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We combined an ensemble of satellite altimetry, interferometry, and gravimetry data sets using common geographical regions, time intervals, and models of surface mass balance and glacial isostatic adjustment to estimate the mass balance of Earth's polar ice sheets. We find that there is good agreement between different satellite methods--especially in Greenland and West Antarctica--and that combining satellite data sets leads to greater certainty. Between 1992 and 2011, the ice sheets of Greenland, East Antarctica, West Antarctica, and the Antarctic Peninsula changed in mass by -142 ± 49, +14 ± 43, -65 ± 26, and -20 ± 14 gigatonnes year(-1), respectively. Since 1992, the polar ice sheets have contributed, on average, 0.59 ± 0.20 millimeter year(-1) to the rate of global sea-level rise.

NASA's ITS_LIVE project delivers information on global glacier dynamics and provides historical context for climate change with a record of how every glacier in the world has evolved over decades of satellite observation. To handle petabytes of data in the satellite archives and a constant influx of new observations, the project has adopted a cloud-native approach that is scalable, performant, user friendly, and embraces transparent and collaborative code development. As every discipline of Earth science is being transformed by a new era of remote sensing and cloud computing, ITS_LIVE offers a progressive approach to maximizing scientific advancements through open science. [ABSTRACT FROM AUTHOR]

The world's icy and snowy regions—the cryosphere—are where the most profound changes will occur as the globe continues warming. In many areas, the levels of cryospheric change today are surpassing any seen in the past hundreds to thousands of years. This amplified response has a simple explanation: Most of the cryosphere is, on average, near the freezing point. Small shifts in temperature push large regions to a different physical state. However, while the processes leading to the loss of ice are quickly started, they do not quickly stop. We are on the verge of committing ourselves to sizable increases in sea level. The 2007 Intergovernmental Panel on Climate Change (IPCC) report estimated sea level rise in this century at just 20 to 60 centimeters, but that total did not include contributions from the break-up and flow of ice sheets. The melting of mountain glaciers and ice in Greenland and Antarctica could add an additional meter of sea level rise. An equally important effect may be the feedback that changes in ice—especially the ice-covered ocean—have on climate in both the polar and the temperate regions of the world. The author describes the processes that are rapidly eroding polar ice. [ABSTRACT FROM AUTHOR]

Observations of Southern Hemisphere sea ice from passive microwave satellite measurements show that a new record maximum extent of 19.58 × 106 km2 was reached on 30 September 2013; the extent is just over two standard deviations above the 1979-2012 mean and follows a similar record (19.48 × 106 km2) in 2012. On the record day in 2013, sea-ice extent was greater than the 30 year average (1981-2010) in nearly all Southern Ocean regions. For the year as a whole, Southern Hemisphere sea-ice area and extent were well above average, and numerous monthly and daily records were broken. Analysis of anomaly patterns and the atmospheric and oceanic events suggests that a sequence of regional wind and cold-freshened surface waters is likely responsible for the record maximum and the generally high 2013 extent. In particular, the Ross Sea sector experienced a combination of cold southerly winds associated with the position and depth of the Amundsen Sea low, and lower than normal sea surface temperatures (up to 2°C below normal). The resulting very high anomaly in ice extent in this region was a major component of the overall record maximum. [ABSTRACT FROM AUTHOR]

Blue-ice areas (BIAs) and their geographical distribution in Antarctica were mapped using Landsat-7 ETM+ images with 15m spatial resolution obtained during the 1999-2003 austral summers and covering the area north of 82.5° S, and a snow grain-size image of the MODIS-based Mosaic of Antarctica (MOA) dataset with 125m grid spacing acquired during the 2003/04 austral summer from 82.5° S to the South Pole. A map of BIAs was created with algorithms of thresholds based on band ratio and reflectance for ETM+ data and thresholds based on snow grain size for the MOA dataset. The underlying principle is that blue ice can be separated from snow or rock by their spectral discrepancies and by different grain sizes of snow and ice. We estimate the total area of BIAs in Antarctica during the data acquisition period is 234 549km², or 1.67% of the area of the continent. Blue ice is scattered widely over the continent but is generally located in coastal or mountainous regions. The BIA dataset presented in this study is the first map covering the entire Antarctic continent sourced solely from ETM+ and MODIS data. This dataset can potentially benefit other studies in glaciology, meteorology, climatology and paleoclimate, meteorite collection and airstrip site selection. [ABSTRACT FROM AUTHOR]

Abstract: Satellite remote sensing observations of three break-up events in 2008 for the Wilkins Ice Shelf (28 February to 6 March, 27 May to 31 May, and 28 June to mid-July) provide unprecedented detail of ice shelf calving during rapid break-up. The observations reveal that the Wilkins break-ups occur through a distinctive type of shelf calving, which we term ‘disintegration’, as well as more typical rifting and calving. Here we focus on the disintegration process, which is characterized by repeated rapid fracturing that creates narrow ice-edge-parallel blocks, with subsequent block toppling and fragmentation forming an expanding iceberg and ice rubble mass. We use these data to develop and test a model of floating ice plate disintegration in which ice plate bending stresses at the ice front arising from buoyancy forces can lead to runaway calving when free (mobile) water is available. High-resolution satellite images and laser altimetry of the first break-up event provide details of fracture spacings, ice thicknesses, and plate bending profiles that agree well with our model predictions. We suggest that surface or near-surface meltwater is the main pre-condition for disintegration, and that hydro-fracture is the main mechanism. Brine layers from near-waterline brine infiltration can support a similar process, but this is less effective unless regional ice stress patterns contribute to the net stress available at the crack tip for fracturing. A combination of brine-enhanced fracturing and changing internal net extensional stresses was the likely mechanism behind the latter two Wilkins events. [Copyright &y& Elsevier]

Abstract: Glaciers that flowed into the former Larsen B ice shelf have responded to its March 2002 disintegration in different ways. The responses include prolonged front retreat, advance followed by retreat, and maintenance of a stable front position. Retreating glaciers initially accelerated and thinned dramatically, although the rate of change has since declined on at least one large glacier. Here, response patterns are documented and discussed in the context of tidewater glacier processes. The different responses observed around the Larsen B embayment demonstrate the importance of the three-dimensional, geographic setting when considering the response of outlet glaciers to perturbations at their downstream ends. [Copyright &y& Elsevier]

Understanding the mechanisms that drive the mass imbalance of the Greenland ice sheet (GrIS) is critical to the accurate projection of its contribution to future sea level rise. Greenland's ice mass loss has been accelerating recently. Using satellite Earth-gravity and regional climate model data, we show that the acceleration rate of Greenland ice mass loss from 2003 to 2012 is − 13.9 ± 2.0 Gt/yr 2 , which results mainly from an increase of meltwater runoff (− 6.3 ± 1.1 Gt/yr 2 ) and a decrease of precipitation (− 4.8 ± 1.1 Gt/yr 2 ). Before the extreme surface melting in the summers of 2010 and 2012, the decrease of precipitation (− 9.7 ± 2.5 Gt/yr 2 ) was a larger contributor to the ice mass loss acceleration than the increase of runoff (− 2.1 ± 2.2 Gt/yr 2 ). Furthermore, we show that the North Atlantic Oscillation (NAO) is linked to the precipitation decrease during summer, and its recent influence to Greenland is anomalously large possibly due to the change in atmospheric circulation in the North Atlantic. These results indicate that inter-annual climate variability is playing a significant role in the recently observed Greenland ice mass loss acceleration, underscoring the difficulty of projecting future sea level rise based on the recent observations of GrIS mass loss. [ABSTRACT FROM AUTHOR]