of Denmark and Greenland https://doi.org/10.22008/promice/data/aws

MEaSUREs Greenland Surface Melt Daily 25km EASE-Grid 2.0, Version 1 Thomas Mote https://doi.org/10.5067/MEASURES/CRYOSPHERE/nsidc-0533.001

Ben G. Kopec, Pete D. Akers, Eric S. Klein, and Jeffery M. Welker

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Short summary
Significant mass loss to the Greenland Ice Sheet has occurred over recent decades, marked by a record summer melt season in 2019. Water vapor fluxes from the ice sheet surface, including sublimation and meltwater evaporation, are a growing component of the mass balance. Using water vapor isotope measurements in northwest Greenland, we identify the signal of these fluxes and show how they correspond with melt extent. These vapor fluxes contribute ~20 % of water vapor advected off the ice sheet.