Field Trips, Field Trips and More Field Trips...

Sorry to have been away from my computer for so long. I've been busy seeing more of Antarctica, specifically the ANDRILL drill site, Robert Scott's hut at Cape Evans, and the Wright Valley. In this blog I'll start with the most recent trip and work backwards because I really want to share this photograph with you.

On Wednesday (11/28) a group of us from ANDRILL went on a field excursion to one of the valleys. We flew in aboard a helicopter that dropped us on the flat area near where I'm standing. Here is a quote from the introduction section of the Wright Valley Field Excursion guide given out to us:
"The Dry Valleys have long been a feature of great interest on the Antarctic continent. Not only because of their unique absence of ice and snow but as a result of this, their accessibility to geologic features that are ice covered in a majority of the continent. Little was known of the region until 1955 when the New Zealand party of the Commonwealth Trans-Antarctic Expedition, 1955-1958, resulted in the first thorough geologic assessment of Victoria Land." (Peter Webb, whom I photographed at our Open House, was one of the students on that expedition.) "...On this trip a variety of erosional and depositional features will be observed that reflect the complex Cenozoic history of the region."

In the photograph above, the distant peaks behind where I'm standing you can see the deposited layers that are lighter in color. Those layers are part of the Beacon Supergroup composed of sedimentary rocks like siltstones, limestones and sandstones and also have fossils of fresh water fish and plants from the Mesozioc Triassic time. The valley that is directly behind me clearly shows erosion from giant glaciers during the Cenozoic era. The other thing you should note is the glacier way off in the distance. That is the Wright Upper Glacier. Beyond that is the East Antarctic ice sheet that covers the largest portion of the continent.

One of the other cool things about this are is that the ground responds to the temperature fluctuations, freezing and thawing causing cracks that form the land into pattern ground- connected polygons. If you look closely at this photograph you will see some rocks laying flat and some sitting on edge. If you look at the lines created by the rocks sitting on their edges you will see lines that meet where the snow is. This is where three polygons of the pattern ground join together. As the helicopter took us to the bottom of the valley I took this next photograph of the valley floor where you can see some of these polygons, pattern ground.

The helicopter dropped us off at a New Zealand hut next to Vanda Lake. We left our gear and hiked around until lunch, came back to the hut and feasted. (I'm glad there was a port-o-potty next to the hut!) We picked up our gear and hiked a few more miles through what will be a very broad, shallow stream bed later in the season. For now, it was dry sand and pebbles.








We dropped our stuff off again at a US hut where some guys were working on the upkeep of a seismic array. They had a very cozy hut and had coffee waiting for us! That's one thing I really, really like about being here- everyone is a friendly neighbor. Too bad we can't all live that way off ice. After coffee and more hiking, the helicopter picked us up right on time and delivered us back to McMurdo just in time for dinner.

This photo shows the lower portion of the Wright Valley. Imagine where I was standing in the first photo as the top of the valley, this would be near the middle and the Ross Sea is still beyond.

Antarctica is a Desert

This is a question I got from Children in Room 133 at Talahi Community School:

“We are studying deserts this week. We heard that Antarctica might be considered a desert! Can you tell us about this?”

Antarctica is indeed a desert, in fact it is the largest desert (about 14.2 million square kilometers in size) on planet Earth. Specifically it is a cold desert. This may surprise many people, because people usually think of deserts as being hot, like the Sahara Desert (just over 9 million square kilometers), but that does not have to be the case. Deserts are defined as regions that have less than 254 mm (10 inches) of precipitation per year. Precipitation means water that can fall as rain, sleet, hail or snow.

Another definition of a desert is ‘an area where there is a greater rate of evaporation than precipitation (rain, hail or snow)’. Because the average temperature in Antarctica is typically below zero degrees Celsius (32 degrees Fahrenheit), combined with the fact that cold air cannot hold as much moisture as warm air, it is usually too cold for precipitation to occur.

In the interior of the Antarctic Continent the average annual precipitation (snowfall is recalculated at its “water equivalent”) is only about 50 mm (about 2 inches). The amount of precipitation does increase towards the coasts, but it is still only about 200 mm (8 in). Air over Antarctica is generally too cold to hold water vapor – so there is very little evaporation. This means that when snow does fall in Antarctica, it usually stays there – or gets blown around, and it eventually accumulates over hundreds and thousands of years into thick ice sheets, like the West Antarctic Ice Sheet and the East Antarctic Ice sheet.

I have noticed the really strong winds that typically come from the south. What I have noticed is that the winds are usually blowing snow, which makes it look as though it may be snowing, but it isn’t. The ever-present winds pick up snow that has already fallen and move it around from place to place, producing ‘white-out’ conditions, which would constitute a ‘Condition 1’ in McMurdo-speak. What I have noticed is that I can tell when the snow around McMurdo has just been blown around, because it usually has a slightly brown color; this is because it has picked up lots of tiny grains of silt or mud (‘rock dust’) from the rocks that are sticking up above the ice and snow, and carried it with the blowing snow, then dropped them with the snow when the winds died down.

In fact, I was helping take some core boxes down to the helo pad one day, and we were also taking some big yellow buckets down there. Apparently the people out at the drillsite had noticed all the windblown dust with the snow, and they wanted to collect some, because they were curious about how much there was, and what the composition of the particles was. I’ll have to ask them how they set the giant buckets up to collect the wind-blown dust, and find out whether they have managed to collected dusty particles.

By the way, I went for a very nice short walk this evening part way around Observation Hill. It was one of the calmest (wind-free!) evenings we have had since I have been here.

Snow Day from 11/08/07

Snow Day- 11/8

The weather wasn’t very good for doing science yesterday. The crew went out for a bit, but had to come back to came when snow started to fall making visibility a problem. Dr. Marv Speece entertained us in the afternoon with a lecture on geophysics. We went to bed last night with fluffy snowflakes falling through still air. Sometime around three this morning the wind started howling so that the tents were all flapping frantically. Needless to say, no data collection again today. It’s hard to tell if it’s currently snowing or are the 20+ mph winds just blowing the fluff that fell yesterday. Current temperature is around 17F, positive numbers thank goodness. Anyway, it’s hard to see much except shades of white and gray, and even more difficult to function outside for very long.

Our chief, Dr. Ross Powell, Glacial Sedimentologist from Northern Illinois University, continued our lecture series on glaciers in the science tent. Ross first visited Antarctica in the 70’s as a graduate student and has been here numerous times since then. He’s been particularly interested in the Mackay glacier over the last ten years and is very keen to get some good sediment records showing up on our seismic survey. On days that we’re working at the survey site, his primary responsibility is supervising the data collection process and pondering the great complexities of glacier behavior.

Today’s lecture focused on different types of glaciers, their behaviors and sediment records based on climatic differences, and how that all relates to future climate changes. I asked Ross to explain what we’re all doing here in Granite Harbor and gave him a two paragraph maximum.

Ross says, “On the continental shelf around Antarctica are some very deep troughs and basins that were scoured and eroded out when the ice sheet was much larger and expanded over those areas. Since the ice sheet last started to shrink and retreat, some of those troughs and basins, which can reach over 900 meters below sea level, have been special repositories for marine sediment. Ocean currents have carried and concentrated sediment in the basins so that it accumulates very rapidly, at a rate of several millimeters every decade. Because these basins have been exposed and have been receiving this sediment over the past 20,000 to 7,000 years as the ice sheet retreated and opened-up the continental shelf, thick accumulations of these geologically very young sediments has been stored in the basins, some now reaching up to 200 meters thick. These thick piles of sediments are made mainly of the remains of marine plants or algae named diatoms that form the basis of the food web in the highly productive Southern Ocean. These marine plants need sunlight and a good supply of nutrients from the water to flourish; some even like living in sea ice that forms every winter around Antarctica by sea water freezing. Nutrients are best provided by strong winds blowing across the water surface causing deep waters that carry the nutrients to rise up to the surface where the diatoms live.

What we want to do is core one of these types of sediment records that now lie at the bottom of the Mackay Sea Valley, and look for periods of time in the core when diatoms were flourishing and when they weren’t, going back over the last 7,000 years. Other types of sediment accumulate when diatoms are not abundant, because waters are either less nutritious or perhaps were covered with very thick sea ice cutting down on the sunlight reaching the upper seawater layer. These types of records can tell us a great deal about the ocean circulation changes over time, which we want to understand, and compare those changes in Antarctica with what has happened in lower latitudes such as around New Zealand and even in tropical waters closer to the equator. We need to understand how these ocean waters in different areas of the world are linked to each other, so we can better predict how they may change as global warming continues. It is especially important for Antarctica because of the possibility of all of its ice melting as Earth continues to warm.”

Thank you very much, Ross!

Field trip to the Mackay Glacier

A couple of days ago we completed our tasks for the day a little early so our chief scientist, Dr. Ross Powell, took us on a field trip out to see the Mackay Glacier up close. Our seismic survey is mapping sediment deposited by the Mackay and this was a great opportunity to understand the depositional process better. To get there from our camp we had to take a very bumpy, 45 min. Pisten Bully ride over multi-year ice. Our camp and survey line are located on single season ice, which means the ice breaks up and flows out to sea every season. That can be a little dangerous as the season goes on, but the ice is fairly smooth and easy to travel over. The multi-season ice is not smooth, at all!!!!

[Note that there was a movie that should be inserted here, but it is too large to insert - Ed.)

Once we had our brains unrattled (which isn’t really a word, but I’m exercising artistic license) we were amazed to find ourselves dwarfed by ice.The Mackay is an outlet glacier from the east Antarctic ice sheet flowing from a high mountain plateau. It ends as a tongue that sticks out onto the sea ice. The forward edge of the tongue shoves the sea ice ahead of it, creating sea ice chunks that often stand vertically reminding me of sculptural works.
In those areas melt pools form this time of year and are great places to find seals. Around the edges of the melt pools delicate ice crystals form. You do have to watch where you step in these areas to make sure you don’t fall into a crack. Some can be fairly deep,but Galen the mountaineer/field safety specialist makes sure we don’t get into trouble.

As the glacier makes its way to the sea, it flows over and through granite and dolerite formations. The sea ice gets shoved up against the cliff sides causing great undulations.
The younger, darker dolerite sits on top of the older, lighter color granite.
Jacob, a student from University of Nebraska, was very excited to examine the crystalline structure of this boulder up close.
As we walked through one of the glaciers canyons, we spotted pockets of clear ice that form when melt water within the glacier refreezes.
If you look closely you can see some sediment trapped in the clear ice. These sediments are carried out to sea and as the glacier melts, drop to the sea floor creating sediment layers that show up in the seismic survey data.
Some members of our party in the distance behind me were trying to find clear ice without sediment to bring back to camp to cool their beverages. I’m not sure why they need ice when you can just stick drinks outside for a couple of minutes! But then, how many times in your life can you say you’ve eaten ice that’s thousands of years old.