Not all of Antarctica is ice. The McMurdo Dry Valleys form the most extensive
ice-free region on the continent, covering 4,800 square kilometers an
area somewhat larger than Delaware. Located along the Transantarctic Mountains
in southern Victoria Land, the valleys comprise a polar desert and, despite
their harshness, also host life. Their unique ecosystems make the Dry Valleys
an ideal laboratory for studying present and past climate changes.
The mean annual temperature in the McMurdo Dry Valleys is negative 20 degrees Celsius. Annual precipitation is less than 10 centimeters per year. Ice-covered lakes are fed by streams that only flow a few weeks each year during the austral summer. Cold, dry and without sunlight for months on end, the environment is truly extreme for life. As a result, the ecosystems in the valleys are unusual. No vascular plants or vertebrates dwell here. Instead, single-celled eukaryotes and prokaryotes dominate the valley, along with bryophytes and nematodes.
Camping way out: At Lake Hoare camp in Taylor Valley, tents are still the norm, as they were when researchers worked here in the 1980s. But today, these campers can report to nearby laboratories to use the latest scientific equipment or to connect to the States with e-mail.
The valleys beauty and the important climate records locked within their landscape have drawn earth scientists to study it since the International Geophysical Year (1957 to 1958). Publications in the early 1960s documented the dramatic differences in chemistry between the lakes. While studies of the dry valley region began decades ago, research was sporadic and discipline-specific for the most part. Finally, in the late 1980s and early 1990s, long-term monitoring of ecosystems came into vogue. So too did the desire for a more integrated, synthetic approach to investigating the various parts of an ecosystem and the impact of climate on an ecosystem as a whole. This change, of course, called for assembling a team of scientists from different disciplines.
In 1980, the National Science Foundation established LTER, Long-term Ecological Research, to facilitate the collection of data over time within a number of different ecological settings. A major stimulus to establishing LTER sites was the need for long-term environmental records to evaluate ecological trends and to understand the role of both natural and human disturbance on ecosystems. Today, NSF funds 24 LTER sites, two of them in Antarctica. One of these Antarctic sites is in the McMurdo Dry Valleys.
NSF established a LTER research station in the McMurdo Dry Valleys in 1993 so that scientists could begin to understand what fuels and potentially harms these unique ecosystems. The ecological research site is located between 77 degrees and 78 degrees south latitude, with the primary study area in Taylor Valley.
Here, life survives in perennially ice-covered lakes, ephemeral streams, soils and glaciers. The McMurdo site is by far the coldest and the driest of the LTER sites and represents an end-member environment that contains an ecosystem dominated by microbes. We know that the role of liquid water is critical to the existence of life within these valleys. Mapping the production, transport and accumulation of liquid water is the key to understanding how this ecosystem works. As with other desert ecosystems, the relationship of the abundance of liquid water to life here is paramount.
The role of present and past climate at McMurdo has been important in influencing overall ecosystem development and function in the Dry Valleys. Past climatic changes have left a legacy of organic matter and nutrient distribution that fuels the current ecosystem. Recent work has demonstrated that what would be considered subtle climate changes in temperate regions have profound effects on the hydrological cycles within the Dry Valleys. For example, work led by Peter Doran of the University of Illinois, Chicago, demonstrated that a decadal temperature decrease of 0.7 degrees Celsius between 1986 and 2000 greatly inhibited stream flow into the lakes, in turn impacting species diversity, total biomass and primary production in the lakes.
Research in extremes
In the early 1980s, my colleague Paul Mayewski, now at the University of Maine,
asked me to come with him to the Dry Valleys to help him resurvey some rock
glaciers. When I saw the valleys, I understood immediately that these areas
were special. I was taken by both the beauty of the valleys and their starkness,
and I marveled that lakes could exist in such environments.
Although I was only in the valleys for a few days working with Paul and his students, long after that trip I would think often of this region and compare it to more temperate desert regions I would begin to investigate later in the 1980s. Never would I have thought at that time that more than 10 years later I, an earth scientist, would be working with a multidisciplinary group of scientists to understand better how this polar desert ecosystem functions within its extreme environment.
Since my 1980s visit, the basics of working in this region have not changed, although the scale of scientific support has. Also different are the manmade elements: technological advances at the NSF research base at McMurdo Station, and the details of our laboratory and living arrangements in Taylor Valley.
Life below: Members of the limnological team drill a hole in perennial lake ice to sample water below. The soils, streams and lakes in the valleys mainly host unicellular organisms. Streams feeding the lakes flow a few weeks each austral summer. Photo by K.A. Welch, Byrd Polar Research Center.
Laboratory facilities at McMurdo are world-class: the Crary Lab resembles a university research facility with state-of-the-art labs and equipment. At Lake Hoare camp in Taylor Valley, we still sleep in tents like we did in the early 1980s. But the scientists and students studying the McMurdo Dry Valleys not only have laboratories to process biological and geochemical samples, but also have a computer connection to McMurdo for e-mail access to the rest of the world. The researchers also have access to a telephone on which they can use credit cards to make calls back home. In the early 1980s, communicating with home meant going back to McMurdo Station and waiting for a radio patch to connect with the States. Solar panels supply most of the power at the Taylor Valley camp, and the camp is managed so that all waste is returned to McMurdo Station and eventually back to the States for proper disposal or recycling.
Although our scientific and technological capabilities have improved dramatically over the years, we still must deal with the Antarctic environment. Planning ahead is a very important aspect of Antarctic research. About six months before each field season, we prepare a detailed document outlining our logistical, equipment and analytical needs for the upcoming season. Although the scientific larders at McMurdo are well stocked, we dont have the option of driving to the local Wal-Mart for parts.
Weather is always an issue. Although in December and January the weather can be calm and balmy (a few hours per day above freezing), fierce storms can happen anytime. The katabatic winds that can blow down the valley from the East Antarctic Ice Sheet can wreak havoc by halting all travel and even blowing down structures. Sometimes we must stop working because travel is impossible or dangerous. We always schedule more time in the field than needed to do the work, knowing we will lose time to weather delays. In addition, although we are provided state-of-the-art field equipment, the cold takes its toll on the equipment from time to time particularly in the early field season, when temperatures can drop down to negative 30 degrees Celsius. We must always budget down time for equipment failure.
We are also limited by the extent of the field season, which generally runs from mid-October (the austral spring) until the end of January. John Priscu from Montana State University studies the lakes in the Dry Valleys and has done field work as early as August.
During our field season, the sun is up 24 hours a day. One of the key unanswered questions about the lake ecosystems is, How do the photosynthetic organisms adapt and survive through the austral winter? Research by our colleagues Johanna Laybourn-Parry of the University of Nottingham, and Diane McKnight of the University of Colorado, has shown that the lakes host organisms capable of both generating their own energy from the Sun or inorganic chemicals, and also of generating energy by consuming organic molecules. Thus, they can be autotrophic or heterotrophic. We believe that heterotrophic processes must dominate in the lakes during winter darkness and that trophic switching by some organisms must occur, but we have little evidence. Priscu would love to lead a winter research group to study the lakes in Taylor Valley during this time of darkness.
Integrated science for an
The connections among meteorology, hydrology and ecology may be more tightly coupled in the Dry Valleys than in many other ecosystem types. Here, earth scientists and ecologists must work closely together.
In the early 1990s, R.A. Wharton Jr., currently at the Office of Polar Programs at NSF, pulled together the scientists who are now the principal investigators at the McMurdo Dry Valleys LTER station. Most importantly, Wharton brought biological and physical scientists together. Although most of us had worked with scientists of other disciplines before and most of us had conducted research in Antarctica, the process of becoming a scientific team did not occur overnight. In fact, this process is still taking place.
What did happen quickly was the collective desire to work together a far from trivial event. We all were successful individual investigators, but it was clear that in order to be a successful team, each one of us would have to relinquish a bit of ego and authority from time to time and perhaps even learn new approaches to tackling problems. In addition, we have learned to speak each others scientific language. With time our team has become scientifically tighter and personally closer.
Our team consists of eight principal investigators with disciplines ranging from glaciology to invertebrate ecology and a number of collaborators, post-docs, research scientists and both graduate and undergraduate students. Over roughly a four-month period in the austral summer, we have 28 people in the field. One person can stay the entire four months or just one month. The principal investigators come from eight different universities, so we meet twice a year to plan for the following years field season and work. During one of these meetings, students, post-docs and research scientists meet with the principal investigators to present and discuss results from the previous season. The principal investigators keep in touch with each other during the rest of the year via scheduled conference calls and e-mail.
When Wharton stepped down as the lead principal investigator toward the end of our first funding period, the group elected me as the new leader. So it came to pass that an earth scientist became the lead investigator of a project focused on ecology.
Over the past 10 years of working together, we have all come to realize that only through this integration of biological and physical sciences can we truly unravel the workings of these unusual ecosystems. It has been extremely rewarding working as a member of this group. I have learned a great deal in interacting with my biological science colleagues as they have forced me to place my own science into a more ecological context.
In turn, I believe that I have helped influence their thinking as well. The synthesis and integration of biological and physical sciences (and now social science as well) is the key to the LTER concept, and I believe our site has done an excellent job of achieving this synthesis. It has happened because we have all desired to be intellectually involved with each others work. With the rapid development of biogeosciences as a subdiscipline of the earth sciences, our group is certainly not unique. However, we have been doing biogeosciences for 10 years now. We have worked together bringing our own training and perspective to the problems of climate change in the Antarctic and their impact on ecological change.