« Horizontal coring » in blue ice areas of Antarctica: an accessible approach for assessing paleoclimate variations

Reconstructing past Antarctic climate typically relies on vertical drilling of deep ice cores. However, the ~1% of the Antarctic ice sheet exposes blue ice, which offers a unique resource for paleoclimate research. The typically old blue ice exposed at the surface presents a continuous horizontal age gradient. By sampling ice along a transect in blue ice, we can thus reconstruct past climate variations.

In this study, we treat surface blue ice transects as horizontal ice cores and analyze 444 ice samples from the Sør Rondane Mountains. Isotope (δ18O) measurements from these samples enable the estimation of surface paleotemperatures for both the current interglacial period and the Last Glacial Maximum. By combining these paleotemperatures with the spatially variable source elevations of the blue ice, we provide the first insights into the (absence of) lapse rate changes (variations in the elevation-temperature relationship) in Antarctica over the last deglacial warming.

The absence of lapse rate changes in the samples from Antarctica contrasts with lower latitudes, which have experienced elevation-dependent warming over the same period. Our results reaffirm the potential of blue ice as an archive for reconstructing past climatic variations in Antarctica, and the easily accessible samples offer complementary insights to those obtained from vertical ice core drilling.