Land Ice Freshwater Budget of the Arctic and North Atlantic Oceans: 1. Data, Methods, and Results

Abstract

The freshwater budget of the Arctic and sub‐polar North Atlantic Oceans has been changing due, primarily, to increased river runoff, declining sea ice and enhanced melting of Arctic land ice. Since the mid‐1990s this latter component has experienced a pronounced increase. We use a combination of satellite observations of glacier flow speed and regional climate modeling to reconstruct the land ice freshwater flux from the Greenland ice sheet and Arctic glaciers and ice caps for the period 1958–2016. The cumulative freshwater flux anomaly exceeded 6,300 ± 316 km 3 by 2016. This is roughly twice the estimate of a previous analysis that did not include glaciers and ice caps outside of Greenland and which extended only to 2010. From 2010 onward, the total freshwater flux is about 1,300 km 3 /yr, equivalent to 0.04 Sv, which is roughly 40% of the estimated total runoff to the Arctic for the same time period. Not all of this flux will reach areas of deep convection or Arctic and Sub‐Arctic seas. We note, however, that the largest freshwater flux anomalies, grouped by ocean basin, are located in Baffin Bay and Davis Strait. The land ice freshwater flux displays a strong seasonal cycle with summer time values typically around five times larger than the annual mean. This will be important for understanding the impact of these fluxes on fjord circulation, stratification, and the biogeochemistry of, and nutrient delivery to, coastal waters.

Role of Greenland Freshwater Anomaly in the Recent Freshening of the Subpolar North Atlantic

“…Locations and discharge rates of the Greenland freshwater sources (Figures a and ) are derived from gridded products described and analyzed in detail by Bamber et al (, ). The data set of Bamber et al () is a gridded product (5 × 5‐km grid) with realistic geographic distribution and temporal variability that provides monthly land ice freshwater flux from the Greenland ice sheet.…”

“…The data set of Bamber et al () is a gridded product (5 × 5‐km grid) with realistic geographic distribution and temporal variability that provides monthly land ice freshwater flux from the Greenland ice sheet. The updated version (Bamber et al, ) also includes freshwater flux from the Arctic glaciers. The Greenland freshwater flux for the model experiments is obtained from the first data set of Bamber et al () until 2010 and from the second data set of Bamber et al () for 2011–2016.…”

“…The updated version (Bamber et al, ) also includes freshwater flux from the Arctic glaciers. The Greenland freshwater flux for the model experiments is obtained from the first data set of Bamber et al () until 2010 and from the second data set of Bamber et al () for 2011–2016.…”

“…(a) Map of the study region. The isobaths are drawn every 500 m. Colored points along the coast of Greenland show freshwater fluxes (km 3 /month) of the individual freshwater sources in the model forcing field for July 2015 derived from Bamber et al (). The passive tracer is imposed at every location and prescribed tracer flux is proportional to the freshwater flux anomaly.…”

Accelerated Volume Loss in Glacier Ablation Zones of NE Greenland, Little Ice Age to Present

“…Thomas et al (2006) estimated that total GrIS loss had more than doubled from 4 to 50 Gt/year between 1993/1994and 1998/1999to 57 to 105 Gt/year between 1998/1999and 2004. Bamber et al (2018, their The lack of a spatial pattern that we evidence in individual glacier changes (Figure 3c) is surprising. Bamber et al (2018, their The lack of a spatial pattern that we evidence in individual glacier changes (Figure 3c) is surprising.…”