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Understanding the climate response of the Antarctic Peninsula ice sheet is vital for accurate predictions of sea-level rise. However, since climate models are typically too coarse to capture spatial variability in local scale meteorological processes, our ability to study specific sectors has been limited by the local fidelity of such models and the (often sparse) availability of observations. We show that a high-resolution (5.5 km × 5.5 km) version of a regional climate model (RACMO2.3) can reproduce observed interannual variability in the Larsen B embayment sufficiently to enable its use in investigating long-term changes in this sector. Using the model, together with automatic weather station data, we confirm previous findings that the year of the Larsen B ice shelf collapse (2001/02) was a strong melt year, but discover that total annual melt production was in fact ~30% lower than 2 years prior. While the year before collapse exhibited the lowest melting and highest snowfall during 1980–2014, the ice shelf was likely pre-conditioned for collapse by a series of strong melt years in the 1990s. Melt energy has since returned to pre-1990s levels, which likely explains the lack of further significant collapse in the region (e.g. of SCAR Inlet).

The physical conditions along the Antarctic Peninsula have undergone considerable changes during the last 50 years. A period of pronounced air temperature raise, increasing ocean temperatures as well as changes in the precipitation pattern have been reported by various authors. Consequently, the glacial systems showed changes including widespread retreat, surface lowering as well as increased flow speeds. During the last decades numerous ice shelves along the Antarctic Peninsula retreated, started to break-up or disintegrated completely. The loss of the buttressing effect caused tributary glaciers to accelerate with increasing ice discharge along the Antarctic Peninsula. Quantification of the mass changes is still subject to considerable errors although numbers derived from the different methods are converging. We analysed time series of various SAR satellite sensors (ERS-1/2 SAR, ENVISAT ASAR, RADARSAT-1, ALOS PALSAR, TerraSAR-X/TanDEM-X, Sentinel-1) to detect changes in ice flow speed and surface elevation. The aim is to study the reaction of glaciers to the changing climatic conditions, especially the readjustments of tributary glaciers to ice shelf disintegration, as well as to better quantify the ice mass loss and its temporal changes. We applyed intensity feature tracking techniques on time series from different SAR satellites over the last 20 years to infer changes in glacier surface velocities. Variations in ice front position are mapped in conjunction with the velocity data sets. High resolution bi-static TanDEM-X satellite data was used to derive digital elevation models by differential SAR interferometry. In combination with ASTER and SPOT stereo images, changes in surface elevations were determined. Altimeter data from ICESat, CryoSat-2 and NASA operation IceBridge ATM were used for vertical referencing and quality assessment of the digital elevation models. Airborne laser scanning, ground penetrating radar (AWI Polar-5/6, NASA operation ice-bridge) and

The Antarctic Peninsula has exhibited some of the most spectacular changes observed in glacial systems in recent decades. The events include disintegration of ice shelves, acceleration and thinning of glaciers, variations in the limits between glacier facies, and retreat of glacier fronts. However, due to the lack of both consistent systematic observations of the glacial systems and information on their boundary conditions, it is difficult to accurately predict the contribution of Antarctic Peninsula glaciers to sea level rise and further responses of these ice masses to climatic and oceanographic changes. In this context, the activities of the GLIMS Regional Center for the Antarctic Peninsula and its network of international collaborators are based on the use of various types of Earth observation imagery, mainly optical and radar data. Although a complete glacier inventory is still lacking, we present the results of changes in glacier frontal positions and boundaries of glacier facies as well as links to dynamical adjustments for various locations in the Antarctic Peninsula’s ice masses. Evaluation of Advanced Spaceborne Thermal Emission and reflection Radiometer (ASTER) digital elevation models generated for the Antarctic Peninsula is also discussed.

Recent unexpected changes in the Antarctic Ice Sheet, including ice sheet thinning, ice shelf collapse and changes in ice velocities, along with the recent realization that as much as one third of ice shelf mass loss is due to bottom melt, place a new urgency on understanding the processes involved in these changes. Technological advances, including very new or forthcoming satellite-based (e.g. ICESat, CryoSat) remote sensing missions, will improve our ability to make meaningful determinations of changes in Antarctic Ice Sheet mass balance. This paper is the result of a workshop held to develop a strategy for international collaboration aimed at the collection and synthesis of Antarctic Ice Sheet mass balance data, and at understanding the processes involved so that we might predict future change. Nine sets of recommendations are made, concerning the most important and sensitive measurements, temporal ranges and study areas. A final tenth recommendation calls for increased synthesis of ice sheet data and communication between the field measurement, satellite observation and modelling communities.

Changes of Larsen Ice Shelf, Antarctica, and the surrounding glaciers after its collapse in 1995 were investigated using satellite radar imagery, with emphasis onchanges in the glaciers which previously nourished the ice shelf north of Seal Nunataks. The large glaciers retreated several kilometres inland of the previousgrounding line. The velocity field of Drygalski Glacier, the largest glacier in this area, was mapped by means of interferograms derived from pairs of ERS syntheticaperture radar images from 1995 and 1999. The main part of the glacier showed significant acceleration of flow over these 4 years, with an increase of veocity upto three-fold at the terminus. Similar accelerations were observed by means of interferometry on several other grounded glaciers, suggesting that the removal ofice shelves could lead to an effect on eustatic sea level. For Larsen B, the northernmost surviving part of Larsen Ice Shelf, the retreat of the ice front to October2000 is documented.

Measurements of ice thickness on the Antarctic ice sheet collected during surveys undertaken over the past 50 years have been brought together into a single database. From these data, a seamless suite of digital topographic models have been compiled for Antarctica and its surrounding ocean. This includes grids of ice sheet thickness over the grounded ice sheet and ice shelves, water column thickness beneath the floating ice shelves, bed elevation beneath the grounded ice sheet, and bathymetry to 60°S, including the sub-ice-shelf cavities. These grids are consistent with a recent high-resolution surface elevation model of Antarctica. While the digital models have a nominal spatial resolution of 5 km, such high resolution is justified by the original data density only over a few parts of the ice sheet. The suite does, however, provide an unparalleled vision of the geosphere beneath the ice sheet and a more reliable basis for ice sheet modeling than earlier maps. The total volume of the Antarctic ice sheet calculated from the BEDMAP grid is 25.4 million km3, and the total sea level equivalent, derived from the amount of ice contained within the grounded ice sheet, is 57 m, comprising 52 m from the East Antarctic ice sheet and 5 m from the West Antarctic ice sheet, slightly less than earlier estimates. The gridded data sets can be obtained from the authors.

The motion field of the northern Larsen Ice Shelf, Antarctic Peninsula, was analyzed using radar interferometry in combination with field measurements and finite element model calculations. The ice shelf between Jason Peninsula and Seal Nunataks is in steady retreat since January 1995. Model calculations suggest that the ice shelf is in a stage of irreversible retreat since the last calving events in summer 1998/1999. The interferometric analysis is based on SAR data of the Tandem mission of ERS-1 and ERS-2 in austral spring 1995. The phase contributions due to tidal motion were estimated from the vertical displacement at those parts of the grounding zone where the horizontal motion is close to zero in order to separate the vertical and horizontal motion components over the ice shelf. Satellite derived velocities compare well with the long-term field measurements along a transverse and a longitudinal profile. The real interferograms and synthetic interferograms, calculated from model velocities, show reasonable agreement over the main parts of the ice shelf, but differ in the boundary zones where the details are not resolved by the model.

The motion field of the northern Larsen Ice Shelf, Antarctic Peninsula, was analyzed, based on Landsat data from 1986 to 1989, ERS-SAR data from1992 to 1997, and comparative field measurements along three transects. During this period the northern sections of the ice shelf showed steadyretreat, which culminated in the disintegration of the two ice shelf sections north of the Seal Nunataks in January 1995. Velocities of these two sectionswere derived by cross-correlation, using SAR images of one-year time intervals and Landsat images of one- to three-year intervals. A slight increaseof velocity was observed, as crevasses and rifts opened before the final disintegration. In addition, an interferometric motion analysis was carried outfor the ice shelf around and south of Seal Nunataks based on an image pair from the ERS-1/ERS-2 Tandem Mission in 1995. This analysis reveals acomplex pattern of tidal flexure in the grounding zones, as well as rifting and shear zones on the ice shelf. In addition, the motion of the main inputglaciers was derived.

A variety of data are used to investigate Larsen B, which is at present the northernmost section of the Larsen Ice Shelf. Recently declassified USArgon satellite photographs of 1963, Kosmos photographs of 1975, Landsat images of 1986, 1988 and 1990, ERS-1/2 SAR images from 1992 to1997, Radarsat of 1998 and field surveys are used to analyze the areal extent, surface characteristics and dynamic behaviour of this ice shelf sectionover more than three decades. Visible and radar imagery together with field observations are used synergistically to describe the ice shelf morphology,including meltwater features and rifts. In contrast to the retreat of the ice shelf sections in the north, Larsen B advanced steadily from 1963 to early1995 when the area decreased significantly due to a major calving event. Analysis of different satellite images indicates that melting is proceedingfurther south in coincidence with the regional warming trend. In addition, fracturing processes and rapid development of new rifts are observed,associated with recent acceleration of ice motion close to the front. All observations indicate that major calving events should be expected for this iceshelf section in the near future.

Observations of the retreat and disintegration of ice shelves around the Antarctic Peninsula during the last three decades and associated changes in airtemperature, measured at various meteorological stations on the Antarctic Peninsula, are reviewed. The climatically induced retreat of the northernLarsen Ice Shelf on the east coast and of the Wordie, George VI, and Wilkins ice shelves on the west coast amounted to about 10 000 km2 since themid 1960s. A summary is presented on the recession history of the Larsen Ice Shelf and on the collapse of that sections north of Robertson Island inearly 1995. The area changes were derived from images of various satellites, dating back to late 1963 due to an image from the recently declassifiedUS Argon space missions. This photograph reveals a previously unknown, minor advance of the northern Larsen Ice Shelf before 1975. During theperiod of retreat a consistent and pronounced warming trend was observed at the stations on both east and west coast of the Antarctic Peninsula but amajor cause of the fast retreat and final collapse of the northernmost sections of the Larsen Ice Shelf were several unusually warm summers. Atemperature record from the nearby station Marambio shows that a positive mean summer temperature was reached for the first time in 1992-93.Recent observations indicate that the process of ice shelf disintegration is proceeding further south on both sides of the Antarctic Peninsula.

Air temperatures at the stations Marambio, Esperanza and Matienzo have been analysed to investigate recent climate change on the eastern part of the Antarctic Peninsula. The data are compared with the station Orcadas on the South Orkney Islands, the longest record available in Antarctica, and with Faraday on the western coast of the Peninsula. Though the interannual variability is comparatively high and the stations are located in different climatic regimes, a pronounced warming trend shows-up in all records. At Marambio a temperature increase of 1.5°C has been observed since the beginning of the record in 1971. This is of similar magnitude as the increase at the station Faraday on the west coast with 2.5°C for the longer period since 1945. The steady retreat and collapse of the northern Larsen Ice Shelf coincided with this warming trend. Of particular importance for the ice shelf mass balance in this region are the summer temperatures which show a statistically significant warming trend at the stations Marambio and Esperanza. The representativity of the summer temperatures of Marambio for northern Larsen Ice Shelf is confirmed by intercomparison with the parallel measurements at Matienzo which is located on the ice shelf.

Areal changes and flow dynamics of glaciers of the Southern Patagonian Icefield (SPI) and of northern Larsen Ice Shelf (LIS) on the Antarctic Peninsula have been investigated based on ERS-1 and ERS-2 SAR data and on field work. After a period of steady retreat, coinciding with regional atmospheric warming during the last five decades, the two northernmost sections of the LIS (north of 65°S) disintegrated within a few days in early 1995. At the same time a large calving event occurred also in the section of the LIS south of 65°S. Recent observations of the ice front and of rifting zones indicate that the retreat of this section might accelerate in the near future. Studies of major outlet glaciers on the east side of the SPI, which extends from 48.3°S to 51.5°S, revealed significant retreat for the majority of glaciers. As an example, areal changes of Upsala Glacier, calving into Lago Argentino, are shown. The retreat accelerated considerably after 1993 resulting in unusually large calving events. The region Patagonia - Antarctic Peninsula, located in the west wind zone, reveals steep climatic gradients and therefore is particularly sensitive to climate change as indicated by the retreat of glaciers and ice shelves.