Intra- and inter-annual variability in dynamic discharge from the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, and its role in modulating mass balance

Pablo Sánchez-Gámez,Toby J Benham,Andrey F Glazovsky,Francisco J Navarro,Julian A Dowdeswell,Robin P Bassford

doi:10.1017/jog.2019.58

Abstract

AbstractWe determined ice velocities for the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, during November 2016–November 2017, by feature-tracking 54 pairs of Sentinel-1 synthetic-aperture radar images. Seasonal velocity variations with amplitudes up to 10% of the yearly-averaged velocity were observed. Shorter-term (<15 d) intra-annual velocity variations had average and maximum deviations from the annual mean of up to 16 and 32%, respectively. This indicates the errors that could be incurred if ice discharge values determined from a single pair of images were extrapolated to the whole year. Average ice discharge for 2016–2017 was 1.93 ± 0.12 Gt a−1. The difference from an estimate of ~ 1.4 Gt a−1for 2003–2009 was attributed to the initiation of ice stream flow in Basin BC. The total geodetic mass balance over 2012–2016 was − 1.72 ± 0.67 Gt a−1(− 0.31 ± 0.12 m w.e. a−1). The climatic mass balance was not significantly different from zero, at 0.21 ± 0.68 Gt a−1(0.04 ± 0.12 m w.e. a−1), and has remained near zero at decadal-scale for the last four decades. Therefore, the total mass balance has been controlled largely by variations in ice discharge, whose long-term changes do not appear to have responded to environmental changes but to the intrinsic characteristics of the ice cap governing tidewater glacier dynamics.

Highlights

Calving is an important mechanism of mass loss for marine-terminating Arctic glaciers, including those of the Russian Arctic (Moholdt and others, 2012a; Melkonian and others, 2016)
To determine the processes that might drive the observed shortterm ice velocity variations (Fig. 3), and in particular whether they respond to an external forcing with a spatial scale large enough to affect all basins, or are driven by local dynamic conditions which can differ among basins, it is of interest to analyse whether the changes observed in the various basins are correlated
The following main conclusions are drawn from our analysis: (1) During the period November 2016–November 2017, the marine-terminating margins of the Academy of Sciences Ice Cap remained nearly stable, so that ice discharge and calving flux are equivalent in our study, at 1.93 ± 0.12 Gt a−1

Summary

Introduction

Calving is an important mechanism of mass loss for marine-terminating Arctic glaciers, including those of the Russian Arctic (Moholdt and others, 2012a; Melkonian and others, 2016). In spite of recent climate warming over the Arctic region (Hartmann and others, 2013), the recent ice-mass losses from the Russian Arctic were moderate, totalling ∼ 11 ± 4 Gt a−1 over 2003–2009 (Moholdt and others, 2012b; Matsuo and Heki, 2013; Gardner and others, 2013). This is far less than other Arctic regions such as the Canadian Arctic, Greenland peripheral glaciers and glaciers of Alaska, even if considered per unit area (Gardner and others, 2013). The mass losses from the Russian Arctic by the end of the 21st century have been projected to increase substantially (Radić and others, 2013), with an expected contribution to sea-level rise of between 9.5 ± 4.6 and 18.1 ± 5.5 mm in sea-level equivalent over 2010–2100, depending on emissionpathway scenarios (Huss and Hock, 2015)

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Discussion

Conclusion