Circulation and melting beneath the ross ice shelf

Thermohaline observations in the water column beneath the Ross Ice Shelf and along its terminal face show significant vertical stratification, active horizontal circulation, and net melting at the ice shelf base. Heat is supplied by seawater that moves southward beneath the ice shelf from a central warm core and from a western region of high salinity. The near-freezing Ice Shelf Water produced flows northward into the Ross Sea.     

Core drilling through the ross ice shelf (antarctica) confirmed Basal freezing

New techniques that have been used to obtain a continuous ice core through the whole 416-meter thickness of the Ross Ice Shelf at Camp J-9 have demonstrated that the bottom 6 meters of the ice shelf consists of sea ice. The rate of basal freezing that is forming this ice is estimated by different methods to be 2 centimeters of ice per year. The sea ice is composed of large vertical crystals, which form the waffle-like lower boundary of the shelf. A distinct alignment of the crystals throughout the sea ice layer suggests the presence of persistent long-term currents beneath the ice shelf.     

Miocene glaciomarine sediments from beneath the southern ross ice shelf, antarctica

Glaciomarine sediments with middle Miocene microfaunal assemblages are exposed at the sea floor below the southern Ross Ice Shelf. Plio-Pleistocene sediments are not present. Post-Miocene glacial sediments may have been deposited but removed by relatively recent ice shelf grounding. A meager Recent microfauna is present in some core tops.     

Synchronous climate changes in antarctica and the north atlantic

Central Greenland ice cores provide evidence of abrupt changes in climate over the past 100,000 years. Many of these changes have also been identified in sedimentary and geochemical signatures in deep-sea sediment cores from the North Atlantic, confirming the link between millennial-scale climate variability and ocean thermohaline circulation. It is shown here that two of the most prominent North Atlantic events-the rapid warming that marks the end of the last glacial period and the Bolling/Allerod-Younger Dryas oscillation-are also recorded in an ice core from Taylor Dome, in the western Ross Sea sector of Antarctica. This result contrasts with evidence from ice cores in other regions of Antarctica, which show an asynchronous response between the Northern and Southern Hemispheres.     

Changes in the west antarctic ice sheet

The portion of the West Antarctic ice sheet that flows into the Ross Sea is thinning in some places and thickening in others. These changes are not caused by any current climatic change, but by the combination of a delayed response to the end of the last global glacial cycle and an internal instability. The near-future impact of the ice sheet on global sea level is largely due to processes internal to the movement of the ice sheet, and not so much to the threat of a possible greenhouse warming. Thus the near-term future of the ice sheet is already determined. However, too little of the ice sheet has been surveyed to predict its overall future behavior.     

Tritium and carbon-14 distributions in seawater from under the ross ice shelf project ice hole

The tritium and carbon-14 activities of seawater samples collected from 22 to 200 meters below the ice at the Ross Ice Shelf Project ice hole are reported. The tritium results show that the waters below the ice have exchanged with Ross Sea water since the advent of nuclear testing. The carbon-14 results indicate that waters in the upper layer exchange in time periods of less than 6 years. Measurements of these isotopes in seawater under the Ross Ice Shelf in McMurdo Sound show that this water has a different history.     

Large and rapid melt-induced velocity changes in the ablation zone of the Greenland Ice Sheet

Continuous Global Positioning System observations reveal rapid and large ice velocity fluctuations in the western ablation zone of the Greenland Ice Sheet. Within days, ice velocity reacts to increased meltwater production and increases by a factor of 4. Such a response is much stronger and much faster than previously reported. Over a longer period of 17 years, annual ice velocities have decreased slightly, which suggests that the englacial hydraulic system adjusts constantly to the variable meltwater input, which results in a more or less constant ice flux over the years. The positive-feedback mechanism between melt rate and ice velocity appears to be a seasonal process that may have only a limited effect on the response of the ice sheet to climate warming over the next decades.     

Ross sea region in the middle miocene: a glimpse into the past

Fossil diatoms and pollen from sea-floor sediments beneath the Ross Ice Shelf indicate that a permanent ice cover was not present in the Ross Sea and that vegetation including angiosperms, gymnosperms, and ferns existed on at least some parts of the largely glaciated Antarctic mainland in the late middle Miocene.     

Climate records covering the last deglaciation

The oxygen-18/oxygen-16 ratio of molecular oxygen trapped in ice cores provides a time-stratigraphic marker for transferring the absolute chronology for the Greenland Ice Sheet Project (GISP) II ice core to the Vostok and Byrd ice cores in Antarctica. Comparison of the climate records from these cores suggests that, near the beginning of the last deglaciation, warming in Antarctica began approximately 3000 years before the onset of the warm B?lling period in Greenland. Atmospheric carbon dioxide and methane concentrations began to rise 2000 to 3000 years before the warming began in Greenland and must have contributed to deglaciation and warming of temperate and boreal regions in the Northern Hemisphere.     

Fish, crustaceans, and the sea floor under the ross ice shelf

Baited traps and a camera lowered through the Ross Ice Shelf, Antarctica, at a point 475 kilometers from the open Ross Sea and to 597 meters below sea level revealed the presence of fish, many amphipods, and one isopod. Biological or current markings were not evident on a soft bottom littered with subangular lumps. A fish was caught through a crevasse 80 kilometers from the shelf edge.     

Changes in the west antarctic ice sheet since 1963 from declassified satellite photography

Comparison of declassified satellite photography taken in 1963 with more recent satellite imagery reveals that large changes have occurred in the region where an active ice stream enters the Ross Ice Shelf. Ice stream B has widened by 4 kilometers, at a rate much faster than suggested by models, and has decreased in speed by 50 percent. The ice ridge between ice streams B and C has eroded 14 kilometers. These changes, along with changes in the crevassing around Crary Ice Rise, imply that this region's velocity field shifted during this century.     

Inland ice sheet thinning due to holocene warmth

The climatic warming of 10,000 years ago is now affecting the central portions of ice sheets, causing ice-flow acceleration. This process explains the present-day thinning of the ice sheet in West Antarctica. Former ice sheets must have also responded to climatic warming with a delay of thousands of years. This lag in response is important in the climatic interpretation of glacial deposits and of changes in ice volume obtained from deep-sea cores.     

Ice scour disturbance in Antarctic waters

The West Antarctic Peninsula is one of the fastest warming regions on Earth, and, as a consequence, most maritime glaciers and ice shelves in the region have significantly retreated over the past few decades. We collected a multiyear data set on ice scouring frequency from Antarctica by using unique experimental markers and scuba diving surveys. We show that the annual intensity of ice scouring is negatively correlated with the duration of the winter fast ice season. Because fast ice extent and duration is currently in decline in the region after recent rapid warming, it is likely that marine benthic communities are set for even more scouring in the near future.     

Arctic air pollution: origins and impacts

Notable warming trends have been observed in the Arctic. Although increased human-induced emissions of long-lived greenhouse gases are certainly the main driving factor, air pollutants, such as aerosols and ozone, are also important. Air pollutants are transported to the Arctic, primarily from Eurasia, leading to high concentrations in winter and spring (Arctic haze). Local ship emissions and summertime boreal forest fires may also be important pollution sources. Aerosols and ozone could be perturbing the radiative budget of the Arctic through processes specific to the region: Absorption of solar radiation by aerosols is enhanced by highly reflective snow and ice surfaces; deposition of light-absorbing aerosols on snow or ice can decrease surface albedo; and tropospheric ozone forcing may also be contributing to warming in this region. Future increases in pollutant emissions locally or in mid-latitudes could further accelerate global warming in the Arctic.     

南极普里兹湾关键物理海洋学问题研究进展及未来趋势

南极普里兹湾及其邻近海域关键物理海洋学问题包括水团特性、环流特征和冰架 海洋 海冰相互作用过程等。该海域水团可以分为南极表层水、绕极深层水、南极底层水、南极陆架水和南极冰架水等,受外部条件影响,这些水团时空变化显著。普里兹湾区域的环流以普里兹湾流涡,西向的沿岸流和东向的绕极流,以及两者之间的南极辐散带的环流为主要特征,地形是环流特征的关键影响因素。埃默里冰架 海洋的相互作用过程显著影响普里兹湾海域的水团特性和环流状况。冰泵机制,是埃默里冰架外海水进入冰穴,并引起冰架底部消融和冻结的重要原因。冰架 海洋 海冰相互作用形成的低温高盐水,是普里兹湾形成南极底层水的潜在因素之一。加强现场观测,并建立高分辨率的冰架 海洋 海冰耦合模型系统是研究普里兹湾海域物理海洋学关键过程和变化机制的重要手段,是南极研究的发展趋势。     

Submarine pingos in the beaufort sea

Numerous underwater mounds found on the continental shelf of the Beaufort Sea are thought to be pingos (hills that have a central core of ice) which have formed in the marine environment subsequent to oceanic transgression.     

Pleistocene collapse of the west antarctic ice sheet

Some glacial sediment samples recovered from beneath the West Antarctic ice sheet at ice stream B contain Quaternary diatoms and up to 10(8) atoms of beryllium-10 per gram. Other samples contain no Quaternary diatoms and only background levels of beryllium-10 (less than 10(6) atoms per gram). The occurrence of young diatoms and high concentrations of beryllium-10 beneath grounded ice indicates that the Ross Embayment was an open marine environment after a late Pleistocene collapse of the marine ice sheet.     

Larsen ice shelf has progressively thinned

The retreat and collapse of Antarctic Peninsula ice shelves in tandem with a regional atmospheric warming has fueled speculation as to how these events may be related. Satellite radar altimeter measurements show that between 1992 and 2001 the Larsen Ice Shelf lowered by up to 0.27 +/- 0.11 meters per year. The lowering is explained by increased summer melt-water and the loss of basal ice through melting. Enhanced ocean-driven melting may provide a simple link between regional climate warming and the successive disintegration of sections of the Larsen Ice Shelf.     

The rise of global mean sea level as an indication of climate change

Rising mean sea level, it is proposed, is a significant indicator of global climate change. The principal factors that can have contributed to the observed increases of global mean sea level in recent decades are thermal expansion of the oceans and the discharge of polar ice sheets. Calculations indicate that thermal expansion cannot be the sole factor responsible for the observed rise in sea level over the last 40 years; significant discharges of polar ice must also be occurring. Global warming, due in some degree presumably to increasing atmospheric carbon dioxide, has been opposed by the extraction of heat necessary to melt the discharged ice. During the past 40 years more than 50,000 cubic kilometers of ice has been discharged and has melted, reducing the surface warming that might otherwise have occurred by as much as a factor of 2. The transfer of mass from the polar regions to a thin spherical shell covering all the oceans should have increased the earth's moment of inertia and correspondingly reduced the speed of rotation by about 1.5 parts in 10(8). This accounts for about three quarters of the observed fractional reduction in the earth's angular velocity since 1940. Monitoring of global mean sea level, ocean surface temperatures, and the earth's speed of rotation should be complemented by monitoring of the polar ice sheets, as is now possible by satellite altimetry. All parts of the puzzle need to be examined in order that a consistent picture emerge.     

Phytoplankton bloom produced by a receding ice edge in the ross sea: spatial coherence with the density field

Measurements of chlorophyll, particulate carbon, and biogenic silica concentrations near a receding ice edge off the coast of Victoria Land, Antarctica, indicated the presence of a dense phytoplankton bloom. The bloom extended 250 kilometers from the ice edge and was restricted to waters where the melting of ice had resulted in reduced salinity. The region involved was one of enhanced vertical stability, which may have favored phytoplankton growth, accumulation, or both. Epontic algae released from melting ice may have served as an inoculum for the bloom. Ratios of organic carbon to chlorophyll and biogenic silica to carbon were unusually high, resulting in high biogenic silica concentrations despite only moderately high chlorophyll levels.