Talk by Martin Miles – Københavns Universitet

Talk by Martin Miles

Martin Miles, UiB Bergen, Norway

The East Greenland Ice: New history of the past millennium

The East Greenland Ice (Koch, 1945) is the immense belt of Arctic sea ice transported along the East Greenland Current (EGC) and its downstream extension along SW Greenland, where it is termed Storis. This represents the Earth’s largest pathway of sea ice and freshwater transport, with linkages to ocean circulation and climate-system variability. Here we synthesize historical and paleo proxy records to study two aspects of the natural variability of the East Greenland Ice: (1) multidecadal variability of sea ice in a multi-century context, and (2) constraining and understanding modulations during the past millennium, focused on the onset of the Little Ice Age.

First, we integrate and synthesize a set of multi-century historical records of sea ice, and establish a signal of pervasive and persistent multidecadal (60–90 year) fluctuations that is most pronounced in the Greenland Sea, and weakens further away. We highlight evidence for co-variability between sea ice and the Atlantic Multidecadal Oscillation (AMO) during the instrumental and historical record; similar covariability through previous centuries is evident from comparison of the longest historical records and proxy reconstructions of sea ice and the AMO.

Second, we present a multi-proxy study focused on constraining and understanding modulations during the past millennium. This is addressed through a synthesis of data records spanning the length of the extended EGC pathway. These are derived from marine sediment cores and are indicative of sea-ice and ocean conditions based on multiple proxies, including direct sea-ice proxies (IP25) and indirect indicators (mineralogical and biological indicators, e.g., foraminifera and diatoms). We find reasonable coherence between the disparate records, particularly in the early 1300s – around the abrupt onset of the Little Ice Age in this region. Markedly enhanced export of sea ice from the Arctic Ocean can be inferred as a statistically extreme anomaly apparent not only along SW Greenland, but also upstream through the entire EGC pathway from the Arctic Ocean. Finally, we compare the sea ice–ocean records with atmospheric (temperature and circulation indices) and other reconstructions. It is apparent that the changes in the East Greenland ice–ocean conditions occurred decades before well-documented changes in large-scale atmospheric circulation around the early 1400s.