East Dronning Maud Land Research Articles

Estimation of Net Radiation Flux of Antarctic Ice Sheet in East Dronning Maud Land, Antarctica, During Clear Sky Days Using Remote Sensing and Meteorological Data

In the present paper, incoming shortwave radiation flux, net shortwave radiation flux, net longwave radiation flux, and net radiation flux have been estimated at 1-km spatial scale for the ice sheet in East Dronning Maud Land, Antarctica. Terra-MODIS (Moderate Resolution Imaging Spectroradiometer) products (i.e., land and atmospheric data products) have been used to estimate net radiation flux during few clear sky days of the years 2007, 2008, 2009, and 2010. Estimated surface energy fluxes using MODIS products have been evaluated using in situ recorded values of energy fluxes. In situ data of the surface energy fluxes and meteorological parameters have been collected using automatic weather stations (AWS) on ice sheet at two locations near the Indian Research Station “Maitri.” Net radiation flux has been estimated for the study area from net shortwave radiation flux and net longwave radiation flux maps. Bias, correlation, and root mean square error (RMSE) between AWS-recorded and MODIS-derived radiation fluxes have been observed as − 23 W m−2, 0.91 and 61 W m−2 for net shortwave radiation flux and − 21.3 W m−2, 0.93 and 64 W m−2 for net radiation flux, respectively. The study highlights the validation of some of the MODIS products and MODIS-derived energy fluxes in Antarctica. Spatial and temporal variations of radiative energy fluxes have also been investigated in the study area.

Measurements of Net Subsurface Heat Flux in Snow and Ice Media in Dronning Maud Land, Antarctica

Abstract: Sub-surface heat flux plays an important role in the energy balance of snow cover, glaciers and ice sheets, and varies with the density of snow/ice media. In this paper, we report experimental observations of the sub-surface heat flux conducted in different snow and ice media in Antarctica. Experiments were conducted on low density fresh snowpack, wind compacted high density snowpack, and blue ice area in east Dronning Maud Land, Antarctica, in a radius of 10 km from Indian research station Maitri (70°46'03.98" S and 11°41'40.72" E). Direct measurements of net subsurface heat flux were carried out using an experimental setup consisting of heat flux plates. Two heat flux plates along with two temperature sensors were placed horizontally inside the snowpack / ice sheet at a depth of approximately 10 cm from the surface during summer season between December 2011and February 2012. The mean diurnal net subsurface heat fluxes for low density snow (location 1), high density wind compacted snow (location 2), and blue ice area (location 3) observed were 7.36±9.39 W m-2, -0.12±7.6 W m-2 and 3.20±13.32 W m-2, respectively, during the measurements periods. The amplitudes of the mean diurnal variations of net sub-surface heat flux were 14.23 W m-2, 11.42 W m-2 and 18.55 W m-2 at location 1, location 2 and location 3, respectively. Mean net sub-surface heat flux was observed to be comparatively lower for wind compacted high density snow.

Combined use of InSAR and GLAS data to produce an accurate DEM of the Antarctic ice sheet: Example from the Breivika–Asuka station area

Surface elevation data for the Breivika–Asuka Station area, East Dronning Maud Land, Antarctica, obtained during ground surveys undertaken in 1987 were compared with elevation data measured by the Geoscience Laser Altimeter System (GLAS) onboard the Ice, Cloud, and land Elevation Satellite (ICESat) in 2003. The two sets of measurements were consistent within ±12.4 m for an elevation range from 300 to 1000 m. We produced an interferometric synthetic aperture radar (InSAR) digital elevation model (DEM) with 50 m grid spacing and InSAR DEM heights were corrected using GLAS heights as ground-truth data. The height differences are assumed to have a quadratic function of rectangular polar stereographic coordinates with six coefficients, and the most probable estimate of the correction parameter set was calculated using a least squares method. Before correction, the root-mean-square (rms) height error was ±284 m; after correction, the associated error was reduced to ±22.3 m, where the absolute error in the horizontal coordinates (grids) was ±230 m. The resultant InSAR DEM height error is twice as large as the GLAS DEM height error; however, the accuracy of the resultant InSAR DEM is reasonable when we consider the limitations of single baseline InSAR and the steep slopes (range in elevation: 1000 m) within the ice sheet region. An InSAR DEM with high spatial resolution and 2 m relative accuracy in terms of yearly change is useful for monitoring ice volume (mass) change by a superconducting gravimeter.

Total solar eclipse over Antarctica on 23 November 2003 and its effects on the atmosphere and snow near the ice sheet surface at Dome Fuji

The Moon cast a long shadow over Antarctica on 23 November 2003 in a total solar eclipse. The eclipse was observed at Dome Fuji Station, located at the highest point of East Dronning Maud Land, Antarctica, and lasted 1 h 41 min 37 s in a cloudless condition, during which the Sun was completely obscured for 1 min 43 s. This was the first total solar eclipse to be observed in the Antarctic ice sheet. During the eclipse at Dome Fuji, the air temperature at 1.5 m above the snow surface and the subsurface snow temperature decreased by 3.0 K and 1.8 K, respectively. Estimated surface snow temperatures decreased by 4.6 K. Atmospheric pressure and wind direction did not change, but the wind speed possibly decreased by 0.3 m/s with decreasing air temperature; natural variations in wind speed before and after the eclipse made it difficult to identify a true effect of the solar eclipse. Variations of energy components (net shortwave and longwave radiations, sensible and latent heat fluxes, and geothermal heat) during the eclipse were investigated. The total loss of global solar radiation during the eclipse was 0.60 MJ m−2, equaling 1.6% of the total daily global solar radiation. Regional effects of the eclipse due to a reduction of global solar radiation for air temperature and snow temperature ranged from 0.015 to 0.020 K (W m−2)−1. We additionally examined the relation between eclipse obscuration (the fraction of the Sun's surface area occulted by the Moon) and the reduction of global solar radiation from the first to second contacts. The eclipse was also observed from space by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard NASA's Terra and Aqua satellites. The observational results of this study will contribute to detailed model calculations for clarifying the meteorological effects of eclipses.

Accumulation variability over a small area in east Dronning Maud Land, Antarctica, as determined from shallow firn cores and snow pits: some implications for ice-core records

AbstractWe investigate and quantify the variability of snow accumulation rate around a medium-depth firn core (160 m) drilled in east Dronning Maud Land, Antarctica (75°00′ S, 15°00’ E; 3470 m h.a.e. (ellipsoidal height)). We present accumulation data from five snow pits and five shallow (20 m) firn cores distributed within a 3.5–7 km distance, retrieved during the 2000/01 Nordic EPICA (European Project for Ice Coring in Antarctica) traverse. Snow accumulation rates estimated for shorter periods show higher spatial variance than for longer periods. Accumulation variability as recorded from the firn cores and snow pits cannot explain all the variation in the ion and isotope time series; other depositional and post-depositional processes need to be accounted for. Through simple statistical analysis we show that there are differences in sensitivity to these processes between the analyzed species. Oxygen isotopes and sulphate are more conservative in their post-depositional behaviour than the more volatile acids, such as nitrate and to some degree chloride and methanesulphonic acid. We discuss the possible causes for the accumulation variability and the implications for the interpretation of ice-core records.

Thermal structure of Dome Fuji and east Dronning Maud Land, Antarctica, simulated by a three-dimensional ice-sheet model

AbstractThree-dimensional structures of temperature focused on Dome Fuji and east Dronning Maud Land, Antarctica, simulated in a three-dimensional shallow ice model, are reported. With a geothermal heat flux of 54.6 mWm–2, as used in several modelling studies of the Antarctic ice sheet, and an enhancement factor of 1.3, which is smaller than in previous studies, the model result taking into account the glacial cycles is in good agreement with the borehole temperature and surface topography at Dome Fuji. The basal temperature at Dome Fuji must be at or very close to the pressure-melting point. The simulated amplitude of basal temperature through glacial/interglacial cycles is <1 K.

Lead-210 profile in firn layer over Antarctic ice sheet and its relation to the snow accumulation environment

Vertical distributions of 210Pb in surface firn were obtained at five locations in east Dronning Maud Land, Antarctica. The distributions obtained in the inland high-plateau region are well described by the theoretical radioactive decay curve. On the other hand, the distributions obtained in the katabatic wind region have significant fluctuations including intervals where higher activity is found below layers with lower activity. We examined the relationship between the fluctuation of the 210Pb profile and the temporal variation of the snow accumulation rate obtained by the snow stake method, and found a clear negative correlation between them. This result suggests that the fluctuation of the 210Pb profile in the firn layer is closely related to the environment in the ice sheet surface, i.e. the extent of erosion—redistribution of snow. The measurement of the 210Pb distribution in the ice sheet will be useful as an indicator of the surface stability in the Antarctic ice sheet.

Distribution of sea salt components in snow cover along the traverse route from the coast to Dome Fuji station 1000 km inland at east Dronning Maud Land, Antarctica

Distribution of sea salt components in snow cover along the traverse route from the coast to Dome Fuji station 1000 km inland at east Dronning Maud Land, Antarctica

Annual-layer determinations and 167 year records of past climate of H72 ice core in east Dronning Maud Land, Antarctica

AbstractTo determine annual layers for reconstructing the past environment at annual resolution from ice cores, we employed snow-stake data back to 1972, tritium content, solid electrical conductivity measurements (ECM) and stratigraphic properties for the 73m ice core at the H72 site, east Dronning Maud Land, Antarctica. the average annual surface mass balance at H72 is 307 mma–1w.e. during the last 27 years from continuous accumulation data, 317 mma–1 w.e. according to the densification model and 311 mma–1 w.e. according to the average surface mass balance for 167 years based on annual-layer counting. the ECM age is closely coincident with tritium age, and corresponds with the snow-stake record back to AD 1972 from the surface to 15 m depth. the H72 ice core is dated as AD 1831by ECMat 73.16 mdepth.The time series of yearly surface mass balance at H72 shows an almost constant 311 mm a–1 w.e. for the last 167 years. the oxygen-isotope records indicate a significant trend to lower values, with negative gradient of 1.7% (100 years)–1.

Distribution of sea salt components in snow cover along the traverse route from the coast to Dome Fuji station 1000 km inland at east Dronning Maud Land, Antarctica

We show and discuss the results of the regional distribution of Cl− and Na+ concentrations in snow cover along the study route from the coast to Dome Fuji station, 1000 km inland, in east Dronning Maud Land, Antarctica. The concentrations of Cl− and Na+ at the coast exponentially decreased with distance from the coast up to 200 km inland. Between 200–1000 km inland, the concentrations of Na+ were nearly constant. On the other hand, the concentrations of Cl− increased with distance beyond 750 km inland. Furthermore, the contribution factors between Cl− and Na+ decreased and the Cl−/Na+ ratio and the nssCl−/Cl− ratio increased toward the interior of the continent. These results indicate that sea salt aerosols are transported from the coastal region toward the inland region of the Antarctic continent, and that a source of Cl− other than sea salt exists in the inland plateau of Antarctica.

A ground-based, multi-frequency ice-penetrating radar system

AbstractTo better understand how ice sheets respond to climate, we designed a new multi-frequency ice-penetrating radar system to investigate subsurface structures of ice sheets. The system is mounted on a single platform and handled by a single operator. Three radio frequencies, 30,60 and 179 MHz, were used. An underlying principle of these multi-frequency observations is that the lower frequencies are more sensitive to electrical conductivity changes, whereas the higher frequencies are more sensitive to dielectric permittivity fluctuations in the ice. The system is composed of three single-frequency pulse radars, a trigger-controller unit and a data-acquisition unit. The trigger controller is the key component of this system. It switches transmitters on at different timings to prevent mixing of signals among the three radars. The timing difference was set as 50 μs, which is equivalent to the two-way travel time for radio waves reflecting from 4250m below the surface. A field test was done along a 2000 km long traverse line in east Dronning Maud Land, Antarctica. The multi-frequency system successfully acquired data that are equivalent in quality to our earlier single-frequency measurements along the same traverse line. The details of the system and preliminary data are described.

Preliminary investigation of palaeoclimate signals recorded in the ice core from Dome Fuji station, east Dronning Maud Land, Antarctica

ABSTRACT An ice core to 2503.52 m depth was drilled during 1995 and 1996 at 77°19′01″S, 39°42′12″ E (3810 m a.s.l.), at the summit of Dome Fuji, East Antarctica. Climatic and environmental conditions were observed at the coring site throughout the 2 years of wintering operation. Meteorological and glaciological observations made clear the present surface processes of mass balance. The chemistry of the surface snow layers was observed for investigation of the atmospheric environment reflected in snow deposits. Core analyses have been carried out in Japan. Permeability and density measurements show that air bubbles are completely closed off by densification processes at about 98 m depth. The vertical profile of δ 18O suggests that the core covers two warm stages and one cold stage from the surface down to 1800 m depth. The transition from the cold to the warm period affects the vertical distribution of ice-crystal size. The chemical constituents in the ice core show large differences between warm and cold periods. A depth–age relationship is presented and a study made of palaeoclimatic and core signals.

Deep ice-core drilling at Dome Fuji and glaciological studies in east Dronning Maud Land, Antarctica

The Dome Fuji Project is a comprehensive study of present and past glaeiological/climatological features of the Antarctic ice sheet in east Dronning Maud Land. Field observations on a 100U km traverse route from the coast to Dome Fuji slum changes in various glaciological parameters with surface elevation and distance from the coast. Deep ice-core drilling at Dome Fuji was started in August 1995 and reached a depth of 2503.52 m in December 1996. in situ core analyses revealed 25 visible tephra layers and a number of distinct cloudy bands in the ice.

Surface mass balance in east Dronning Maud Land, Antarctica, observed by Japanese Antarctic Research Expeditions

The surface mass balance in east Dronning Maud Land has been observed mainlvbv means of the snow-stake method. The surface mass balance generallv decreased with distance from the coast; from more than 250 mm a−1 in the coastal region to less than 50 mm a−1 in the inland region higher than 3500 m in altitude. At Mizuho Station (2230 m a.s.l.). the sublimation was about 50 mm a−1. precipitation was between 140 and 260 mm a−1, and the loss from the surface by theredistribution was estimated to be about 100 mm a−1, which agrees with the surface mass balance estimated as 70 mm a−1 from the grain-growth rate. Around the mountainous area, the balance was small or in some cases negative, where a bare-ice field has developed. In the inland area, 3000– 3200 m a.s.l..the surface mass balance was less than 50 mm a−1, i.e. lower than in the surrounding areas. This low mass-balance area can be explained bv redistribution by the drifting snow. The whole mass input in five drainage basins with a total area of 620 × 103 km2 is 61.2Gton a−1 and the mean surface mass balance is 99 mm a−1.

Studies on microparticles contained in medium-depth ice cores retrieved from east Dronning Maud Land, Antarctica

SEM observations of microparticles in ice-core samples retrieved by the Japanese Antarctic Research Expedition in east Dronning Maud Land have been carried out since 1987. Morphology and elemental composition by EDS of many microparticles taken from various depths of the 700 m Mizuho ice core were compared with each other and with those of stratospheric microparticles in NASA Cosmic Dust Catalogs and microparticles hitherto found in deep ice cores retrieved in Antarctica. Number concentrations of microparticles were measured on all samples throughout the 700 m Mizuho ice core. Remarkable fluctuations found in the depth profile of the concentration seem to coincide with cold climates indicated by δ18O of the same core. Compositional analysis of volcanic ash at a depth of 500.7 m in the Mizuho ice core, dated at approximately 6000 years BP, indicates that the ash originated from the South Sandwich Islands.

Studies on microparticles contained in medium-depth ice cores retrieved from east Dronning Maud Land, Antarctica

SEM observations of microparticles in ice-core samples retrieved by the Japanese Antarctic Research Expedition in east Dronning Maud Land have been carried out since 1987. Morphology and elemental composition by EDS of many microparticles taken from various depths of the 700 m Mizuho ice core were compared with each other and with those of stratospheric microparticles in NASA Cosmic Dust Catalogs and microparticles hitherto found in deep ice cores retrieved in Antarctica. Number concentrations of microparticles were measured on all samples throughout the 700 m Mizuho ice core. Remarkable fluctuations found in the depth profile of the concentration seem to coincide with cold climates indicated by δ18O of the same core. Compositional analysis of volcanic ash at a depth of 500.7 m in the Mizuho ice core, dated at approximately 6000 years BP, indicates that the ash originated from the South Sandwich Islands.

Surface mass balance in east Dronning Maud Land, Antarctica, observed by Japanese Antarctic Research Expeditions

The surface mass balance in east Dronning Maud Land has been observed mainlvbv means of the snow-stake method. The surface mass balance generallv decreased with distance from the coast; from more than 250 mm a−1in the coastal region to less than 50 mm a−1in the inland region higher than 3500 m in altitude. At Mizuho Station (2230 m a.s.l.). the sublimation was about 50 mm a−1. precipitation was between 140 and 260 mm a−1, and the loss from the surface by theredistribution was estimated to be about 100 mm a−1, which agrees with the surface mass balance estimated as 70 mm a−1from the grain-growth rate. Around the mountainous area, the balance was small or in some cases negative, where a bare-ice field has developed. In the inland area, 3000– 3200 m a.s.l..the surface mass balance was less than 50 mm a−1, i.e. lower than in the surrounding areas. This low mass-balance area can be explained bv redistribution by the drifting snow. The whole mass input in five drainage basins with a total area of 620 × 103km2is 61.2Gton a−1and the mean surface mass balance is 99 mm a−1.

Studies on microparticles contained in medium-depth ice cores retrieved from east Dronning Maud Land, Antarctica

SEM observations of microparticles in ice-core samples retrieved by the Japanese Antarctic Research Expedition in east Dronning Maud Land have been carried out since 1987. Morphology and elemental composition by EDS of many microparticles taken from various depths of the 700 m Mizuho ice core were compared with each other and with those of stratospheric microparticles in NASA Cosmic Dust Catalogs and microparticles hitherto found in deep ice cores retrieved in Antarctica. Number concentrations of microparticles were measured on all samples throughout the 700 m Mizuho ice core. Remarkable fluctuations found in the depth profile of the concentration seem to coincide with cold climates indicated by δ18O of the same core. Compositional analysis of volcanic ash at a depth of 500.7 m in the Mizuho ice core, dated at approximately 6000 years BP, indicates that the ash originated from the South Sandwich Islands.

Seasonal variations of major ionic concentration levels in drifting-snow samples obtained from east Dronning Maud Land, East Antarctica

Drifting-snow samples were collected at Mizuho Station (74°42' S, 44°20' E, 2230 m a.s.1.) from February to October 1986 and along traverse routes in east Dronning Maud Land (1800-3000 m a.s.1.), East Antarctica, from October 1986 to January 1987. The typical sampling interval was about once a week but two sets of intensive sampling were made at the end of February and November at between 2 h and 1 d intervalsMeasurements for CI-, NO3,SO42and Na+ were made on the drifting-snow samples by ion chromatography. Oxygen-isotope ratios were .also measured .on the samples. Concentrations levels ofNO3-and SO4-show distinctive seasonal variations: high in summer (4.6 neq g-1 for NO3and 3.3 neq g1 for SO42) and low in winter during mid-March to mid-November(1.0 neq g1 for NO3 and 0.5 neq g1 for SO42). Results obtained at Mizuho Station show that the transition from the summer high values to winter low values takes about 20 d for NO3 and SO42-.The variations in Cl and Na+ concentration levels are small in both autumn and spring (averages are about 1 neq g-l) with greater variability throughout the rest of the year. The intensive sampling data set shows that there is considerable variability within a day with NO3 and SO42-concentration levels up to about a factor of 4 associated with a 10%0 change in 3180 ratios.

Seasonal variations of major ionic concentration levels in drifting-snow samples obtained from east Dronning Maud Land, East Antarctica

Drifting-snow samples were collected at Mizuho Station (74°42' S, 44°20' E, 2230 m a.s.1.) from February to October 1986 and along traverse routes in east Dronning Maud Land (1800-3000 m a.s.1.), East Antarctica, from October 1986 to January 1987. The typical sampling interval was about once a week but two sets of intensive sampling were made at the end of February and November at between 2 h and 1 d intervalsMeasurements for CI-, NO3,SO42and Na+ were made on the drifting-snow samples by ion chromatography. Oxygen-isotope ratios were .also measured .on the samples. Concentrations levels ofNO3-and SO4-show distinctive seasonal variations: high in summer (4.6 neq g-1 for NO3 and 3.3 neq g1 for SO42) and low in winter during mid-March to mid-November(1.0 neq g1 for NO3 and 0.5 neq g1 for SO42). Results obtained at Mizuho Station show that the transition from the summer high values to winter low values takes about 20 d for NO3 and SO42-.The variations in Cl and Na+ concentration levels are small in both autumn and spring (averages are about 1 neq g-l) with greater variability throughout the rest of the year. The intensive sampling data set shows that there is considerable variability within a day with NO3 and SO42- concentration levels up to about a factor of 4 associated with a 10%0 change in 3180 ratios.