This blog is an outgrowth of my own research examining the past temperature of Earth’s surface and the relationship of temperature to the Earth’s carbon system. I became interested in the scientific aspects of this work as a geology undergraduate, staring at regular layers of rocks in the countryside of central Italy, back and forth, dark and light. These layers were related to past oscillations of the climate, warmer and cooler, related to long-term changes in the incoming solar radiation entering our planet from the sun. Such changes are small, but positive and negative feedbacks in the Earth system interact to translate the small changes into the radically layered rocks we see in outcrops. This was the start of a journey of discovery that continues to this day and is the foundation of my research at the Lamont-Doherty Earth Observatory.
How does the carbon dioxide (CO2) content of the atmosphere influence climate? This question was first seriously considered in the mid- to late-1800s, amid an accelerating, newfound interest in the natural sciences on the European continent. Specifically, the Victorians were fascinated by looking backward in time, at periodic extreme cold spells, also known as ice ages, when glaciers as tall as skyscrapers covered vast areas of land that today are free from ice.
The discourse about past climates began with this approach, through a discussion about how the driving forces in the Earth system might have caused our globe to periodically enter and exit the ice ages. Many factors, including emissions from volcanoes, the rearrangement of continents, the evolution of plants and vegetation, solar sun-spot cycles, and even asteroid impacts can and do impact the average surface temperature of the planet.
Yet time and again scientists returned to the role that greenhouse gases, and specifically carbon dioxide (CO2), play in the climate system. CO2 molecules in the atmosphere absorb heat (infrared radiation) coming from the Earth’s surface and then re-radiate some of that heat back to the surface to generate a warming effect. How is this related to the glacial ice age cycles of the past?
One way to think about this problem is to imagine the Earth system as a huge, naturally occurring experiment (though the sample size by most experimental standards is low). Sometimes the Earth has been warmer than today, even ice-free at the poles. When the ice melts, sea level rises, continents spring back after being depressed by the weight of the ice, and plants that need warmer weather expand their habitat pole-ward. The Earth has also been cooler than today, most recently at the last glacial maximum (~20 thousand years ago) when more ice was locked up in the polar ice sheets rather than in the ocean, making for lower sea level, which exposed more of what is today the ocean floor.
Today the framework of thought has turned around, so that instead of looking back through time to understand the climate of the past, we also try to learn lessons from the past to further our understanding of the climate of the future. By burning fossil fuels for heating, electricity, transportation and other purposes, humans add CO2 to the atmosphere. Yet, by comparing ways in which the Earth’s temperature, CO2 concentration, sea level and ice sheets have changed in the past, we are able to learn valuable lessons about the climate system of today and tomorrow. You can share in this adventure here.
One last word of caution: At the turn of the last century, people also began to wonder if land-use and manufacturing—human-induced variability—could play a role in climate. Because this issue has become highly politicized, I won’t get into all the back-and-forth arguments here. That forum has other locations online. However, for a modern history of this fascinating topic, check out the American Institute of Physics (which can be found at http://www.aip.org/history/climate/co2.htm); and for more on the science, check out what the EPA has to say (http://www.epa.gov/climatechange/ghgemissions/gases/co2.html). Both purport an objective analysis of both the history and basic science involved.
Migrating south in the winter is a behavior that Antarctic scientists share with many species of birds, although the scientists fly just a bit further south. For the IcePod team, it was time to join the migration so they could test their equipment in the most challenging environment the Earth has to offer. After three “equipment shake down” trips to Greenland over the last two years, 20 hours of flight time have been set aside for flights in Antarctica, part of the final hurdle in the commissioning of the pod.
The team arrived early this month at McMurdo Base on a large C-17 to –14°F weather and beautiful clear blue sky as the plane touched down on the Pegasus Blue Ice Runway. The first few days were spent in training for everything from driving trucks in the cold to being environmentally sensitive to the Antarctic microbes to a crash course on interpreting the complex way trash is handled in Antarctica — an impressive 60 percent of everything is recycled.
The gear arrived soon after the team… first the gravity meter, borrowed from New Zealand, wrapped in a warm, manly pinkish quilt. With many boxes being stacked in the aircraft, the color was selected for its high visibility to assist with quick location and unloading. The IcePod and the equipment rack had paused on their trip down in Pago Pago, arriving a few days after the rest of the gear, but it was all quickly set up and humming in a bright yellow and blue rack tent next to the Willy Airfield on the Ross Ice Shelf. While waiting to fly, a GPS was installed on top of the tent, and equipment was set up to test performance. Both the GPS and the gravity meter measured the movement of the ice shelf as it shifted up and down on the tide ~ 1 meter a day. In addition to the rhythmic up/down movement, the tent, the airfield and the ice shelf are all moving northwards at 30 cm or 1 foot a day.
Finally, IcePod was cleared to fly and complete her first Antarctic survey mission installed on a Pole Tanker mission flying on Skier 95. The flight was delayed as the C-17 practiced airdrops over the South Pole runway, but as soon as the C-17 was out of the way, icePod took off and headed south.
Low elevation data was collected on the way out to make sure the C-17 was clear. All the instruments worked in the flight across the very flat Ross Ice Shelf, then over the Transantarctic Mountains and across the spectacular East Antarctic Ice Sheet.
The low angle of the sun made the mountains, crevasses and wind scour areas stand out beautifully in the imagery. The deep radar imaged the structure of the Ross Ice Shelf even from 21,000 feet. The infra-red camera showed the variable temperature of the different types of ice in the Beardmore Glacier and the high plateau. The gravity meter that had rolled in on the speed pallet was extremely stable. At the South Pole, Skier 95 offloaded fuel while the IcePod team made a quick trip to the actual pole.
The flight was a success – data collected on an opportune flight and fuel delivered.
For more on the IcePod project: http://www.ldeo.columbia.edu/res/pi/icepod/