McMurdo Dry Valleys


The McMurdo Dry Valleys are a series of largely snow-free desert valleys on the continental coastline of Victoria Land, Antarctica, east of the East Antarctic Ice Sheet and west of McMurdo Sound and the Ross Sea. The Dry Valleys are notable for being the coldest and driest desert in the world, as well as being the largest ice-free region in Antarctica; as a result, the Valleys have become a notable hotbed for scientific research in the Antarctic region. The Dry Valleys' unique climate is due to their location nestled within the Transantarctic Mountains along with high-pressure katabatic winds that scour away snowfall and humidity across the region. Surrounding mountains prevent the flow of ice from nearby glaciers. The region's geology is primarily granites and gneisses, and glacial tills dot the bedrock landscape, with loose gravel covering the ground. The Valleys are one of the driest places on Earth, though there are several anecdotal accounts of rainfall within the Dry Valleys.
The region includes many features including Lake Vida, a saline lake, and the Onyx River, a meltwater stream and Antarctica's longest river. Although no living organisms have been found in the permafrost here, endolithic photosynthetic bacteria have been found living in the relatively moist interior of rocks. Anaerobic bacteria, with a metabolism based on iron and sulfur, have also been found under the Taylor Glacier.
The valleys are located within the McMurdo Valleys Antarctic Specially Managed Area.

Climate

The Dry Valleys are one of the most extreme habitats on Earth, and are classified as a cold desert. At approximately, the valleys constitute around 0.03% of the continent and form the largest ice-free region in Antarctica.
The region's low precipitation is the result of the snow shadow that is created from the Transantarctic Mountains the valleys are situated in; the highest peaks in the region are some. As a result, much of the valley floors remain exposed and covered with loose gravel, in which ice wedge polygonal patterned ground may be observed.
The unique conditions in the Dry Valleys are caused, in part, by katabatic winds; these occur when cold, dense air is pulled downhill by the force of gravity. The dry wind evaporates the snow rapidly and little melts into the soil. During the summer, this process can take only hours.
Another important factor is a lack of precipitation. Precipitation averages around per year over a century of records, almost exclusively in the form of snow. This contributes to the low humidity of the area.
Despite a notable lack of precipitation or surface-level ice, the Dry Valley region is home to over 6000 lakes and ponds.
For several weeks in the summer, the temperature increases enough to allow for glacial melt, which causes small freshwater streams to form. These streams feed the lakes at the base of the valleys, which do not have outflow to the sea, causing them to become highly saline.
The maximum and minimum air temperatures recorded in the McMurdo Dry Valleys were at Taylor Glacier and at Lake Vida, respectively. The mean annual air temperature on the valleys floors ranged between at Lake Bonney to at Lake Vida. Within Taylor Valley, which has eight stations, the valley bottom mean annual temperatures ranged from to, in contrast to the four glaciers stations that ranged from to.
High elevation sites ranged from to. The order of mean annual temperatures among the valleys, using valley bottom stations, warmest to coldest is Miers Valley, Taylor Valley, Wright Valley and Victoria Valley.
Locations
Taylor ValleyTaylor ValleyVictoria ValleyWright ValleyHigh-altitude sites
Lake BonneyTaylor GlacierLake VidaLake VandaMt. Fleming
Parameters
Elevation meters603343901251870
Mean daily maximum °C-14.7-15.1-23.4-17.3-23.1
Daily mean °C-17.3-17.2-26.8-19.5-24.1
Mean daily minimum °C-19.2-18.7-29.6-22.0-25.2
Record high °C10.612.010.010.7-4.8
Record low °C-48.3-44.9-65.7-53.7-46.3

Geology

The McMurdo Oasis is bounded by the coastline of south Victoria Land and the Polar Plateau. The Taylor and Wright Valleys are major ice-free valleys within the Transantarctic Mountains. These "dry valleys" include hummocky moraines, with frozen lakes, saline ponds, sand dunes, and meltwater streams. Basement rocks include the Late Precambrian or Early Palaeozoic Skelton Group metamorphic rocks, primarily the Asgard Formation, which is a medium-high-grade marble and calc schist. The Palaeozoic Granite Harbour intrusives include granitoid plutons and dykes, which intruded into the metasedimentary Skelton Group in the Late Cambrian–Early Ordovician during the Ross orogeny. The basement complex is overlain by the Jurassic Beacon Supergroup, which is itself intruded by Ferrar Dolerite sheets and sills. The McMurdo Volcanic Group intrudes, or is interbedded with, the Taylor and Wright Valleys' moraines as basaltic cinder cones and lava flows. These basalts have ages between 2.1 and 4.4 Ma. The Dry Valley Drilling Project determined the Pleistocene layer within the Taylor Valley was between 137 and 275 m thick, and composed of interbedded sandstones, pebble conglomerates, and laminated silty mudstones. This Pleistocene layer disconformably overlies Pliocene and Miocene diamictites.

Research

Since the Valleys' discovery in the early 1900s and the establishment of McMurdo Station and Scott Base as research stations on nearby Ross Island in the 1950s, the Dry Valleys region has been extensively studied by scientists. The valleys' hyper-arid, cold-desert climate was soon identified as a high-fidelity terrestrial analogue for the environment of Mars, and geologists and astrophysicists have subsequently used the Valleys as a testing ground for analog-based studies since NASA's Viking Program in the 1970s.
In 1985, the first continuously operating meteorological station was installed at Lake Hoare, and in 1992, Taylor Valley, the southernmost of the three major Dry Valleys, was selected as a National Science Foundation Long Term Ecological Research site, enabling for long-term scientific investigation of ecological processes over decadal timescales., there are a total of 26 real-time meteorological stations, stream gauges, and observing platforms and a total of 1028 unique scientific publications affiliated or supported by the LTER program.
Irish and American researchers conducted a field expedition in 2013 to University Valley in order to examine the microbial population and to test a drill designed for sampling on Mars in the permafrost of the driest parts of the valleys, the areas most analogous to the Martian surface. They found no living organisms in the permafrost, making University Valley the first location on the planet visited by humans with no detected active microbial life.
Similarly, much research has been done on analyzing the various ice-covered lakes and streams in the valleys. The lakes are unique physically due to a climate-induced balance between the maintenance of a thick, permanent ice cover due to low temperatures, the loss of ice to sublimation, and the replacement of water into the lakes themselves from seasonal glacial meltwater inflow.
Research has discovered the presence of microbial mats along glacial-melt streams, lakes, wetlands, and ice in the region. Dry Valley microbial mats are unique due to the constant scouring from katabatic winds.
Endolithic bacteria have been found living in the Dry Valleys, sheltered from the dry air in the relatively moist interior of rocks. Summer meltwater from the glaciers provides the primary source of soil nutrients.
Anaerobic bacteria whose metabolism is based on iron and sulfur live in sub-freezing temperatures under the Taylor Glacier.
It was previously thought that algae were staining the red ice emerging at Blood Falls, but it is now known that the staining is caused by high levels of iron oxide.
In 2014, drones were used in the McMurdo Dry Valleys by a team of scientists from Auckland University of Technology (AUT) to create baseline maps of the vegetation. In 2015, the New Zealand Antarctic Research Institute granted funding to AUT to develop methods for operating unmanned aerial vehicles. Over successive summer seasons in Antarctica, the AUT team created three dimensional maps with sub-centimeter resolution, which are now used as baselines.
Part of the Valleys was designated an environmentally protected area in 2004.

Major geographic features

Valleys

From north to south, the three main valleys are
West of Victoria Valley are, from north to south,
Stretching south from Balham Valley are, from west to east:
West of Taylor Valley is
Further south, between Royal Society Range in the west and the west coast of McMurdo Sound at the lobe of Koettlitz Glacier are, from north to south:

Glaciers

Wright Valley

Taylor Valley

Lakes

Some of the lakes of the Dry Valleys rank among the world's most saline lakes, with a higher salinity than Lake Assal or the Dead Sea. The most saline of all is small Don Juan Pond.

Former lakes

Rivers

Other