Abstract
Abstract. The mass of the Greenland ice sheet is declining as mass gain from snow accumulation is exceeded by mass loss from surface meltwater runoff, marine-terminating glacier calving and submarine melting, and basal melting. Here we use the input–output (IO) method to estimate mass change from 1840 through next week. Surface mass balance (SMB) gains and losses come from a semi-empirical SMB model from 1840 through 1985 and three regional climate models (RCMs; HIRHAM/HARMONIE, Modèle Atmosphérique Régional – MAR, and RACMO – Regional Atmospheric Climate MOdel) from 1986 through next week. Additional non-SMB losses come from a marine-terminating glacier ice discharge product and a basal mass balance model. From these products we provide an annual estimate of Greenland ice sheet mass balance from 1840 through 1985 and a daily estimate at sector and region scale from 1986 through next week. This product updates daily and is the first IO product to include the basal mass balance which is a source of an additional ∼24 Gt yr−1 of mass loss. Our results demonstrate an accelerating ice-sheet-scale mass loss and general agreement (coefficient of determination, r2, ranges from 0.62 to 0.94) among six other products, including gravitational, volume, and other IO mass balance estimates. Results from this study are available at https://doi.org/10.22008/FK2/OHI23Z (Mankoff et al., 2021).
Highlights
Over the past several decades, mass loss from the Greenland ice sheet has increased (Khan et al, 2015; IMBIE Team, 2019)
5.1 Surface mass balance In This Study we generate an output based on each of the three regional climate models (RCMs) (HIRHAM/HARMONIE, Modèle Atmosphérique Régional (MAR), and Regional Atmospheric Climate MOdel (RACMO)); in addition to these we generate a final and fourth SMB field defined as a combination of (1) the adjusted reconstructed SMB from 1840 through 1985 (Sect. 5.4) and (2) the average of HIRHAM/HARMONIE, MAR, and RACMO from 1986 through a few months ago, the average of HIRHAM/HARMONIE and MAR from a few months ago through yesterday, and MAR from yesterday through week
This study is the first to provide a data set containing more than a century and real-time estimates detailing the state of Greenland ice sheet mass balance, with regional or sector spatial and daily temporal resolution products of surface mass balance, discharge, basal mass balance, and the total mass balance
Summary
Over the past several decades, mass loss from the Greenland ice sheet has increased (Khan et al, 2015; IMBIE Team, 2019). Different processes dominate the regional mass loss of the ice sheet, and their relative contribution has fluctuated in time (Mouginot and Rignot, 2019). In the 1970s most sectors gained mass due to positive surface mass balance (SMB), except the northwestern sector, where discharge losses dominated. In the 2010s, all sectors lost mass, with some sectors losing mass almost entirely via negative SMB and others primarily due to discharge (Fig. 1). There are three common methods for estimating mass balance – changes in gravity (Barletta et al, 2013; Groh et al, 2019; IMBIE Team, 2019; Velicogna et al, 2020), changes in volume Mankoff et al.: Greenland mass balance 1840 through week
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