The recording of the earth’s climate over the last 100,000+ years on the Greenland Ice Sheet is becoming increasing revealed during the recent extreme melting and thinning over the past ~10 years.
NASA aircraft and satellite images have recorded quantitatively and qualitative changes on the ice sheet and the landscapes that underlie the ice. These measurements and images have captured the exposure of basal, old ice along the margins, and the presence of dust layers that represent different climate periods (Picture). This climate record in the dust layers have been validated by other means, including the stratigraphy of the isotopic record in the ice (δ18O, δ2H, and d-excess) that serve as independent validation as to whether a layer is reflecting a warm or cold period.
These observations contribute to the growing body of evidence that today we are in an unprecedented warming period. And, that the Greenland Ice Sheet is thinning and melting dramatically leading to a freshening of the surrounding ocean, that alters food webs and leading to sea level rise.
MacGregor JA, Fahnestock MA, Colgan WT, Larsen NK, Kjeldsen KK, Welker JM (2020). The age of surface-exposed ice along the northern margin of the Greenland Ice Sheet. Journal of Glaciology, https://doi.org/10.1017/jog.2020.62
This picture (complements of J Sonntag) along the NW coast of Greenland captures the island-wide thinning and melting with basal ice (in this case ~55,000 years old) directly on top of the landscape and the gradation along the slope of the ice layers that lead to the surface of the ice sheet today. The banding, or stratigraphy is marked by major dust depositional periods (surrogates for global drought & warm periods) that are validated by independent water isotope (δ18O, δ2H, and d-excess) measurements (Welker’s lab).
Last updated: 31.8.2020