A perspective on ancient Antarctic (blue) ice

The Antarctic ice sample record, collected since the 1960s, covers the past 1.2 million years continuously, and contains discontinuous “snapshots” up to 6 million years. Over 40 Antarctic ice cores have vastly advanced the understanding of past climate variations and will continue to tackle key paleoclimate question in the coming decades.

To obtain and further refine the discontinuous record older than 1.2 million years, ongoing efforts are targeting so-called blue ice areas. In these areas, complex ice flow patterns can trap extremely old ice, as demonstrated in the Allan Hills region (Transantarctic mountains). However, these complex flow patterns pose challenges in the search for and interpretation of ancient ice. To overcome these challenges and further unlock this paleoclimatic archive, blue ice research advances with: (i) systematic surface dating as a preliminary step to drilling; (ii) improving the understanding of age relationships between ice, dust, and meteorites; (iii) developing models that account for the specific physical properties of blue ice to identify and characterize the oldest trapped ice; and (iv) methods for the reconstruction of the paleoclimate signals preserved within this archive. In this perspective, we discuss past and current blue ice projects and contextualize the findings in the Antarctic paleoclimate record.