Snowmelt uncovers ancient penguin colony | Polarjournal
The site where the colony was found is situated at Cape Irizar, a rocky area south of the Drygalski Glacier tongue on the Scott Coast in the Ross Sea. Since Robert Falcon Scott had discovered this area, no Adélie penguin colony had been ever recorded here. Photo: Steven D. Emslie

Adélie penguins are the most southern breeding penguin species. Their colonies, which are located along the coast of the Antarctic continent and on some nearby islands, often consist of tens of thousands to hundreds of thousands of animals. However, the animals characteristic of Antarctica need snow-free and stony areas in order to be able to build their nests. It is probable that not all colonies have yet been discovered and described. Now, in a study funded by the National Science Foundation and the US Antarctic Program, US researchers have discovered an ancient, previously unknown site of a colony buried under the snow of Antarctica for centuries.

Although researchers had already found penguin guano at the site in the past and dated it to an age between 4,700 and 800 years. But Steven D. Emslie, a professor of paleoecology at the University of North Carolina Wilmington, would go one step further. In 2016, a strong warming in the region had caused the snow at Cape Irizar to melt away almost completely. There were bones, feathers and even penguin mummies and fresh remains buried under the snow. Numerous stone mounds over the entire area of the cape could also be recorded, indicating that this must have been a large colony.

The remains discovered by Steven Emslie included feathers and bones, well-preserved penguin mummies and even “fresh” bodies of chicks and adult animals. Analysis showed that the youngest carcasses were only 800 years old, others several thousand years old. Photo: Steven D. Emslie

“Overall, our sampling recovered a mixture of old and what appeared to be recent penguin remains implying multiple periods of occupation and abandonment of this cape over thousands of years.”

Professor Steve D. Emslie, University of North Carolina Wilmington

An examination of the remains showed that the colony had existed for a long time and had only been occupied about 800 years ago. “We excavated into three of these mounds, using methods similar to archaeologists, to recover preserved tissues of penguin bone, feather, and eggshell, as well as hard parts of prey from the guano,” explains Steven Emslie. “Overall, our sampling recovered a mixture of old and what appeared to be recent penguin remains implying multiple periods of occupation and abandonment of this cape over thousands of years.” The researcher suspects that with the onset of the Little Ice Age, which had lasted until the mid-19th century, a constant snow cover had rendered the place unusable for the Adélies. However, the youngest remains had been ideally preserved.

Adélie penguins build their nests from stones, which they raise to small mounds. Precipitation and humidity cannot accumulate and the eggs stay dry. But this type of nest-building reduces the location of colonies to certain areas that are snow-free in summer. Picture: Michael Wenger

The experienced paleoecologist Emslie never before encountered a similar collection of such remains from different ages. Since the 1980s, the average temperature in the Ross Sea region has risen by more than 1.5°C. Thus, the massive snow cover that had covered Cape Irizar for centuries has become thinner and thinner. “This recent snowmelt revealing long-preserved remains that were frozen and buried until now is the best explanation for the jumble of penguin remains of different ages that we found there,” he says. The progressive warming of Antarctica is expected to uncover more paleontological treasures like this.

Dr Michael Wenger, PolarJournal

Link to the study: Emslie S. (2020) Geology, EPub; Ancient Adélie penguin colony revealed by snowmelt at Cape Irizar, Ross Sea, Antarctica; doi.org/10.1130/G48230.1

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