Distribution and abundance of soil fungi in Antarctica at sites on the Peninsula, Ross Sea Region and McMurdo Dry Valleys

The McMurdo Dry Valleys are a polar desert in coastal Antarctica, where glaciers, permafrost, ice-covered lakes, and ephemeral summer streams coexist. Liquid water is found at the surface only in lakes and in the temporary streams that feed them. Past geophysical exploration has yielded ambiguous results regarding the presence of subsurface water. In 2011, we used a helicopter-borne, time-domain electromagnetic (TDEM) sensor to map resistivity in the subsurface across the Dry Valleys. The airborne electromagnetic (AEM) method excels at finding subsurface liquid water in polar deserts, where water remains liquid under cold conditions if it is sufficiently saline, and therefore electrically conductive. Over the course of 26 h of helicopter time, we covered large portions of the Dry Valleys and vastly increased our geophysical understanding of the subsurface, particularly with respect to water. Our data show extensive subsurface low-resistivity layers approximately 150–250 m below the surface and beneath higher resistivity layers. We interpret the low-resistivity layers as geologic materials containing freeze-concentrated or “cryoconcentrated” hyper saline brines lying beneath glaciers and frozen permafrost. These brines appeared to be contiguous with surface lakes, subglacial regions, and the Ross Sea, which could indicate a regional-hydrogeologic system, wherein solutes might be transported between surface reservoirs by ionic diffusion and subsurface flow. The presence of such brines underneath glaciers might have implications for glacier movement. Systems such as this, where brines exist beneath glacial ice and frozen permafrost, may exist elsewhere in coastal Antarctica; AEM resistivity is an ideal tool to find and survey them. Our application of TDEM demonstrates that in polar subsurface environments containing conductive brines, such a diffusive electromagnetic method is superior to radar surveying in terms of depth of penetration and ability to differentiate hydrogeologic conditions.

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Hydrologic response to extreme warm and cold summers in the McMurdo Dry Valleys, East Antarctica

Antarctic Science ◽

10.1017/s0954102008001272 ◽

2008 ◽

Vol 20 (5) ◽

pp. 499-509 ◽

Cited By ~ 102

Author(s):

Peter T. Doran ◽

Christopher P. McKay ◽

Andrew G. Fountain ◽

Thomas Nylen ◽

Diane M. McKnight ◽

...

Keyword(s):

Lake Level ◽

Ross Sea ◽

Ice Core ◽

Fold Increase ◽

Mcmurdo Dry Valleys ◽

Dry Valleys ◽

Hydrological Response ◽

Sea Level Pressure ◽

Significant Difference ◽

Warm Summer

AbstractThe meteorological characteristics and hydrological response of an extreme warm, and cold summer in the McMurdo Dry Valleys are compared. The driver behind the warmer summer conditions was the occurrence of down-valley winds, which were not present during the colder summer. Occurrence of the summer down-valley winds coincided with lower than typical mean sea level pressure in the Ross Sea region. There was no significant difference in the amount of solar radiation received during the two summers. Compared to the cold summer, glaciological and hydrological response to the warm summer in Taylor Valley included significant glacier mass loss, and 3- to nearly 6000-fold increase in annual streamflow. Lake levels decreased slightly during the cold summer, and increased between 0.54 and 1.01 m during the warm summer, effectively erasing the prior 14 years of lake level lowering in a period of three months. Lake level rise during the warm summer was shown to be strongly associated with and increase in degree days above freezing at higher elevations. We suggest that strong summer down-valley winds may have been responsible for the generation of large glacial lakes during the Last Glacial Maximum when ice core records recorded annual temperatures significantly colder than present.

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Foehn Winds in the McMurdo Dry Valleys, Antarctica: The Origin of Extreme Warming Events*

Journal of Climate ◽

10.1175/2010jcli3382.1 ◽

2010 ◽

Vol 23 (13) ◽

pp. 3577-3598 ◽

Cited By ~ 56

Author(s):

Johanna C. Speirs ◽

Daniel F. Steinhoff ◽

Hamish A. McGowan ◽

David H. Bromwich ◽

Andrew J. Monaghan

Keyword(s):

Ross Sea ◽

Mcmurdo Dry Valleys ◽

Dry Valleys ◽

Pressure Gradients ◽

Synoptic Scale ◽

Mountain Wave ◽

Mountain Ranges ◽

Surface Weather ◽

Weather Stations ◽

The Antarctic

Abstract Foehn winds resulting from topographic modification of airflow in the lee of mountain barriers are frequently experienced in the McMurdo Dry Valleys (MDVs) of Antarctica. Strong foehn winds in the MDVs cause dramatic warming at onset and have significant effects on landscape forming processes; however, no detailed scientific investigation of foehn in the MDVs has been conducted. As a result, they are often misinterpreted as adiabatically warmed katabatic winds draining from the polar plateau. Herein observations from surface weather stations and numerical model output from the Antarctic Mesoscale Prediction System (AMPS) during foehn events in the MDVs are presented. Results show that foehn winds in the MDVs are caused by topographic modification of south-southwesterly airflow, which is channeled into the valleys from higher levels. Modeling of a winter foehn event identifies mountain wave activity similar to that associated with midlatitude foehn winds. These events are found to be caused by strong pressure gradients over the mountain ranges of the MDVs related to synoptic-scale cyclones positioned off the coast of Marie Byrd Land. Analysis of meteorological records for 2006 and 2007 finds an increase of 10% in the frequency of foehn events in 2007 compared to 2006, which corresponds to stronger pressure gradients in the Ross Sea region. It is postulated that the intra- and interannual frequency and intensity of foehn events in the MDVs may therefore vary in response to the position and frequency of cyclones in the Ross Sea region.

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Monsoonal circulation of the McMurdo Dry Valleys, Ross Sea region, Antarctica: signal from the snow chemistry

Annals of Glaciology ◽

10.3189/172756404781814087 ◽

2004 ◽

Vol 39 ◽

pp. 139-145 ◽

Cited By ~ 24

Author(s):

Nancy A. N. Bertler ◽

Paul A. Mayewski ◽

Peter J. Barrett ◽

Sharon B. Sneed ◽

Michael J. Handley ◽

...

Keyword(s):

Radiative Forcing ◽

Climate Model ◽

Ross Sea ◽

Function Analysis ◽

Mcmurdo Dry Valleys ◽

Ion Concentration ◽

Dry Valleys ◽

Air Mass ◽

Snow Chemistry ◽

Extreme Seasonality

AbstractMcMurdo Dry Valleys (MDV; Ross Sea region, Antarctica) precipitation exhibits extreme seasonality in ion concentration, 3–5 orders of magnitude between summer and winter precipitation. To identify aerosol sources and investigate causes for the observed amplitude in concentration variability, four snow pits were sampled along a coast–Polar Plateau transect across the MDV. The elevation of the sites ranges from 50 to 2400 m and the distance from the coast from 8 to 93 km. Average chemistry gradients along the transect indicate that most species have either a predominant marine or terrestrial source in the MDV. Empirical orthogonal function analysis on the snow-chemistry time series shows that at least 57% of aerosol deposition occurs concurrently. A conceptual climate model, based on meteorological observations, is used to explain the strong seasonality in the MDV. Our results suggest that radiative forcing of the ice-free valleys creates a surface low-pressure cell during summer which promotes air-mass flow from the Ross Sea. The associated precipitating air mass is relatively warm, humid and contains a high concentration of aerosols. During winter, the MDV are dominated by air masses draining off the East Antarctic ice sheet, that are characterized by cold, dry and low concentrations of aerosols. The strong differences between these two air-mass sources create in the MDV a polar version of the monsoonal flow, with humid, warm summers and dry, cold winters.

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