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Picture 1: Map of the Dry Valleys. The Lake Hoare and F6
campsites in Taylor Valley are shown with stars.
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| Picture 2: View of Taylor Valley. |
The McMurdo Dry Valleys are a series of ice-free elongate
valleys located approximately 50 miles across McMurdo Sound from our current
location (Pictures 1&2). The Valleys increase in elevation as you move away from
McMurdo Sound, and the upper ends of the valleys are occupied by glaciers.
These mountains were initially formed during the late Mesozoic Era (~135-180
mya), when Antarctica broke away from other continents and began its southward
trajectory to its current location. These mountains are particularly important because
they have largely diverted ice flows from the Antarctic continental ice sheet
around this area, thus keeping the valleys ice-free. However, during previous
glacial periods, glaciers extended well into the valleys and carved them out
into their present form.
The Dry Valleys are considered a polar desert, and are one
of the driest places on Earth. One of the primary reasons is because the area receives
so little precipitation, the water equivalent of about 5cm a year (less than
Las Vegas!). Another reason is because cold winds that originate on the
Antarctic ice sheet swoop into the valleys and prevent the chance of
precipitation. These unique environmental conditions have existed for hundreds
of thousands if not millions of years.
So if it’s so cold and dry how are we able to study
streamflow in the Dry Valleys? The answer is a few weeks out of the year a
combination of relatively higher temperatures and an increase in sunlight
during the summer months initiates melting in the glaciers that are located
along the edges of these valleys. This glacial melt water becomes the primary
source of streamflow in the Dry Valleys. Another relatively minor contribution
to streamwater can come from the melting of permafrost, or frozen water, stored
just beneath the surface in the surrounding soils. Therefore, each year’s
stream flow is ultimately dependent on the relative warmth of that particular
summer.
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Picture 3: View of Lake Hoare, one of the many closed basin
lakes located in the Dry Valleys
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What has drawn so many scientists to study the Dry Valleys
is that they are the closest environment we have on Earth to what we might
expect on Mars. It is generally accepted that Mars had significant quantities
of water in the distant past. However, for reasons we don’t completely understand,
much of this atmosphere is gone and any water is limited to either ice caps at
the poles or in the soil as permafrost. This hopefully sounds similar, since it
parallels what I mentioned about the primary sources of water in the Dry Valleys.
Furthermore, some scientists think the Dry Valleys represent the late stages of
water cycle evolution on Mars. With seasonal melting from glaciers or ice caps
feeding closed basin lakes (Picture 3).
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| Picture 4: Different life forms found in the Dry Valleys include but are not limited to: (a) lichen, (b) nemotodes, and (c) cyannobacteria mats (Sources: [a&b] NZ Antarctic Biocomplexity Survey, and [c] USFWS Marine Fisheries Research Office). |
Finally, many scientists come to the Dry Valleys to study
its life forms. After looking at the above pictures you might ask where is the
life? However, it turns out the Dry Valleys are teeming with life, just not in
forms that we can readily see with the naked eye (Picture 4). Algae are found in the
glaciers and lakes, and fractures in rocks (along with lichens). In some locations, cyanobacteria mats are
located along streams or in the lakes. The soils have also been found to
contain a large diversity of microbes along with nematodes or roundworms. All
of the life forms have managed to adapt to an extremely harsh environment. For
a complete description of all the different life forms found to date in the
valleys, you can click here: http://nztabs.ictar.aq/dv-biology.php.
In the next post I’ll elaborate more on my own experiment
and how it will hopefully contribute to our knowledge of the Dry Valleys.
