Abstract
In recent decades, glaciers outside Greenland and Antarctica have shown increasingly rapid rates of mass loss and retreat of the ice front, which is associated with climatic and oceanic warming. Due to their maritime location, Icelandic glaciers are sensitive to short-term climate fluctuations and have shown rapid rates of retreat and mass loss over the last decade. In this study, historical maps (1941–1949) of the US Army Map Service (AMS series C762) and optical satellite imagery (Landsat 1, Landsat 5, Landsat 7, Landsat 8, and Sentinel-2) are used to study the Langjökull, Hofsjökull and Vatnajökull ice caps. By the help of the Normalized Difference Snow Index (NDSI), the glacier terminus fluctuations of the ice caps from 1973 to 2018 and the Equilibrium Line Altitude (ELA) from 1973 to 2018 are analyzed. The results are compared with climate data, especially with mean summer temperatures and winter precipitation. Due to the negative temperature gradient with increasing altitude, bivariate histograms are generated, showing the glaciated area per altitude zone and time, and providing a prediction of the future development until 2050 and beyond. The results indicate that Langjökull, Hofsjökull and Vatnajökull are retreating and advancing over the study period in correlation with the mean summer temperature, with a steady decrease over time being the clearest and most significant trend. The lower parts of the glaciers, thus, will probably disappear during the next decades. This behaviour is also evident by an exceptional increase of the ELA observed on all three glaciers, which leads to a reduction of the accumulation zone.
Highlights
Glaciers and ice sheets cover about 11% of the Earth’s surface
Recent studies on the mass balance of glaciers and their ice front positions outside Greenland and Antarctica show that the rates of mass loss and retreat of the ice front have accelerated since the 1970s (Carr et al 2014; Cogley 2009; Gardner et al 2013; Jacob et al 2012; Marzeion et al 2012)
With the increasing availability of remote sensing data, the glacier mass balance can be assessed by identifying the snowline on images taken at the end of the ablation season for each year, which can be considered as the equilibrium line (EL) for temperate zone glaciers (Paterson 1994)
Summary
Glaciers and ice sheets cover about 11% of the Earth’s surface. They serve as drinking water reservoirs and are the basis for hydroelectric power, especially in Iceland. Recent studies on the mass balance of glaciers and their ice front positions outside Greenland and Antarctica show that the rates of mass loss and retreat of the ice front have accelerated since the 1970s (Carr et al 2014; Cogley 2009; Gardner et al 2013; Jacob et al 2012; Marzeion et al 2012). Due to their maritime location, Iceland’s glaciers (cf Fig. 1), in particular, are highly sensitive climate indicators and react immediately to shortterm (annual to decadal) climate fluctuations (Bradwell et al 2013; Sigursson et al 2007). With the increasing availability of remote sensing data, the glacier mass balance can be assessed by identifying the snowline on images taken at the end of the ablation season for each year, which can be considered as the equilibrium line (EL) for temperate zone glaciers (Paterson 1994)
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