What is the deepest part of the Vostok ice core telling us?

Limnological conditions in Subglacial Lake Vostok, Antarctica

“…The basal portion of the ice core from 3,539 to 3,623 m (Fig. 1C) has a chemistry and crystallography distinctly different from the overlying glacial ice, including extremely low electrical conductivity, large ice crystals , and numerous macroscopically visible sediment inclusions (Simõ es et al 2002;Souchez et al 2002;Royston-Bishop et al 2005). The geochemical composition of this basal ice, in concert with the geophysical data, indicates that the basal portion of the core represents actual lake water that has accreted (i.e., frozen) to the underside of the ice sheet.…”

Twenty Years of Drilling the Deepest Hole in Ice

“…Between 3310 m and 3539 m, the glacial core is disturbed by bedrock deformation (Souchez et al, 2003). Information on microparticles, crystal sizes, and chemical element distributions in that part of the core shed new light on this deformation process-the ice deformation occurred when the ice was still grounded upstream from Vostok station in a region with subfreezing temperatures.…”

The Mid-Pleistocene Transition and the Vostok Oldest Ice Challenge

“…This is what Paillard [27] and Paillard and Parrenin [29] showed by using a simple conceptual model with multiple equilibria (threshold model) in the climatic I -undisturbed section of the Vostok meteoric ice containing continuous climatic record (0-3310 m); II -disturbed section of the meteoric ice (3310-3539 m), in which two distinct strata can be discerned: in the stratum between 3310 and 3460 m a largescale folding of ice is presumed, in the stratum between 3460 and 3538 m the submetric scale ice interbedding is observed; III -accreted ice refrozen from Lake Vostok's water . The deuterium profile is composed from available published data [1,31,40] (axis is not shown) Рис. 1.…”

“…Восток . Изотопный про филь (δD) построен по опубликованным данным [1,31,40] (шкала δD не показана) system to simulate, within the framework of the as tronomical theory, the onset of a prominent 100 ka cycle at the time of the MPT, by adding a longterm drift reflecting the cooling since the Miocene .…”

“…Earlier works have shown that complex ice deformation, which has occurred when the ice was still grounded upstream from Vostok Station, resulted in the folding and intermix ing of ice at a submetric scale in the stratum bedded below 3450-3460 m and at a larger scale between 3310 and 3450 m (see Fig . 1) [18,[39][40][41] . Using an appropriate correction of the ice stratigraphy for flow disturbance in the 3320-3345 m interval, it has only been possible to extend the Vostok ice record further back to 440 kyr BP, which implies full cov erage of the Marine Isotope Stage (MIS) 11 [36] .…”