Bookends on Ice: North-South Glaciers
Date: April 11, 2002
Offer Clues To Global Climate Change
By: Chris Curran
Phone: (513) 556-1806
Images courtesy: Thomas Lowell, UC geology
Archive: Research News
Twelve years of climbing, coring, and collecting evidence of climate change across the Southern Hemisphere are leading to a new understanding of global climate change and attracting the attention of top climate scientists
UC geology professor Thomas Lowell began working in Chile in 1990 and added New Zealand to his field studies in 1997, as part of an international research team looking at glacial retreats and advances over the last 25,000 years.
The evidence collected over those 12 years demonstrates that glaciers in the Southern Hemisphere changed in sync with Northern Hemisphere glaciers on three different time scales: the end of the last major Ice Age (14-15,000 years ago), a period of abrupt climate change known as the Younger Dryas cold reversal (10-11,000 years ago) and the Little Ice Age which lasted from the 14th to the 19th centuries A.D.
That's strong evidence that changes in the atmosphere and not the oceans are the driving force for global climate change, but it's far from the end of the research effort.
Lowell recently returned from a two-month field season and climate change meeting on New Zealand's South Island. The research team in New Zealand included UC senior Janelle Sikorski, George Denton and Colby Smith of the University of Maine, Bjorn Andersen of the University of Oslo in Norway, and Chris Hendy of the University of Waikato in New Zealand.
The team's goal is to understand how Earth's climate has changed in the past and how abruptly it might change in the future. "For example, for the end of the Little Ice Age, the key question is, 'When did the human influence kick in?' Our work will help set up the baseline to address that question," explained Lowell, adding that 12 years of fieldwork isn't nearly enough.
"The need for more work is clear. The largest debate now is when the human influence overtook the natural warming." So, it will be important to find out if warming events prior to the Little Ice Age were larger or smaller than the present global warming.
Dating the glacial changes in the Southern Hemisphere is difficult for many reasons, including the lack of historical records. The Little Ice Age is Europe, on the other hand, is very well documented because of the large population living there at the time.
So, the researchers rely on a number of tools to determine where the glaciers were and when they melted away. The techniques include coring lakes to find sediment records, radiocarbon dating, lichenometry (tracking the size and number of lichens growing on exposed rocks) and analyses of the exposed rocks themselves. The thoroughness has paid off by overturning some previous studies and interpretations.
"We continually discover many reconnaissance studies uncover certain aspects of the chronology correctly, but lack in other details," explained Lowell. "Our philosophical approach is somewhat different in that we often investigate areas where the work seems to have been already well established, but our investigations continually add new detail and insights."
The work in Chile continued through 1998. The first large-scale fieldwork in New Zealand began in 1997 and has focused primarily on the drier eastern side of the Southern Alps.
The researchers plan to return to New Zealand next year to begin detailed studies of the wetter, western slopes. That will allow them to add yet another tool to their dating techniques. With more water comes more trees. So, tree ring analysis should provide a clear and consistent series of dates and climate information.
Within the next three years, the team hopes to return to South America to look at Little Ice Age changes and older glacial advances along the Beagle Channel where Charles Darwin once traveled.
The work is funded by NOAA.