By late spring 1989, equipment was on the ice in Greenland to begin a project that would last the next five spring-summer seasons, led by Paul Mayewski, an internationally recognized leader in climate change research who now serves as director of the Climate Change Institute at the University of Maine. The National Science Foundation’s Greenland Ice Sheet Project 2, or GISP2, involved 25 universities working together to develop new techniques for extracting information from the longest ice cores ever taken from the planet’s harshest environments. GISP2 retrieved the longest continuous ice core record collected to date from the Northern Hemisphere, and the most detailed on Earth. A massive drill chewed its way through the glacier for just under two miles until it hit rock that hadn’t been disturbed for perhaps 400,000 years. The project’s amazing frozen records document 100,000 years of climate history with evidence of major environmental events such as volcanoes and forest fires. They also reveal the dramatic influence that humans have had on the chemistry of the atmosphere and climate change through substantial additions of greenhouse gases, acid rain and stratospheric ozone depletion.

Ice cores indicate that changes in climate over the last 100,000 years have been produced by several different agents, such as Earth’s orbital cycles of eccentricity (greater than 70,000 years), obliquity (38,500 years) and precession (22,500 + 11,100 years) and that dramatic change in the chemistry of the atmosphere has occurred over the last century due to human activity. Other cycles were found to be related to ice sheet dynamics, ocean circulation and solar variability.

Change of Greenland Ice Sheet

The total volume of land-based ice in the Arctic has been estimated to be about 3,100,000 cubic kilometers, which corresponds to a sea-level equivalent of about eight meters. Most glaciers and ice caps in the Arctic have been in decline since the early 1960s, with this trend speeding up in the 1990s. The Greenland Ice Sheet dominates land ice in the Arctic.

The extent of seasonal surface melt on the Greenland Ice Sheet has been observed by satellite since 1979 and shows an increasing trend, with the total area of surface melt on the Greenland Ice Sheet breaking all records in 2002. In addition to contributing to the rise of sea levels worldwide, this process adds freshwater to the ocean, with potential impacts on ocean circulation and, in turn, regional climates.

How glaciers record climate

Greenland’s massive ice sheet, (Antarctica’s ice sheet is the only other one) is the result of thousands of years of falling and compacting snow. And when snow falls on an ice sheet, it carries with it the dust and chemicals from the atmosphere.

Consequently, the ice sheet has preserved, in small air pockets, samples of the atmosphere’s chemistry from those times before direct records were taken, storing them in sequential layers. GISP2 ice core samples allow us to view a 110,000-year-long climate record from times before we were able to measure it, allowing us to study the relation between greenhouse gases and climate in the past.

Acid Rain precursors in the atmosphere revealed in the GISP2 ice core

The GISP2 record has shown a dramatic increase in both nitrate and sulfate, major components of acid rain, during the 20th century relative to the past 1,000 years. Changes in sulfate are closely tied to industrial activity in North America and Europe: the beginning of the Industrial Revolution, the Great Depression, World War II, the period of most intense burning of sulfur-rich ‘dirty’ coal, and the beginning of the Clean Air Act. Most of the short-term (up to 1-2 years) increases in sulfate that were observed were the product of volcanic activity, such as the Tambora eruption of 1815 and the Laki eruption of 1773.

From GISP2 it was determined that the Chernobyl nuclear accident released radioactive fallout that spread throughout the Arctic and high latitudes of the Northern Hemisphere.