The Cryosphere, March 18
Sediment at the bottom of the Camp Century ice core, collected 120 km from the coast in northwestern Greenland, reveals that Greenland fully melted and re-formed at least once in the past 1.1 million years; possibly as recently as 400,000 years ago. This might mean that the Greenland ice sheet is more sensitive to temperature rise than previously thought, as it was assumed Greenland last melted completely during the somewhat warmer Pliocene (over 3 million years ago). This sedimentary time capsule, frozen under nearly 1.4 km of ice, contains the well-preserved fossils of plants and biomolecules sourced from at least two ice-free warm periods since the Pleistocene, nearly 2 million years ago; with at least two episodes of ice-free, vegetated conditions, each followed by glaciation. CO2 levels never exceeded 300 ppm during this period, and temperatures remained within 2 degrees above pre-industrial. Understanding the history of the Greenland ice sheet is critical for predicting its response to future climate warming and contribution to sea-level rise.
Compiled by Amy Imdieke