Changes In Ice Dynamics Research Articles

Examining the effect of ice dynamic changes on subglacial hydrology through modelling of a synthetic Antarctic glacier

Abstract Hydrologic pathways beneath ice sheets and glaciers play an important role in regulating ice flow. Antarctica has experienced, and will continue to experience, changes in ice dynamics and geometry, but the associated changes in subglacial hydrology have received less attention. Here, we use the GlaDS subglacial hydrology model to examine drainage evolution beneath an idealised Antarctic glacier in response to steepening ice surface slopes, accelerating ice velocities and subglacial lake drainages. Ice surface slope changes exerted a dominant influence, redirecting basal water to different outlet locations and substantially increasing channelised discharge crossing the grounding line. Faster ice velocities had comparatively negligible effects. Subglacial lake drainage results indicated that lake refilling times play a key role in drainage system evolution, with lake flux more readily accommodated following shorter refilling times. Our findings are significant for vulnerable Antarctic regions currently experiencing dynamic thinning since subglacial water re-routing could destabilise ice shelves through enhanced sub-shelf melting, potentially hastening irreversible retreat. These changes could also affect subglacial lake activity. We, therefore, emphasise that including a nuanced and complex representation of subglacial hydrology in ice-sheet models could provide critical information on the timing and magnitude of sea-level change contributions from Antarctica.

Modeling changes in ice dynamics and subsurface thermal structure in Lake Michigan-Huron between 1979 and 2021

The world’s largest lakes, including the Laurentian Great Lakes, have experienced significant surface warming and loss of ice cover over the last several decades. Although changing surface conditions have received substantial research interest, changes below the surface remain largely unexplored, despite their importance for turbulent mixing, nutrient cycling, and primary production. In this study, we investigate changes in subsurface thermal structure and timing in Lake Michigan-Huron related to ongoing climate warming. This work utilizes atmospheric reanalysis data to drive the Great Lakes Finite Volume Community Ocean Model (GL-FVCOM), providing three-dimensional hydrodynamic and ice simulations between 1979 and 2021. Results are used to analyze trends in ice and temperature dynamics, revealing significant changes in annually averaged ice cover (− 2.1– − 5.2%/decade), ice thickness (− 0.68 – − 2.0 cm/decade), surface temperature (+ 0.47– + 0.51 ^circ{rm C}/decade), and bottom temperature (+ 0.26– + 0.29 ^circ{rm C}/decade) over the last 40 years, especially in ecologically important bays (e.g., Green Bay, Saginaw Bay). Significant warming was observed at all depth layers (0–270 m), with warming trends in the epilimnion and hypolimnion that agreed well with recent analysis of observational data in Lake Michigan. Shifting stratification dynamics led to dramatic changes in modelled overturning behavior, and earlier spring turnover dates (− 2.2– − 7.5 days/decade) and later fall turnover dates (+ 2.5– + 6.3 days/decade) led to a net lengthening of the stratified period. This study presents one of the most comprehensive analyses of changes in Great Lakes subsurface temperatures to date, providing important context for future climate modelling and coastal management efforts in the region.

A topographic hinge-zone divides coastal and inland ice dynamic regimes in East Antarctica

The impact of late Cenozoic climate on the East Antarctic Ice Sheet is uncertain. Poorly constrained patterns of relative ice thinning and thickening impair the reconstruction of past ice-sheet dynamics and global sea-level budgets. Here we quantify long-term ice cover of mountains protruding the ice-sheet surface in western Dronning Maud Land, using cosmogenic Chlorine-36, Aluminium-26, Beryllium-10, and Neon-21 from bedrock in an inverse modeling approach. We find that near-coastal sites experienced ice burial up to 75–97% of time since 1 Ma, while interior sites only experienced brief periods of ice burial, generally <20% of time since 1 Ma. Based on these results, we suggest that the escarpment in Dronning Maud Land acts as a hinge-zone, where ice-dynamic changes driven by grounding-line migration are attenuated inland from the coastal portions of the East Antarctic Ice Sheet, and where precipitation-controlled ice-thickness variations on the polar plateau taper off towards the coast.

Diagnosing Discrepancies between Observations and Models of Surface Energy Fluxes in a Midlatitude Lake

Abstract The physical processes of heat exchange between lakes and the surrounding atmosphere are important in simulating and predicting terrestrial surface energy balance. Latent and sensible heat fluxes are the dominant physical process controlling ice growth and decay on the lake surface, as well as having influence on regional climate. While one-dimensional lake models have been used in simulating environmental changes in ice dynamics and water temperature, understanding the seasonal to daily cycles of lake surface energy balance and its relationship to lake thermal properties, atmospheric conditions, and how those are represented in models is still an open area of research. We evaluated a pair of one-dimensional lake models, Freshwater Lake (FLake) and the General Lake Model (GLM), to compare modeled latent and sensible heat fluxes against observed data collected by an eddy covariance tower during a 1-yr period in 2017, using Lake Mendota in Madison, Wisconsin, as our study site. We hypothesized transitional periods of ice cover as a leading source of model uncertainty, and we instead found that the models failed to simulate accurate values for large positive heat fluxes that occurred from late August into late December. Our results ultimately showed that one-dimensional models are effective in simulating sensible heat fluxes but are considerably less sensitive to latent heat fluxes than the observed relationships of latent heat flux to environmental drivers. These results can be used to focus future improvement of these lake models especially if they are to be used for surface boundary conditions in regional numerical weather models. Significance Statement While lakes consist of a small amount of Earth’s surface, they have a large impact on local climate and weather. A large amount of energy is stored in lakes during the spring and summer, and then removed from lakes before winter. The effect is particularly noticeable in high latitudes, when the seasonal temperature difference is larger. Modeling this lake energy exchange is important for weather models and measuring this energy exchange is challenging. Here we compare modeled and observed energy exchange, and we show there are large amounts of energy exchange happening in the fall, which models struggle to capture well. During periods of partial ice coverage in early winter, lake behavior can change rapidly.

Beryllium isotope variations recorded in the Adélie Basin, East Antarctica reflect Holocene changes in ice dynamics, productivity, and scavenging efficiency

The Adélie Basin is a relatively small (∼1600 km2), semi-enclosed continental shelf bathymetric depression located adjacent to the Wilkes Subglacial Basin, a basin underlying a sector of the East Antarctic Ice Sheet that contains ∼3–4 m sea level equivalent of ice. Located within the Adélie Basin is a ∼184 m thick laminated sediment deposit, the Adélie Drift, ideal for examining regional changes in ice sheet and ocean dynamics. Here, we examine the ratio of reactive beryllium-10 to reactive beryllium-9 ((10Be/9Be)reac) in a marine sediment core obtained from the Adélie Drift to assess these changes during the Holocene epoch (11.7 ka BP to present). The (10Be/9Be)reac record provides insight into changes in freshwater input, primary productivity, and scavenging efficiency, while removing the influence of particle size on 10Be concentration. During the early Holocene, (10Be/9Be)reac ratios indicate increased meltwater discharge from ca. 11.7 to 10 ka BP, as grounded ice retreated from the Adélie Basin and adjacent bathymetric highs. After ∼10 ka BP, beryllium isotopes are influenced by scavenging efficiency and dilution controlled by ocean currents and accumulation rate, operating alongside meltwater input, suggesting there are additional factors to consider when using (10Be/9Be)reac as a proxy for ice shelf cover and glacial dynamics.

Subglacial controls on dynamic thinning at Trinity-Wykeham Glacier, Prince of Wales Ice Field, Canadian Arctic

ABSTRACTMass loss from glaciers and ice caps represents the largest terrestrial component of current sea level rise. However, our understanding of how the processes governing mass loss will respond to climate warming remains incomplete. This study explores the relationship between surface elevation changes (dh/dt), glacier velocity changes (du/dt), and bedrock topography at the Trinity-Wykeham Glacier system (TWG), Canadian High Arctic, using a range of satellite and airborne datasets. We use measurements of dh/dt from ICESat (2003–2009) and CryoSat-2 (2010–2016) repeat observations to show that rates of surface lowering increased from 4 m yr−1 to 6 m yr−1 across the lowermost 10 km of the TWG. We show that surface flow rates at both Trinity Glacier and Wykeham Glacier doubled over 16 years, during which time the ice front retreated 4.45 km. The combination of thinning, acceleration and retreat of the TWG suggests that a dynamic thinning mechanism is responsible for the observed changes, and we suggest that both glaciers have transitioned from fully grounded to partially floating. Furthermore, by comparing the separate glacier troughs we suggest that the dynamic changes are modulated by both lateral friction from the valley sides and the complex geometry of the bed. Further, the presence of bedrock ridges induces crevassing on the surface and provides a direct link for surface meltwater to reach the bed. We observe supraglacial lakes that drain at the end of summer and are concurrent with a reduction in glacier velocity, suggesting hydrological connections between the surface and the bed significantly impact ice flow. The bedrock topography thus has a primary influence on the nature of the changes in ice dynamics observed over the last decade.

Continent‐Wide, Interferometric SAR Phase, Mapping of Antarctic Ice Velocity

AbstractSurface ice velocity is a fundamental characteristic of glaciers and ice sheets that quantifies the transport of ice. Changes in ice dynamics have a major impact on ice sheet mass balance and its contribution to sea level rise. Prior comprehensive mappings employed speckle and feature tracking techniques, optimized for fast‐flow areas, with precision of 2‐5 m/year, hence limiting our ability to describe ice flow in the slow interior. We present a vector map of ice velocity using the interferometric phase from multiple satellite synthetic aperture radars resulting in 10 times higher precision in speed (20 cm/year) and direction (5°) over 80% of Antarctica. Precision mapping over areas of slow motion (&lt;1 m/year) improves from 20 to 93%, which helps better constrain drainage boundaries, improve mass balance assessment, evaluate regional atmospheric climate models, reconstruct ice thickness, and inform ice sheet numerical models.

Modelling the Antarctic Ice Sheet across the mid-Pleistocene transition – implications for Oldest Ice

Abstract. The international endeavour to retrieve a continuous ice core, which spans the middle Pleistocene climate transition ca. 1.2–0.9 Myr ago, encompasses a multitude of field and model-based pre-site surveys. We expand on the current efforts to locate a suitable drilling site for the oldest Antarctic ice core by means of 3-D continental ice-sheet modelling. To this end, we present an ensemble of ice-sheet simulations spanning the last 2 Myr, employing transient boundary conditions derived from climate modelling and climate proxy records. We discuss the imprint of changing climate conditions, sea level and geothermal heat flux on the ice thickness, and basal conditions around previously identified sites with continuous records of old ice. Our modelling results show a range of configurational ice-sheet changes across the middle Pleistocene transition, suggesting a potential shift of the West Antarctic Ice Sheet to a marine-based configuration. Despite the middle Pleistocene climate reorganisation and associated ice-dynamic changes, we identify several regions conducive to conditions maintaining 1.5 Myr (million years) old ice, particularly around Dome Fuji, Dome C and Ridge B, which is in agreement with previous studies. This finding strengthens the notion that continuous records with such old ice do exist in previously identified regions, while we are also providing a dynamic continental ice-sheet context.

Variability and Predictability of the Bering Strait Ocean Heat Transport and Arctic Ocean Sea Ice Extent

Background: This study examines the monthly, seasonal, and interannual variations in Pacific Ocean heat transport entering the Arctic Ocean through the Bering Strait, and its influence on sea ice extent in the Arctic Ocean. Methods: Monthly ocean heat transport is calculated using temperature and volumetric transport data from moorings deployed in the Bering Strait. Pearson correlations are calculated between the observed detrended monthly cumulative Bering Strait ocean heat transport and the detrended monthly sea ice extent time series from May through September. Results: An increase in the spring variability of the Bering Strait ocean heat transport is found since 2010, associated with both increased volume flux and water temperatures in May and June. A significant negative correlation between the Bering Strait ocean heat transport and Arctic sea ice extent in the Pacific sector is observed for May, June, and July, both within and outside the marginal ice zone, with a sharp decline in predictability for August and September. Conclusion: The Bering Strait ocean heat transport is a skillful predictor for early melt season sea ice extent in the Pacific sector but loses predictive skills later in the summer in August and September due to changes in ice dynamics, in accordance with the loss of predictive skill in Global Climate Models.

Variability in the ice sheet elevations over Antarctica derived from repetitive SARAL/AltiKa radar altimeter data (2013–2016)

Changes in surface elevations of polar ice sheets are the result of changes in ice dynamics and surface mass balance. Here, we present intra- and inter-annual elevation changes over the Antarctic ice sheet using the AltiKa radar altimeter’s 40 Hz geophysical data record products for the period 2013–2016. Slope corrections were applied on the elevations using a digital elevation model (DEM) available from NASA’s ice, cloud and land elevation satellite (ICESat). Comparison of elevations from AltiKa and ICESat’s DEM yielded correlation, bias and root-mean-square-deviation values of the order of 0.99, −2.88 and 23.04 m, respectively, indicating the first-level accuracy of a former dataset. Further comparison of Airborne Topographic Mapper dataset with AltiKa derived elevation yielded 0.4 m root-mean-square-deviation over a part of Vostok subglacial lake. The intra-annual change indicates that for GY2 (glaciological year), GY3 and GY4, number of negative elevation change points exceeded the number of positive elevation change points during the Antarctic austral summer period (December–February). Inter-annual elevation changes were negative during 2013–2014 and positive during 2014–2015 over east Antarctica, whereas in west Antarctica negative elevation changes were observed for both periods.

Global environmental consequences of twenty-first-century ice-sheet melt.

Government policies currently commit us to surface warming of three to four degrees Celsius above pre-industrial levels by 2100, which will lead to enhanced ice-sheet melt. Ice-sheet discharge was not explicitly included in Coupled Model Intercomparison Project phase 5, so effects on climate from this melt are not currently captured in the simulations most commonly used to inform governmental policy. Here we show, using simulations of the Greenland and Antarctic ice sheets constrained by satellite-based measurements of recent changes in ice mass, that increasing meltwater from Greenland will lead to substantial slowing of the Atlantic overturning circulation, and that meltwater from Antarctica will trap warm water below the sea surface, creating a positive feedback that increases Antarctic ice loss. In our simulations, future ice-sheet melt enhances global temperature variability and contributes up to 25 centimetres to sea level by 2100. However, uncertainties in the way in which future changes in ice dynamics are modelled remain, underlining the need for continued observations and comprehensive multi-model assessments.

Changes in glacier dynamics in the northern Antarctic Peninsula since 1985

Abstract. The climatic conditions along the northern Antarctic Peninsula have shown significant changes within the last 50 years. Here we present a comprehensive analysis of temporally and spatially detailed observations of the changes in ice dynamics along both the east and west coastlines of the northern Antarctic Peninsula. Temporal evolutions of glacier area (1985–2015) and ice surface velocity (1992–2014) are derived from a broad multi-mission remote sensing database for 74 glacier basins on the northern Antarctic Peninsula ( &lt; 65° S along the west coast and north of the Seal Nunataks on the east coast). A recession of the glaciers by 238.81 km2 is found for the period 1985–2015, of which the glaciers affected by ice shelf disintegration showed the largest retreat by 208.59 km2. Glaciers on the east coast north of the former Prince Gustav Ice Shelf extent in 1986 receded by only 21.07 km2 (1985–2015) and decelerated by about 58 % on average (1992–2014). A dramatic acceleration after ice shelf disintegration with a subsequent deceleration is observed at most former ice shelf tributaries on the east coast, combined with a significant frontal retreat. In 2014, the flow speed of the former ice shelf tributaries was 26 % higher than before 1996. Along the west coast the average flow speeds of the glaciers increased by 41 %. However, the glaciers on the western Antarctic Peninsula revealed a strong spatial variability of the changes in ice dynamics. By applying a hierarchical cluster analysis, we show that this is associated with the geometric parameters of the individual glacier basins (hypsometric indexes, maximum surface elevation of the basin, flux gate to catchment size ratio). The heterogeneous spatial pattern of ice dynamic evolutions at the northern Antarctic Peninsula shows that temporally and spatially detailed observations as well as further monitoring are necessary to fully understand glacier change in regions with such strong topographic and climatic variances.

Future sea level change from Antarctica's Lambert‐Amery glacial system

AbstractFuture global mean sea level (GMSL) change is dependent on the complex response of the Antarctic ice sheet to ongoing changes and feedbacks in the climate system. The Lambert‐Amery glacial system has been observed to be stable over the recent period yet is potentially at risk of rapid grounding line retreat and ice discharge given that a significant volume of its ice is grounded below sea level, making its future contribution to GMSL uncertain. Using a regional ice sheet model of the Lambert‐Amery system, we find that under a range of future warming and extreme scenarios, the simulated grounding line remains stable and does not trigger rapid mass loss from grounding line retreat. This allows for increased future accumulation to exceed the mass loss from ice dynamical changes. We suggest that the Lambert‐Amery glacial system will remain stable or gain ice mass and mitigate a portion of potential future sea level rise over the next 500 years, with a range of +3.6 to −117.5 mm GMSL equivalent.

Comprehensive Annual Ice Sheet Velocity Mapping Using Landsat-8, Sentinel-1, and RADARSAT-2 Data

Satellite remote sensing data including Landsat-8 (optical), Sentinel-1, and RADARSAT-2 (synthetic aperture radar (SAR) missions) have recently become routinely available for large scale ice velocity mapping of ice sheets in Greenland and Antarctica. These datasets are too large in size to be processed and calibrated manually as done in the past. Here, we describe a methodology to process the SAR and optical data in a synergistic fashion and automatically calibrate, mosaic, and integrate these data sets together into seamless, ice-sheet-wide, products. We employ this approach to produce annual mosaics of ice motion in Antarctica and Greenland with all available data acquired on a particular year. We find that the precision of a Landsat-8 pair is lower than that of its SAR counterpart, but due to the large number of Landsat-8 acquisitions, combined with the high persistency of optical surface features in the Landsat-8 data, we obtain accurate velocity products from Landsat that integrate well with the SAR-derived velocity products. The resulting pool of remote sensing products is a significant advance for observing changes in ice dynamics over the entire ice sheets and their contribution to sea level. In preparation for the next generation sensors, we discuss the implications of the results for the upcoming NASA-ISRO SAR mission (NISAR).

Assessing small-scale deformation and stability of landfast sea ice on seasonal timescales through L-band SAR interferometry and inverse modeling

Rapid environmental change and increases in use of shorefast ice by industry and coastal communities highlight the need for an approach to accurately assess landfast sea-ice stability on seasonal timescales. While stability can sometimes be inferred from field measurements, current methods are lacking robustness and the ability to be automated and applied over large areas and long time scales to ensure safety and document change in the context of transportation, indigenous ice uses and industrial development. This paper introduces an inverse model capable of reconstructing three-dimensional deformation fields from one-dimensional interferometric L-band Synthetic Aperture Radar (SAR) phase patterns. We apply this method at three landfast ice locations on the Alaska Beaufort Sea coast near Barrow and Prudhoe Bay. We find the small-scale displacements estimated from the model consistent with regional patterns of ice motion. Our study suggests that interferometry can provide planning and decision-support information for ice road development and structures operating within ice. Moreover, InSAR can potentially increase our understanding of sea ice on a fundamental level in terms of large-scale stability and long-term changes in ice dynamics.

Future sea-level rise from tidewater and ice-shelf tributary glaciers of the Antarctic Peninsula

Iceberg calving and increased ice discharge from ice-shelf tributary glaciers contribute significant amounts to global sea-level rise (SLR) from the Antarctic Peninsula (AP). Owing to ongoing ice dynamical changes (collapse of buttressing ice shelves), these contributions have accelerated in recent years. As the AP is one of the fastest warming regions on Earth, further ice dynamical adjustment (increased ice discharge) is expected over the next two centuries. In this paper, the first regional SLR projection of the AP from both iceberg calving and increased ice discharge from ice-shelf tributary glaciers in response to ice-shelf collapse is presented. An ice-sheet model forced by temperature output from 13 global climate models (GCMs), in response to the high greenhouse gas emission scenario (RCP8.5), projects AP contribution to SLR of 28±16 to 32±16 mm by 2300, partitioned approximately equally between contributions from tidewater glaciers and ice-shelf tributary glaciers. In the RCP4.5 scenario, sea-level rise projections to 2300 are dominated by tidewater glaciers (∼8–18 mm). In this cooler scenario, 2.4±1 mm is added to global sea levels from ice-shelf tributary drainage basins as fewer ice-shelves are projected to collapse. Sea-level projections from ice-shelf tributary glaciers are dominated by drainage basins feeding George VI Ice Shelf, accounting for ∼70% of simulated SLR. Combined total ice dynamical SLR projections to 2300 from the AP vary between 11±2 and 32±16 mm sea-level equivalent (SLE), depending on the emission scenario used. These simulations suggest that omission of tidewater glaciers could lead to a substantial underestimation of the ice-sheet's contribution to regional SLR.

Geostatistical and Statistical Classification of Sea-Ice Properties and Provinces from SAR Data

Recent drastic reductions in the Arctic sea-ice cover have raised an interest in understanding the role of sea ice in the global system as well as pointed out a need to understand the physical processes that lead to such changes. Satellite remote-sensing data provide important information about remote ice areas, and Synthetic Aperture Radar (SAR) data have the advantages of penetration of the omnipresent cloud cover and of high spatial resolution. A challenge addressed in this paper is how to extract information on sea-ice types and sea-ice processes from SAR data. We introduce, validate and apply geostatistical and statistical approaches to automated classification of sea ice from SAR data, to be used as individual tools for mapping sea-ice properties and provinces or in combination. A key concept of the geostatistical classification method is the analysis of spatial surface structures and their anisotropies, more generally, of spatial surface roughness, at variable, intermediate-sized scales. The geostatistical approach utilizes vario parameters extracted from directional vario functions, the parameters can be mapped or combined into feature vectors for classification. The method is flexible with respect to window sizes and parameter types and detects anisotropies. In two applications to RADARSAT and ERS-2 SAR data from the area near Point Barrow, Alaska, it is demonstrated that vario-parameter maps may be utilized to distinguish regions of different sea-ice characteristics in the Beaufort Sea, the Chukchi Sea and in Elson Lagoon. In a third and a fourth case study the analysis is taken further by utilizing multi-parameter feature vectors as inputs for unsupervised and supervised statistical classification. Field measurements and high-resolution aerial observations serve as basis for validation of the geostatistical-statistical classification methods. A combination of supervised classification and vario-parameter mapping yields best results, correctly identifying several sea-ice provinces in the shore-fast ice and the pack ice. Notably, sea ice does not have to be static to be classifiable with respect to spatial structures. In consequence, the geostatistical-statistical classification may be applied to detect changes in ice dynamics, kinematics or environmental changes, such as increased melt ponding, increased snowfall or changes in the equilibrium line.

Spatial analysis of trends in primary production and relationship with large‐scale climate variability in the Ross Sea, Antarctica (1997–2013)

AbstractRecent studies have documented an increase in sea ice extent and the duration of the ice season in the Ross Sea, Antarctica. We conducted a satellite‐based study to quantify changes in net primary production (NPP) and chlorophyll a (Chl a) in response to the observed changes in ice dynamics in the Ross Sea south of 60°S. Our study covers a 16 year time period (1997–2013) and incorporates both the shelf and off‐shelf regions of the Ross Sea. We observed significant secular changes in NPP from 1997 to 2013 in the off‐shelf region, with NPP increasing on the eastern side and decreasing on the western side of our study area. The changes we observed in NPP are consistent with the changes we observed in sea surface temperature (SST) and open water days (OWDs), decreasing (increasing) on the western (eastern) side of our study area. Finally, we examined the influence of the Southern Annular Mode (SAM) and the El Niño Southern Oscillation (ENSO), on SST, OWDs, Chl a, and NPP in the Ross Sea and observed a significant relationship between the state of the SAM and ENSO and SST, OWDs, and NPP across the study region. The response of OWDs, SST, and NPP to atmospheric forcing by SAM and ENSO was opposite for the shelf and off‐shelf regions, such that during a positive phase of SAM or negative phase of ENSO (La Niña), SST, OWDs, and NPP increased on the shelf and decreased in the off‐shelf region.

Glacier velocities and dynamic discharge from the ice masses of Baffin Island and Bylot Island, Nunavut, Canada

Speckle tracking of ALOS PALSAR fine beam data from 2007–2011 are used to determine the surface motion of major ice masses on Baffin Island and Bylot Island in the southern Canadian Arctic Archipelago. Glacier velocities are low overall, with peaks of ∼100 m a−1 and means of ∼20–60 m a−1 common along the main trunk of many outlet glaciers. Peak velocities on Penny and Bylot Island ice caps tend to occur near the mid-sections of their primary outlet glaciers, while the fastest velocities on all other glaciers usually occur near their termini due to relatively large accumulation areas draining through narrow outlets. Estimates of ice thickness at the fronts of tidewater-terminating glaciers are combined with the velocity measurements to determine a regional dynamic discharge rate of between ∼17 Mt a−1 and ∼108 Mt a−1, with a mid-point estimate of ∼55 Mt a−1, revising downward previous approximations. These velocities can be used as inputs for glacier flow models, and provide a baseline dataset against which future changes in ice dynamics can be detected.

Changes in ice dynamics, elevation and mass discharge of Dinsmoor–Bombardier–Edgeworth glacier system, Antarctic Peninsula

The northern Antarctic Peninsula is one of the fastest changing regions on Earth. The disintegration of the Larsen-A Ice Shelf in 1995 caused tributary glaciers to adjust by speeding up, surface lowering, and overall increased ice-mass discharge. In this study, we investigate the temporal variation of these changes at the Dinsmoor–Bombardier–Edgeworth glacier system by analyzing dense time series from various spaceborne and airborne Earth observation missions. Precollapse ice shelf conditions and subsequent adjustments through 2014 were covered. Our results show a response of the glacier system some months after the breakup, reaching maximum surface velocities at the glacier front of up to 8.8 m/d in 1999 and a subsequent decrease to ∼1.5 m/d in 2014. Using a dense time series of interferometrically derived TanDEM-X digital elevation models and photogrammetric data, an exponential function was fitted for the decrease in surface elevation. Elevation changes in areas below 1000 m a.s.l. amounted to at least 130±15 m between 1995 and 2014, with change rates of ∼3.15 m/a between 2003 and 2008. Current change rates (2010–2014) are in the range of 1.7 m/a. Mass imbalances were computed with different scenarios of boundary conditions. The most plausible results amount to −40.7±3.9 Gt. The contribution to sea level rise was estimated to be 18.8±1.8 Gt, corresponding to a 0.052±0.005 mm sea level equivalent, for the period 1995–2014. Our analysis and scenario considerations revealed that major uncertainties still exist due to insufficiently accurate ice-thickness information. The second largest uncertainty in the computations was the glacier surface mass balance, which is still poorly known. Our time series analysis facilitates an improved comparison with GRACE data and as input to modeling of glacio-isostatic uplift in this region. The study contributed to a better understanding of how glacier systems adjust to ice shelf disintegration.