“These ice cores provide the longest and highest-resolution tropical ice core record to date,” said Lonnie Thompson, distinguished university professor of earth sciences at OSU. “In fact, having drilled ice cores throughout the tropics for more than 30 years, we now know that this is the highest-resolution tropical ice core record that is likely to be retrieved.”
Drilled from Peru’s Quelccaya Ice Cap, the new cores are especially important because most of their 1,800-year history exists as clearly defined layers of light and dark. The light is a result of accumulated snow of the wet season, while the dark is from dust accumulated over the dry season.
Another reason they are special is the location where they formed, atop the high Andean altiplano in southern Peru. Snowstorms fueled by moist air rising from the Amazon Basin east of the ice cap provide most of the moisture of the region. The west also affects these ice core-derived climate records from the Andes in the form of El Nino, a temporary change in climate, which is driven by sea surface temperatures in the tropical Pacific.
El Nino is recorded in the Quelccaya ice cap as a chemical signature (especially in oxygen isotopes) that indicates sea surface temperatures in the equatorial Pacific Ocean over much of the past 1,800 years.
“We have been able to derive a proxy for sea surface temperatures that reaches back long before humans were able to make such measurements, and long before humans began to affect Earth’s climate,” Thompson said in a statement.