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The skull of an adult male southern elephant seal sits on a desk in a small office on the University of Maine campus in Orono. It is a large skull, about a foot and a half long if it were all in one piece.
The seal was discovered intact, mostly frozen, in the soil of Antarctica. It was about 14 feet long and would have weighed 2 to 3 tons or more. The skull and the skeleton it belongs to are probably at least 1,000 years old, but tests are still being done to determine its age.
Most of the skull is a brownish-tan color, including the teeth, one of which was broken, perhaps in a fight. A portion of the lower jaw had been protruding from the ground, and it, along with two large teeth, was bleached white by the Antarctic sun.
The skull is fragile, and Dr. Brenda Hall handles it gently and only occasionally.
Hall discovered the remains of the southern elephant seal almost a decade ago on the western shore of the Ross Sea in Antarctica while conducting research into the history of the Ross Ice Shelf. That accidental discovery has shed new light on the stability of Antarctic ice sheets and could provide clues for scientists as they piece together the puzzle of global climate change.
The presence of the seals in the Ross Sea, a section of the continent that today is too cold to support them, is an indication that climate in that area has changed in the past 7,000 years and that the area was once warmer than it is today.
Hall, a glacial geologist at the University of Maine, discovered tiny bits of elephant skin and fur while conducting research into the history of the Ross Ice Sheet. She was attempting to determine the age of raised beaches along the Victoria Land coast by radiocarbon dating of organic matter found there.
“The Antarctic is a bad place to date things,” Hall said. “There’s not much organic material there. We spend a lot of time on our hands and knees, turning over stones. We’ll find small fragments, usually shell fragments.”
The skull segment is surrounded by other pieces of bone, some with sections of skin and fur still attached, as well as plastic bags containing shells, moss and lichen collected from the Ross Sea shores.
During one of her research expeditions, Hall discovered the small fragments of what she later learned was elephant seal fur still attached to skin. Initially, she said, she thought the tiny pieces might be seaweed. She points to a vial containing a sample about an inch long. That, she said, is a large sample.
It took about six years to positively identify those initial specimen items, she said. But in subsequent visits, Hall and her colleagues have discovered more elephant seal remains, including complete seals, some mummified in the Antarctic sun, and others, such as the specimen in her office, frozen into the barren coastline. Some of the remains are as much as 7,000 years old and likely come from ancient breeding and molting grounds.
Hall and a group of colleagues in the United States, Great Britain and Italy recently published their findings in the Proceedings of the National Academy of Sciences. They point to the presence of the seals as evidence of two warming periods in that section of the Antarctic during the past 7,000 years, one about 4,500 to 6,000 years ago, the other about 1,000 to 2,300 years ago.
The elephant seals are an indicator of those warming periods, Hall said, because they need to have open water near the shore. Although most of their lives is spent in the water, they do come ashore for extended periods for breeding and during the molting season.
“Today that coast has sea ice along it,” Hall said. “It’s very thick, perennial ice, land-fast ice right up to the land and grounded on the sea floor. The elephant seals prefer completely open water.”
Based on findings over the past 10 years, Hall said it appears there were periods when the sea ice was less extensive in the area, which would have provided the open water the elephant seals need. Collaborative studies have looked at the remains of Adelie penguins, which need pack ice to survive. Although the seals and the penguins sometimes occupied the coastline at the same time, during most of the times when the penguins thrived, the seals were absent. When the elephant seals were present, the penguins disappeared.
The importance of the discovery relates to current concerns over global warming and the anticipated rise in sea levels if the Antarctic ice sheets break up, said Hall, who is an assistant professor of glacial geology and Quaternary studies and also works at the university’s Climate Change Institute.
Evidence already exists of weakening in some areas of some ice sheets, she said.
The massive Western Antarctic Ice Sheet is thought to be unstable. Some scientists maintain that the Ross Ice Sheet is holding it in place and keeping it from dumping out into the ocean. If the Western sheet broke off into the ocean, it could raise sea levels around the world by as much as 20 feet, Hall said.
“By studying that ice shelf, we may be able to set parameters on how much warming the ice shelf can take,” she said. “We know that there is no evidence the ice shelf disappeared while the elephant seals were present. So we know it survived warmer than present climates. We don’t know how much warmer yet.”
Hall’s study is one of many that are looking at Arctic and Antarctic regions in an effort to understand global climate change and how human activity is affecting natural cyclical changes in the Earth’s climate.
“The climate does change,” she said. “We’d like to know what causes that natural variability, what triggers it.”
If they can understand the natural cycles that affect global climate changes, she said, scientists then may be able to understand better the impact human activity is having on climate.
Hall expects to be back in the Antarctic in December to continue her investigation of the ice sheets and the elephant seals.
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