S. V. Popov

Bio: S. V. Popov is an academic researcher. The author has contributed to research in topics: Subglacial lake & Ice sheet. The author has an hindex of 11, co-authored 17 publications receiving 437 citations.

Distribution of marine ice beneath the Amery Ice Shelf

Abstract: We present a map of the marine ice accreted to the base of the Amery Ice Shelf (AIS), East Antarctica. This map is obtained by converting a Digital Elevation Model (DEM) of the AIS generated from satellite radar altimeter data to an ice thickness map, assuming hydrostatic equilibrium, and subtracting from that a second ice thickness map, derived from airborne radio-echo sounding (RES) measurements. The RES signal does not penetrate the marine ice, so the measurement is only to the meteoric-marine ice boundary, and therefore the difference between the two maps is the marine ice thickness. The marine ice is up to 190 m thick and accounts for about 9% of the shelf volume. It is concentrated in the northwest of the shelf, a result of the clockwise ocean circulation in the cavity below.

Redefinition of the Amery Ice Shelf, East Antarctica, grounding zone

Abstract: [1] New evidence is presented which shows that the Amery Ice Shelf, East Antarctica, extends ∼240 km upstream of the previously reported position. We combine a digital elevation model of the Amery Ice Shelf created from ERS-1 satellite radar altimetry with measured ice thicknesses and a simple density model in a hydrostatic (buoyancy) calculation to map the extent of the floating ice. This reveals that the ice is floating as far south as 73.2°S. The result is confirmed by static GPS measurements collected during three consecutive field campaigns on the Amery Ice Shelf where the vertical component of the GPS shows a clear tidal signal at 72.98°S. Other evidence for the grounding zone position comes from an analysis of satellite imagery, mass flux calculations, and ice radar data. The southward extension of the grounding line substantially alters the shape and dimensions of the ocean cavity beneath the ice shelf, which has implications for modeling studies of sub-ice shelf processes, such as basal melting and freezing, ocean circulation, and tides. The new grounding line position will also improve geophysical studies, where the computation of ocean tidal loading corrections is important for postglacial rebound estimates and correction of satellite altimetry measurements within the region.

Validation of satellite altimetry by kinematic GNSS in central East Antarctica

Abstract: . Ice-surface elevation profiles of more than 30 000 km in total length are derived from kinematic GNSS (GPS and the Russian GLONASS) observations on sledge convoy vehicles along traverses between Vostok Station and the East Antarctic coast. These profiles have accuracies between 4 and 9 cm. They are used to validate elevation data sets from both radar and laser satellite altimetry as well as four digital elevation models. A crossover analysis with three different processing versions of Envisat radar altimetry elevation profiles yields a clear preference for the relocation method over the direct method of slope correction and for threshold retrackers over functional fit algorithms. The validation of CryoSat-2 low-resolution mode and SARIn mode data sets documents the progress made from baseline B to C elevation products. ICESat laser altimetry data are demonstrated to be accurate to a few decimetres over a wide range of surface slopes. A crossover adjustment in the region of subglacial Lake Vostok combining ICESat elevation data with our GNSS profiles yields a new set of ICESat laser campaign biases and provides new, independent evidence for the stability of the ice-surface elevation above the lake. The evaluation of the digital elevation models reveals the benefits of combining laser and radar altimetry.

Forty-seven new subglacial lakes in the 0–110° E sector of East Antarctica

Abstract: During the summer field seasons of 1987-91, studies of central East Antarctica by airborne radio-echo sounding commenced. This scientific work continued in the 1990s in the Vostok Subglacial Lake area and along the traverse route from Mirny, and led to the discovery of 16 new subglacial water cavities in the areas of Domes Fuji and Argus and the Prince Charles Mountains. Twenty-nine subglacial water cavities were revealed in the area near Vostok, along with a feature we believe to be a subglacial river. Two subglacial lakes were discovered along the Mirny-Vostok traverse route. These are located 50 km north of Komsomolskaya station and under Pionerskaya station. We find high geothermal heat flux in the vicinity of the largest of the subglacial lakes, and suggest this may be due to their location over deep faults where additional mantle heat is available.

Precise analysis of ICESat altimetry data and assessment of the hydrostatic equilibrium for subglacial Lake Vostok, East Antarctica

Abstract: SUMMARY Based on the Ice, Cloud and Land Elevation Satellite (ICESat) laser altimetry data, the hydrostatic equilibrium (HE) condition for the subglacial Lake Vostok, East Antarctica, is evaluated. A digital elevation model (DEM) of the ice surface is derived by a regional crossover adjustment. The analysis of the DEM and its comparison with GPS derived ice-surface elevations and an ice-surface DEM based on radar altimetry data reveal an overall accuracy of better than ± 0.7 m for the lake area. The DEM is combined with an ice-thickness model and a regional geoid model to determine the deviation of the local ice-surface height from HE. For large parts of the lake, the ice sheet fulfils the HE. Our results reveal a strong positive deviation of about 10 m along the lake shoreline. In addition, positive deviations are found in the northern part of the lake which coincide with ice rumples detected by radio-echo sounding. In the southern part of the lake, we find a linear negative deviation (−4.0 m) which coincides with the convoy route from Vostok station to Mirny base. In addition to the DEM, relative biases for the ICESat laser operational periods are determined in the regional crossover adjustment.

Mass balance of the Antarctic ice sheet from 1992 to 2017.

Abstract: The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain.

Calving fluxes and basal melt rates of Antarctic ice shelves

Abstract: Iceberg calving has been assumed to be the dominant cause of mass loss for the Antarctic ice sheet, with previous estimates of the calving flux exceeding 2,000 gigatonnes per year1, 2. More recently, the importance of melting by the ocean has been demonstrated close to the grounding line and near the calving front3, 4, 5. So far, however, no study has reliably quantified the calving flux and the basal mass balance (the balance between accretion and ablation at the ice-shelf base) for the whole of Antarctica. The distribution of fresh water in the Southern Ocean and its partitioning between the liquid and solid phases is therefore poorly constrained. Here we estimate the mass balance components for all ice shelves in Antarctica, using satellite measurements of calving flux and grounding-line flux, modelled ice-shelf snow accumulation rates6 and a regional scaling that accounts for unsurveyed areas. We obtain a total calving flux of 1,321 ± 144 gigatonnes per year and a total basal mass balance of −1,454 ± 174 gigatonnes per year. This means that about half of the ice-sheet surface mass gain is lost through oceanic erosion before reaching the ice front, and the calving flux is about 34 per cent less than previous estimates derived from iceberg tracking1, 2, 7. In addition, the fraction of mass loss due to basal processes varies from about 10 to 90 per cent between ice shelves. We find a significant positive correlation between basal mass loss and surface elevation change for ice shelves experiencing surface lowering8 and enhanced discharge9. We suggest that basal mass loss is a valuable metric for predicting future ice-shelf vulnerability to oceanic forcing.

Elevation and elevation change of Greenland and Antarctica derived from CryoSat-2

Abstract: . This study focuses on the present-day surface elevation of the Greenland and Antarctic ice sheets. Based on 3 years of CryoSat-2 data acquisition we derived new elevation models (DEMs) as well as elevation change maps and volume change estimates for both ice sheets. Here we present the new DEMs and their corresponding error maps. The accuracy of the derived DEMs for Greenland and Antarctica is similar to those of previous DEMs obtained by satellite-based laser and radar altimeters. Comparisons with ICESat data show that 80% of the CryoSat-2 DEMs have an uncertainty of less than 3 m ± 15 m. The surface elevation change rates between January 2011 and January 2014 are presented for both ice sheets. We compared our results to elevation change rates obtained from ICESat data covering the time period from 2003 to 2009. The comparison reveals that in West Antarctica the volume loss has increased by a factor of 3. It also shows an anomalous thickening in Dronning Maud Land, East Antarctica which represents a known large-scale accumulation event. This anomaly partly compensates for the observed increased volume loss of the Antarctic Peninsula and West Antarctica. For Greenland we find a volume loss increased by a factor of 2.5 compared to the ICESat period with large negative elevation changes concentrated at the west and southeast coasts. The combined volume change of Greenland and Antarctica for the observation period is estimated to be −503 ± 107 km3 yr−1. Greenland contributes nearly 75% to the total volume change with −375 ± 24 km3 yr−1.

A new tide model for the Antarctic ice shelves and seas

Abstract: We describe a new tide model for the seas surrounding Antarctica, including the ocean cavities under the floating ice shelves. The model uses data assimilation to improve its fit to available data. Typical peak-to-peak tide ranges on ice shelves are 1-2 m but can exceed 3 m for the Filchner-Ronne and Larsen Ice Shelves in the Weddell Sea. Spring tidal ranges are about twice these values. Model performance is judged relative to the ~5-10 cm accuracy that is needed to fully utilize ice shelf height data that will be collected with the Geoscience Laser Altimeter System, scheduled to be launched on the Ice, Cloud and land Elevation Satellite in late 2002. The model does not yet achieve this level of accuracy except very near the few high quality tidal records that have been assimilated into the model. Some improvement in predictive skill is expected from increased sophistication of model physics, but we also require better definition of ice shelf grounding lines and more accurate water column thickness data in shelf seas and under the ice shelves. Long-duration tide measurements (bottom pressure gauge or GPS) in critical data-sparse areas, particularly near and on the Filchner-Ronne and Ross ice shelves and Pine Island Bay, are required to improve the performance of the data assimilation model.

An inventory of active subglacial lakes in Antarctica detected by ICESat (2003-2008)

Abstract: Through the detection of surface deformation in response to water movement, recent satellite studies have demonstrated the existence of subglacial lakes in Antarctica that fill and drain on timescales of months to years. These studies, however, were confined to specific regions of the ice sheet. Here we present the first comprehensive study of these 'active' lakes for the Antarctic ice sheet north of 868 S, based on 4.5 years (2003-08) of NASA's Ice, Cloud and land Elevation Satellite (ICESat) laser altimeter data. Our analysis has detected 124 lakes that were active during this period, and we estimate volume changes for each lake. The ICESat-detected lakes are prevalent in coastal Antarctica, and are present under most of the largest ice-stream catchments. Lakes sometimes appear to transfer water from one to another, but also often exchange water with distributed sources undetectable by ICESat, suggesting that the lakes may provide water to or withdraw water from the hydrologic systems that lubricate glacier flow. Thus, these reservoirs may contribute pulses of water to produce rapid temporal changes in glacier speeds, but also may withdraw water at other times to slow flow.