Online seminar by Prof. Raymond Bradley from University of Massachusetts
12 May 2021
KST 09:30 – 10:30
Multidecadal variations in North Atlantic sea surface temperatures are linked to areas far beyond that region, via atmospheric teleconnections. We take advantage of one such linkage, to reconstruct multi-decadal variations of Atlantic SSTs (AMV or AMO) using an annually laminated sediment record that spans the last 2900 years. Our record shows a persistent multi-decadal signal which correlates well with paleoceanographic proxies. It shows that North Atlantic SSTs were coldest in the main phase of the Little Ice Age (LIA) from ∼1400–1800 CE whereas today they are among the warmest of the past 3 millennia.
The LIA was preceded by an exceptional intrusion of warm Atlantic water into the Nordic Seas in the late 1300s causing the break-up of sea-ice and calving of tidewater glaciers. This warm water intrusion was a consequence of persistent atmospheric blocking over the North-Atlantic, linked to exceptionally high solar activity at that time. Weakening of the blocking anomaly in the late 14th century allowed the large volume of ice that had accumulated in the Arctic to be exported into the North Atlantic, leading to a weakening of the AMOC, setting the stage for the subsequent LIA.