The study, with the participation of Dr. Carina Lange, IDEAL Center researcher, shows that ice coverage from the glaciers of the Darwin Mountain Range retreated just over 14,300 years ago.

Sediment collection aboard the icebreaker.

The main objective of the research of this group of scientists was to reconstruct fluctuations in glacial coverage of Almirantazgo Sound, a fjord located in western Tierra del Fuego, in the Magallanes and Chilean Antarctic Region.

Collaborators for this study came from the Center for the Dynamic Research of High Latitude Marine Ecosystems (IDEAL) of the Universidad Austral de Chile, South-Austral COPAS of the Universidad de Concepción, University of Ghent (Belgium), Woods Hole Oceanographic Institution, and University of Houston.

In 2005, the “Chilean Inland Passage” expedition was carried out on board the American icebreaker, Nathaniel Palmer. One area studied for geological and paleoclimate purposes included Almirantazgo Sound and Ainsworth Bay, near the Marinelli glacier, where several sediment cores (5-13 meters long) were collected. The cores were sampled with different objectives: some were used exclusively for geological analyses whereas others were also analyzed for chemical and biological purposes. After being described, reviewed, and sub-sampled on board, the cores were sent to various specialized laboratories.

“In high latitude Southern Hemisphere paleoclimate studies, one of the key questions is when deglaciation occurred in the Chilean Patagonia, which is when the great Patagonian ice cap melted resulting in the formation of the ice fields observed today: Campo de Hielo Norte, Campo de Hielo Sur, and Campo de Hielo Cordillera Darwin,” explains IDEAL Center and South-Austral COPAS researcher, Dr. Carina Lange.

The collaborative research showed that Almirantazgo Sound began to lose its ice cover over 14,300 years ago.

“Since that date, and through a series of advances and retreats in the ice coverage, sedimentological analyses indicate that starting 12,300 years ago, the area was transformed into an open environment, and as of 9,800 years ago it became what we know today as Almirantazgo Sound, a predominantly saline fjord,” says Dr. Lange.

The researchers detected advances and retreats from that date in the area of the glaciers making up part of the Darwin Mountain Range as a result of various natural global changes that occurred in the Holocene, beginning approximately 11,000 years ago.

“The Darwin Mountain Range is made up of hundreds of glaciers. The largest is the Marinelli glacier, which is the most studied given its great retreat in recent decades,” says Dr. Lange.

Researcher Dr. Carina Lange.

In parallel, the study revealed two major melting events in the last 3,200 years. “These events, which indicate rapid glacial retreat, negatively affected marine productivity and changed the salinity of Almirantazgo Sound, reflecting the freshening effect on the waters of the fjord,” concludes Dr. Lange.

These scientific results highlight the potential of fjord sediments to act as paleoclimate archives for high resolution reconstructions of past glacier variability on a scale of hundreds to thousands of years.