Contribution of Icelandic ice caps to sea level rise: Trends and variability since the Little Ice Age

Abstract

In total, Icelandic ice caps contain ∼3600 km3 of ice, which if melted would raise sea level by ∼1 cm. Here, we present an overview of mass changes of Icelandic ice masses since the end of the 19th century. They have both gained and lost mass during this period. Changes in ice volume have been estimated both through surface mass balance measurements (performed annually since ∼1990) and differencing of digital elevation models derived from various satellite and airborne observations. While the glaciers showed little mass loss as the 20th century began, losses increased rapidly after 1925, peaked in the 1930s and 1940s, and remained significant until the 1960s. After being near‐zero or even positive during the 1980s and early 1990s, glacier mass budgets declined considerably, and have since the mid‐1990s shown an average annual loss of 9.5±1.5 Gt a−1, contributing ∼0.03 mm a−1 to sea level rise. Since 1995 interannual variability in mass loss is high, ranging from 2.7 to 25.3±1.5 Gt a−1, corresponding to surface mass balances of −0.2 to −2.2 ± 0.15 m we a−1. This variability is driven by climate fluctuations and also by transient reduction of albedo due to volcanic eruptions.

Changes in the southeast Vatnajökull ice cap, Iceland, between ~ 1890 and 2010

“…The ice divides were determined from the lidar DEM and the data base of the GGIES. Even though there have been surges in the larger outlets of Vatnajökull (Björnsson et al, 2003), they have not affected the ice divides of the studied southeast outlet glaciers during the study period. Uplift rates around Vatnajökull in the last 20 years have been on the order of 10-30 mm a −1 , highest around the edge of the ice cap (Árnadóttir et al, 2009;Auriac et al, 2013).…”

“…a −1 (apart from Heinabergsjökull) during the time period 2002-2010 is similar to the measured specific mass balance on the larger ice caps in Iceland in the first decade of the 21st century, equal to −1.0 ± 0.5 m w.e. a −1 Björnsson et al, 2013;Jóhannesson et al, 2013). The warming in Iceland since the 1990s has been 3-4 times higher than the average warming of the Northern Hemisphere during the same time interval (Jones et al, 2012;Björnsson et al, 2013), which may explain the high rates of mass loss in the first decade of the 21st century.…”

“…The warming in Iceland since the 1990s has been 3-4 times higher than the average warming of the Northern Hemisphere during the same time interval (Jones et al, 2012;Björnsson et al, 2013), which may explain the high rates of mass loss in the first decade of the 21st century. In situ mass balance measurements of glaciers in Iceland and degree-day mass balance models of selected glaciers indicate that the mass balance is governed by variation in summer ablation (which is strongly correlated with temperature), rather than winter accumulation (Björnsson and Pálsson, 2008 , 2009Pálsson et al, 2012;Björnsson et al, 2013).…”

“…After 1995, warmer temperatures than in the preceding 2-3 decades (Fig. 2b) caused retreat of the southeast outlets, which increased after the year 2000 (Björnsson and Pálsson, 2008;Björnsson et al, 2013).…”

“…Björnsson and Pálsson, 2008;Guðmundsson et al, 2009Guðmundsson et al, , 2011Pálsson et al, 2012). In situ measurements show that mass balance was positive on Vatnajökull 1991-1994, but negative since then (Björnsson and Pálsson, 2008;Björnsson et al, 2013). 39.5 ± 0.9 38.9 ± 0.7 (98 %) 36.1 ± 0.5 (91 %) 35.5 ± 0.5 (90 %) 34.8 ± 0.3 (88 %) 33.2 ± 0.1 (84 %) Kotárj.…”