BOZEMAN – A Montana State University professor is part of a nation-wide team that is publishing a new study linking past climate changes in the Arctic and Antarctic.
Renowned polar ecologist John Priscu helped write the proposal that funded the research and co-authored a paper to be published in the April 30 issue of the scientific journal, Nature.
Scientists from 28 science and engineering groups from around the United States conducted the research that was explained in the paper. By comparing ice cores from the northern and southern hemispheres, they discovered that past abrupt temperature changes at the North Pole affected the climate at the South Pole. They learned that climate changes that started in the Arctic spread to Antarctica.
“The topic is very important to understanding how climate oscillates between the north and south poles,” Priscu said. “Such information provides us with a new perspective on global climate dynamics and will help us assess future climate regimes.”
Priscu is a professor in MSU’s Department of Land Resources and Environmental Sciences in the College of Agriculture. He investigates the biogeophysics of icy ecosystems, a topic that has taken him to Antarctica for more than 30 years and the Arctic for five years.
The team that conducted the newly published study wanted to determine the relative timing of temperatures changes in the Arctic and Antarctic. Since ice cores were already available from Greenland, giving them a detailed record of temperature changes in the Arctic, they searched for a site that would give them the same type of information from the southern hemisphere.
The team considered sites all over Antarctica, but finally selected a site in West Antarctica. They determined that a field camp in the center of West Antarctica and 650 miles from the geographic South Pole was ideal for taking an ice core sample because of a combination of factors -- the thick ice, simple ice flow and annual snowfall, according to a National Science Foundation press release. The location, called WAIS Divide, receives 1.5 feet of snow a year. The ice there is 11,200 feet thick.
“When snow falls at WAIS Divide, it rarely melts, and instead builds up in thick annual layers, which are compressed into ice by subsequent snowfall,” the team said. “The compacted snow contains dust, microbes, chemicals and atmospheric gases, which are trapped in the ice. The dust, bacteria and other chemicals in the ice are indicators of past climate, and the gas contained in air bubbles is a sample of the ancient atmosphere. The deeper the ice, the older it is, and the further back in time measurements can be made.”
The team pulled out an ice core that measured 4.8 inches in diameter and 11,200 feet long. After comparing it to ice cores from the northern hemisphere, the scientists said that the climate in Greenland was unstable during the last ice age, with large and abrupt changes in mean annual temperature. These so-called Dansgaard-Oeschger events lasted a few thousand years, but they started and ended in just a few decades.
Temperature changes in Antarctica followed an opposite pattern, however. Antarctica was cooling when Greenland was warm, and vice versa. The new work shows the abrupt climate changes started in the North Atlantic around Greenland. It then took about 200 years for ocean currents to redistribute the heat to Antarctica.
Those past climate changes are different from what is happening today, according to the research team. The abrupt climate changes during the ice age were regional and caused by large-scale changes in ocean circulation that were triggered by the collapse of ice sheets. The current changes in temperature and precipitation are global and primarily caused by increasing levels of carbon dioxide in the Earth’s atmosphere.
“Nevertheless, understanding how and why climate changed in the past is important because it helps scientists predict how Earth’s climate will respond to human-caused increases in greenhouse gases,” the team said.
The recent study resulted from the work of several groups within the research team. An engineering team from the University of Wisconsin-Madison designed the ice coring drill and recovered the ice core. The Desert Research Institute in Nevada, along with the University of New Hampshire, coordinated the science, drilling and logistics activities. The National Ice Core Laboratory in Colorado led the sampling and archiving of the ice core. The past temperatures were determined by measuring the isotopes of the melted ice at the University of Washington. The relative timing of the changes was determined by Oregon State University by using variations in the atmospheric concentration of methane to synchronize the timing of measurements from the Greenland and Antarctic ice cores. Other climate conditions were determined with chemical and particle measurements in the ice made by the Desert Research Institute.
Priscu’s team has shown that bacteria in the ice core track major climatic events and can tell us what life was like during these events.
Nature is an international weekly journal for all fields of science and technology.
Evelyn Boswell, (406) 994-5135 or firstname.lastname@example.org