Central Ice Sheet Research Articles

СОСТОЯНИЕ АДРЕНОКОРТИКАЛЬНОЙ И СИМПАТОАДРЕНАЛОВОЙ СИСТЕМ, СУБСТРАТОВ ЭНЕРГЕТИЧЕСКОГО ОБМЕНА В КРОВИ ЧЕЛОВЕКА ПРИ ГОДИЧНОМ ПРЕБЫВАНИИ В УСЛОВИЯХ ГИПОБАРИЧЕСКОЙ ГИПОКСИИ, ГИПОКИНЕЗИИ И ИЗОЛЯЦИИ

Year-long life on Antarctic scientific station Vostok was characterized by exposure to the physiologically important factors including hypobaric hypoxia (Р = 460 mm Hg) due to the location on the Central Ice Sheet, hypokinesia due to staying indoor most of the time because of very low temperatures outdoors, physical and social isolation from the world. The paper attempts to define which of these factors determined the human body stress-reaction and energy metabolism. Venous plasma samples were periodically gathered for analysis from 16 members of the 13th Soviet Antarctic expedition to the station Vostok in 1968. Members of the expedition were divided into 2 groups. One group was experimental, i.e. intermittently consumed anti-asthenia amino acid and vitamin supplements and psychoactive drugs, and the other was the placebo control. The investigation showed that in the course of the year-long existence in the extreme environment the averaged levels of 11-oxicorticosteroids and adrenergic compounds were elevated while the noradrenergic levels were at the bottom margins of their normal ranges. Averaged values of blood glucose and total cholesterol were well within the range of normal variations. Anti-asthenia supplements mitigated the chronic stress and did not disturb energy metabolism.

Greenland plateau jets

The high ice-covered topography of Greenland represents a significant barrier to atmospheric flow and, as a direct and indirect result, it plays a crucial role in the coupled climate system. The wind field over Greenland is important in diagnosing regional weather and climate, thereby providing information on the mass balance of the ice sheet as well as assisting in the interpretation of ice core data. Here, we identify a number of hitherto unrecognised features of the three-dimensional wind field over Greenland; including a 2500-km-long jet along the central ice sheet's western margin that extends from the surface into the middle-troposphere, as well as a similar but smaller scale and less intense feature along its eastern margin. We refer to these features as Greenland Plateau Jets. The jets are coupled to the downslope katabatic flow and we argue that they are maintained by the zonal temperature gradients associated with the strong temperature inversion over the central ice sheet. Their importance for Greenland's regional climate is discussed.

Present and future near-surface wind climate of Greenland from high resolution regional climate modelling

The present and twenty-first century near-surface wind climate of Greenland is presented using output from the regional atmospheric climate model RACMO2. The modelled wind variability and wind distribution compare favourably to observations from three automatic weather stations in the ablation zone of southwest Greenland. The Weibull shape parameter is used to classify the wind climate. High values (κ > 4) are found in northern Greenland, indicative of uniform winds and a dominant katabatic forcing, while lower values (κ < 3) are found over the ocean and southern Greenland, where the synoptic forcing dominates. Very high values of the shape parameter are found over concave topography where confluence strengthens the katabatic circulation, while very low values are found in a narrow band along the coast due to barrier winds. To simulate the future (2081–2098) wind climate RACMO2 was forced with the HadGEM2-ES general circulation model using a scenario of mid-range radiative forcing of +4.5 W m−2 by 2100. For the future simulated climate, the near-surface potential temperature deficit reduces in all seasons in regions where the surface temperature is below the freezing point, indicating a reduction in strength of the near-surface temperature inversion layer. This leads to a wind speed reduction over the central ice sheet where katabatic forcing dominates, and a wind speed increase over steep coastal topography due to counteracting effects of thermal and katabatic forcing. Thermally forced winds over the seasonally sea ice covered region of the Greenland Sea are reduced by up to 2.5 m s−1.

An advancing glacier in a recessive ice regime: Berlingske Bræ, North-West Greenland

Greenland is receiving unprecedented international attention, both in scientific and political circles. Characterised by a central ice sheet up to 3.4 km thick (Inland Ice), numerous ice caps and hundreds of outlet glaciers debouching into the surrounding oceans, Greenland supports the second largest ice mass in the world. Analysis of glacier movements, melt rates and ice loss to the sea, provide data with which to assess mass balance changes and thereby predict global sealevel rise. Thus Greenland plays a central role in the current worldwide debate on climate change. Present-day dynamic ice loss is invariably advertised by the fast moving glaciers of western Greenland with their spectacular calf ice production, such as the ice streams around Disko Bugt reviewed by Weidick &amp; Bennike (2007). This tends to overshadow ice stability and expansion seen in the form of stationary and advancing glaciers elsewhere in Greenland (MODIS 2009). While the seawards acceleration of glacier flow and retreat in frontal positions can be readily attributed to a shift in atmospheric and oceanic conditions (global warming), the same explanation can hardly be used for glaciers with contrasting movement histories.

The bedrock geology under the Inland Ice: the next major challenge for Greenland mapping

Geological maps are of vital importance for documenting and advancing geological knowledge and they are a prerequisite for any meaningful evaluation of economic resources. In Greenland, mapping is taking place on the mainland – that for two centuries has been the traditional exploration target – and offshore, where only in the last decades has hydrocarbon exploration moved to the continental shelves. Greenland with its 2 166 000 km2 is the largest island in the world. However, the land is overwhelmed by ice. A central ice sheet – the Inland Ice – blankets some 81% of the country reducing rock outcrop to a coastal fringe 0 to 300 km wide (Fig. 1). The continental shelves comprise a little more than twice the area of this fringe, c. 830 000 km2. This preamble serves to emphasise that Greenland’s three physiographic units – exposed fringe, offshore and Inland Ice – are of very different size and that mapping has focused on the smallest acreage. Piecing together the composition of the largest, and hitherto unexplored, unit constitutes the next chapter of Greenland mapping.

Antarctic ecosystems as models for extraterrestrial surface habitats

Surface habitats in Antarctic deserts are near the limits of life on Earth and resemble those hypothesized for early Mars. Cyanobacteria dominate the transient riverbeds, stromatolitic sediments in ice-covered lakes, and endolithic communities in translucent rock. There is still no direct evidence of photosynthetic life on early Mars, but cyanobacteria are amongst the earliest microbes detectable in the fossil record for analogous habitats on Earth. Key biomolecules persist in Antarctic microbial habitats, even after extinction by excessive low temperatures, desiccation and UV-B stress within the Ozone Hole. Pigments (or their fossil residues), such as chlorophyll and the UV-protectants scytonemin, carotene and quinones, are good biomarkers. To show not only their presence but also their micro-spatial distribution in situ, we describe the use of FT–Raman spectroscopy with 1064 nm excitation to avoid autofluorescence from the pigments. We report not only the diversity of biomolecules that we have diagnosed from their unique Raman spectra of Antarctic cyanobacterial communities, but also their functional stratification in endolithic communities. Our analyses of Antarctic habitats show the potential of this remote, non-intrusive technique to probe for buried biomolecules on future Mars missions and in Antarctic Lake Vostok, >4 km beneath the Central Ice Sheet, with implications for the putative analogous sub-ice ocean on Europa.

Comparison of retracking algorithms for ERS-1 altimeter data over Greenland

Six months of processed ERS-1 full waveform altimetry data have been used to study the ERS-1 altimeter performance over the Greenland ice sheet. Surface profiles from repeated ground tracks have been studied to explain the character of the data and the performance of several waveform processing techniques. A cross-over analysis has been performed to assess the repeatability of retracked data. The RMS of ocean-mode cross-over differences is found to be around 0.5 m for most parts of the central ice sheet, with values larger than 2 m for areas with large variations in surface height. For these areas the ice mode cross-over differences are smaller. Average waveforms from the central part of the ice sheet show the presence of substantial sub-surface volume scattering.

Antarctic aerosols: A review

The vast ice sheet of Antarctica is isolated geographically but not meteorologically from the rest of the planet. Tropospheric aerosols in or near the accumulation mode size, around a half micron diameter, reside in the atmosphere for tens of days and teleconnect Antarctica with other regions by transport that reaches planetary scales of distances. The aerosol on the ice sheet, therefore, at any time and place represents “memory modules” of events that took place at regions separated from Antarctica by tens of thousands of kilometers. Scientific attention to this collective aerosol system provides insight into long‐range atmospheric transport. Investigations of particles in the ultraclean air over Antarctica were slow to get going mainly because of a failure to recognize the possibility of semiglobal transport of “dust”; as a result, this field is very young, having gone through its “romantic period” of exploratory studies in the late 1960s and entered into a time of synthesis and paradigm building only in the mid‐1970s. An important recent discovery is that the aerosol number concentration (the condensation nuclei (CN)) over this distant ice sheet undergoes a regular, methodical and predictable seasonal variation, nearly disappearing around winter solstice but being relatively robust (i.e., comparable to what one finds over mid‐oceans) in summer. A weakened seasonal modulation of CN is found at coastal sites. Circumstantial evidence indicates that the CN over the ice are produced from gas photolytically. Thus the tiniest particles over Antarctica are products of a slow “chemical” conversion within the atmosphere itself. A major discovery with numerous possible deep geobiological ramifications is that the aerosol over the ice sheet is by mass 70–90% sulfate, in the molecular form of hydrated droplets of sulfuric acid, except during transient events of a few days duration when atmospheric transport forces warm, moist air from the oceans into the interior continental regions. These events are most frequent in late winter‐early spring, accompanying the breakdown of the circumpolar vortex. These “sodium storms” transport large quantities of sea salt to the central ice sheet sporadically. Chemical studies of the submicron ice cap aerosols indicate that there is a uniquely winter and uniquely summer “crustal,” insoluble aerosol that represents &lt;5% of aerosol mass but which has provided an interesting long‐term permanent record of itself going back 2 × 105 years in the ice. In terms of aerosol mass, the aerosol is composed of crustal products (&lt;5%), transported sea‐salt residues (highly variable but averaging ∼ 10%), Ni‐rich meteoric material, and anomalously enriched material with an unknown origin. Most of the Antarctic aerosol, however, is the “natural acid sulfate aerosol” apparently deriving from biological processes taking place in the surrounding oceans.