Since continuous meteorological and oceanographic data for the Fram Strait reach back only 150 years, the team drilled ocean sediment cores dating back 2,000 years to determine past water temperatures. The researchers used microscopic, s ed protozoan organisms called foraminifera -- which prefer specific water temperatures at depths of roughly 150 to 650 feet -- as tiny thermometers.
In addition, the team used a second, independent method that involved analyzing the chemical composition of the foraminifera s s to reconstruct past water temperatures in the Fram Strait, said Marchitto.