Distribution and origin of ground ice in University Valley, McMurdo Dry Valleys, Antarctica

Abstract

Ground ice is one of the most important and dynamic geologic components of permafrost; however, few studies have investigated the distribution and origin of ground ice in the McMurdo Dry Valleys of Antarctica. In this study, ice-bearing permafrost cores were collected from 18 sites in University Valley, a small hanging glacial valley in the Quartermain Mountains. Ground ice was found to be ubiquitous in the upper 2 m of permafrost soils, with excess ice contents reaching 93%, but ground ice conditions were not homogeneous. Ground ice content was variable within polygons and along the valley floor, decreasing in the centres of polygons and increasing in the shoulders of polygons towards the mouth of the valley. Ground ice also had different origins: vapour deposition, freezing of partially evaporated snow meltwater and buried glacier ice. The variability in the distribution and origin of ground ice can be attributed to ground surface temperature and moisture conditions, which separate the valley into distinct zones. Ground ice of vapour-deposition origin was predominantly situated in perennially cryotic zones, whereas ground ice formed by the freezing of evaporated snow meltwater was predominantly found in seasonally non-cryotic zones.

Cryostratigraphy and the Sublimation Unconformity in Permafrost from an Ultraxerous Environment, University Valley, McMurdo Dry Valleys of Antarctica

“…In the low frost‐susceptible sediments of University Valley, four types of cryostructures were observed, including: structureless, porous visible, suspended and crustal, irrespective of their location in the valley (PCZ, NCZ or IMZ) and the associated origin of ground ice: vapour‐deposited ground ice in the PCZ and freezing of partially evaporated snow meltwater in the NCZ (Lacelle et al, ; Lapalme et al, ). Therefore, the type of cryostructure observed in the cores could not be used to infer the mode of emplacement of ground ice.…”

“…These cores were selected because of their location in the valley with respect to the ground‐surface temperature zones and ground‐ice origins (Table ). P8 and P6 are situated in the PCZ and the IMZ, respectively, where the ground ice in the cores was attributed to vapour deposition, whereas P1 and P7 are situated in the NCZ, where the ground ice formed by the freezing of partially evaporated snowmelt water (Lapalme et al, ).…”

“…Fisher et al () concluded that the measured ice‐table depths are probably in equilibrium with present‐day ground‐surface temperature and humidity conditions. Ground ice is abundant below the ice table, with excess ice contents, excluding the two buried glacier‐ice bodies, reaching 93 per cent (Lapalme et al, ). Based on δD–δ 18 O measurements, ground ice has been attributed to three different origins: (1) vapour deposition in the sediments from the PCZ; (2) freezing of partially evaporated snow meltwater in the sediments from the NCZ; and (3) buried glacier ice at two localities (Lacelle et al, , ; Pollard et al, ; Lapalme et al, ).…”

“…In University Valley, situated in the upper McMurdo Dry Valleys (MDV) of Antarctica, icy permafrost was found below a shallow ice table (McKay, ; Marinova et al, ). Based on its δD–δ 18 O composition, the ground ice in the sandy sediments was emplaced by three different mechanisms: vapour deposition, freezing of partially evaporated snow meltwater and burial of glacier ice (Lacelle et al, , ; Pollard et al, ; Lapalme et al, ). The differing ground‐ice emplacement processes in University Valley allow us to assess the application of cryostratigraphy in an ultraxerous region and its potential to help infer the origin of ground ice and the past permafrost conditions (i.e.…”

Physicochemical and Biological Controls on Carbon and Nitrogen in Permafrost from an Ultraxerous Environment, McMurdo Dry Valleys of Antarctica

“…The permafrost table along the floor of University Valley is at the ground surface (Lacelle et al, ), whereas the ice table ranges in depth from 0 cm near the glacier to approximately 60 cm at the mouth of the valley (Fisher et al, ; Marinova et al, ; McKay, ). Ground ice is abundant below the ice table and has been attributed to three different origins: (1) vapor deposition in soils from the PCZ; (2) freezing of partially evaporated snow meltwater in soils from the NCZ; and (3) buried glacier ice at two localities (Lacelle et al, , ; Lapalme et al, ; Pollard et al, ). Despite having distinct ground ice origins between the ground surface temperature zones, ice accumulation rates are similar along the valley, ranging from 1 to 10 mm kyr ‐1 (Lapalme, Lacelle, Pollard, Fortier, et al, ).…”