Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, w... more Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, we document changes for the Mittivakkat Gletscher, the only glacier in Greenland with long-term mass balance observations and surface velocity measurements (since 1995). Between 1986 and 2011, this glacier shrank by 18 % in surface 5 area, 20 % in mean ice thickness, and 33 % in volume. We attribute these changes to summertime warming and to drier winter conditions. Meanwhile, the annual mean ice surface velocity decreased by 30 %, likely as a dynamic result of thinning. This dynamic thinning is predicted by ice deformation theory but has rarely been observed on decadal time scales. Mittivakkat Gletscher summer surface velocities were on average 10 50-60 % above winter background values, and up to 160 % higher during peak velocity events. The transition from winter to summer values followed the onset of positive temperatures. Satellite observations show area losses for most other glaciers in the region; these glaciers are likely also to have lost volume (in average around one-third) and slowed down in recent decades. 15
Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series... more Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series compiled from coastal meteorological stations in Greenland and Greenland Ice Sheet (GrIS) ice cores (including three new ice core records from ACT11D, Tunu2013, and Summit2010). The dataset covers the period from 1890 to 2012, a period of climate warming. For approximately the first decade of the new millennium (2001-2012) minimum and maximum mean annual precipitation conditions are found in Northeast Greenland (Tunu2013 c. 120 mm water equivalent (w.e.) year −1 ) and South Greenland (Ikerasassuaq: c. 2300 mm w.e. year −1 ), respectively. The coastal meteorological stations showed on average increasing trends for 1890-2012 (3.5 mm w.e. year −2 ) and 1961-2012 (1.3 mm w.e. year −2 ). Years with high coastal annual precipitation also had a: (1) significant high number of precipitation days (r 2 = 0.59); and (2) high precipitation intensity measured as 24-h precipitation (r 2 = 0.54). For the GrIS the precipitation estimated from ice cores increased on average by 0.1 mm w.e. year −2 , showing an antiphase variability in precipitation trends between the GrIS and the coastal regions. Around 1960 a major shift occurred in the precipitation pattern towards wetter precipitation conditions for coastal Greenland, while drier conditions became more prevalent on the GrIS. Differences in precipitation trends indicate a heterogeneous spatial distribution of precipitation in Greenland. An Empirical Orthogonal Function analysis reveals a spatiotemporal cycle of precipitation that is linked instantaneously to the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation and with an ∼6 years lag time response to the Greenland Blocking Index.
We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and... more We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and 2005-2007 to study the seasonal evolution of supra-glacial lakes in three different regions of the Greenland Ice Sheet. Lake area estimates were obtained by developing an automated classification method for their identification based on 250 m resolution MODIS surface reflectance observations. Widespread supra-glacial lake formation and drainage is observed across the ice sheet, with a 2-3 week delay in the evolution of total supra-glacial lake area in the northern areas compared to the south-west. The onset of lake growth varies by up to one month inter-annually, and lakes form and drain at progressively higher altitudes during the melt season. A positive correlation was found between the annual peak in total lake area and modelled annual runoff. High runoff and lake extent years are generally characterised by low accumulation and high melt season temperatures, and vice versa. Our results indicate that, in a future warmer climate [Meehl, G.
Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, w... more Glaciers in Southeast Greenland have thinned and receded during the past several decades. Here, we document changes for the Mittivakkat Gletscher, the only glacier in Greenland with long-term mass balance observations and surface velocity measurements (since 1995). Between 1986 and 2011, this glacier shrank by 18 % in surface 5 area, 20 % in mean ice thickness, and 33 % in volume. We attribute these changes to summertime warming and to drier winter conditions. Meanwhile, the annual mean ice surface velocity decreased by 30 %, likely as a dynamic result of thinning. This dynamic thinning is predicted by ice deformation theory but has rarely been observed on decadal time scales. Mittivakkat Gletscher summer surface velocities were on average 10 50-60 % above winter background values, and up to 160 % higher during peak velocity events. The transition from winter to summer values followed the onset of positive temperatures. Satellite observations show area losses for most other glaciers in the region; these glaciers are likely also to have lost volume (in average around one-third) and slowed down in recent decades. 15
Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series... more Here, we present an analysis of monthly, seasonal, and annual long-term precipitation time-series compiled from coastal meteorological stations in Greenland and Greenland Ice Sheet (GrIS) ice cores (including three new ice core records from ACT11D, Tunu2013, and Summit2010). The dataset covers the period from 1890 to 2012, a period of climate warming. For approximately the first decade of the new millennium (2001-2012) minimum and maximum mean annual precipitation conditions are found in Northeast Greenland (Tunu2013 c. 120 mm water equivalent (w.e.) year −1 ) and South Greenland (Ikerasassuaq: c. 2300 mm w.e. year −1 ), respectively. The coastal meteorological stations showed on average increasing trends for 1890-2012 (3.5 mm w.e. year −2 ) and 1961-2012 (1.3 mm w.e. year −2 ). Years with high coastal annual precipitation also had a: (1) significant high number of precipitation days (r 2 = 0.59); and (2) high precipitation intensity measured as 24-h precipitation (r 2 = 0.54). For the GrIS the precipitation estimated from ice cores increased on average by 0.1 mm w.e. year −2 , showing an antiphase variability in precipitation trends between the GrIS and the coastal regions. Around 1960 a major shift occurred in the precipitation pattern towards wetter precipitation conditions for coastal Greenland, while drier conditions became more prevalent on the GrIS. Differences in precipitation trends indicate a heterogeneous spatial distribution of precipitation in Greenland. An Empirical Orthogonal Function analysis reveals a spatiotemporal cycle of precipitation that is linked instantaneously to the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation and with an ∼6 years lag time response to the Greenland Blocking Index.
We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and... more We used 268 cloud-free Moderate-resolution Imaging Spectroradiometer (MODIS) images from 2003 and 2005-2007 to study the seasonal evolution of supra-glacial lakes in three different regions of the Greenland Ice Sheet. Lake area estimates were obtained by developing an automated classification method for their identification based on 250 m resolution MODIS surface reflectance observations. Widespread supra-glacial lake formation and drainage is observed across the ice sheet, with a 2-3 week delay in the evolution of total supra-glacial lake area in the northern areas compared to the south-west. The onset of lake growth varies by up to one month inter-annually, and lakes form and drain at progressively higher altitudes during the melt season. A positive correlation was found between the annual peak in total lake area and modelled annual runoff. High runoff and lake extent years are generally characterised by low accumulation and high melt season temperatures, and vice versa. Our results indicate that, in a future warmer climate [Meehl, G.
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