Glacier area and length changes in Norway from repeat inventories

Abstract

Abstract. In this study, we assess glacier area and length changes in mainland Norway from repeat Landsat TM/ETM+-derived inventories and digitized topographic maps. The multi-temporal glacier inventory consists of glacier outlines from three time ranges: 1947 to 1985 (GI n50 ), 1988 to 1997 (GI 1990), and 1999 to 2006 (GI 2000. For the northernmost regions, we include an additional inventory (GI 1900 ) based on historic maps surveyed between 1895 and 1907. Area and length changes are assessed per glacier unit, 36 subregions, and for three main parts of Norway: southern, central, and northern. The results show a decrease in the glacierized area from 2994 km 2 in GI n50 to 2668 km 2 in GI 2000 (total 2722 glacier units), corresponding to an area reduction of −326 km 2 , or −11 % of the initial GI n50 area. The average length change for the full epoch (within GI n50 and GI 2000 ) is −240 m. Overall, the comparison reveals both area and length reductions as general patterns, even though some glaciers have advanced. The three northernmost subregions show the highest retreat rates, whereas the central part of Norway shows the lowest change rates. Glacier area and length changes indicate that glaciers in maritime areas in southern Norway have retreated more than glaciers in the interior, and glaciers in the north have retreated more than southern glaciers. These observed spatial trends in glacier change are related to a combination of several factors such as glacier geometry, elevation, and continentality, especially in southern Norway.

ICESat laser altimetry over small mountain glaciers

“…This is in line with the findings of e.g. Zemp et al (2015) or Cogley (2009), who assign differences in mass budgets as from glaciological vs. geodetic measurements to sample composition rather than method-inherent causes. We find that with ICESat's random spatial sampling (with respect to glacier locations), we also capture many small ice bodies and snow patches.…”

“…This is also reflected in measured glacier net balance magnitudes (Kjøllmoen et al, 2011). The Norwe-gian glacier area has recently been mapped by the Norwegian Water Resources and Energy Directorate (NVE) based on Landsat imagery from 1999 to 2006 (Andreassen and Winsvold, 2012;Winsvold et al, 2014; digital data available from NVE, 2016; or the Global Land Ice Measurements from Space (GLIMS) database: GLIMS and NSIDC, 2012). Glaciers cover 1522 km 2 or roughly 1.5 % of our study area.…”

“…Retreat of mountain glaciers is also a major cause of eustatic sea level rise (Gardner et al, 2013), but the response of some large glacierized systems to climatic changes is still poorly quantified, especially in regions with large climatic variability. The glacier regions least represented in long-term in situ glacier monitoring programmes are those with the largest ice volumes (Zemp et al, 2015), which are less inhabited and difficult to access and, therefore, are not well studied. Regional estimates of ice loss recently gained importance, not least for assessing the current and future contribution of water stored in land ice masses to sea level rise (Gardner et al, 2013;Jacob et al, 2012;Marzeion et al, 2012;Radić et al, 2014;Radić and Hock, 2011) and for quantifying current run-off contribution from glacier imbalance (Kääb et al, 2015) or changes in the upstream cryosphere (e.g.…”

The European mountain cryosphere: a review of its current state, trends, and future challenges

“…A loss of 49 % in the ice volume was estimated for the European Alps for the period 1900-2011 (Huss, 2012). Repeat inventories have shown a reduction in glacier area of 11 % in Norway between 1960 and the 2000s (−0.28 % yr −1 ) (Winsvold et al, 2014) and 28 % in Switzerland between 1973 and 2010 (−0.76 % yr −1 ) (Fischer et al, 2014). Periods with positive surface mass balance have, however, occurred intermittently, notably from the 1960s to the mid-1980s in the Alps and in the 1990s and 2000s for maritime glaciers in Norway (Zemp et al, 2015;Andreassen et al, 2016).…”

“…Kinematic methods are used to monitor moving permafrost bodies (e.g., rock glaciers) and surface geometry changes. Hereby, methods based on remote sensing allow for kinematic analyses over large scales (Barboux et al, 2014(Barboux et al, , 2015Necsoiu et al, 2016) and the compilation of rock-glacier inventories (e.g., Schmid et al, 2015), whereas ground-based and airborne kinematic methods focus on localized regions and on the detection of permafrost degradation over longer timescales (Kaufmann, 2012;Klug et al, 2012;Barboux et al, 2014;Müller et al, 2014;Kenner et al, 2014Kenner et al, , 2016Wirz et al, 2014Wirz et al, , 2016. Long-term monitoring of creeping permafrost bodies shows an acceleration in motion during recent years, possibly related to increasing ground temperatures and higher internal water content (Delaloye et al, 2008;Ikeda et al, 2008;Permos, 2016;Scotti et al, 2016;Hartl et al, 2016).…”