Surface sediments from the Chesapeake Bay and Greenland Fjords
Sediment samples from the Baltic Sea, Chesapeake Bay, USA, and two Greenland Fjords were collected for DNA and alkenone analyses (Table S1). Surface sediment samples were collected across the Baltic Sea from Skagerrak to the Bothnian Sea during expeditions M86/1 (R/V Meteor; November 2011), P435 (R/V Poseidon; June 2012), 6EZ1215 (R/V Elisabeth Mann Borgese; July 2012), EMB046 (R/V Elisabeth Mann Borgese; May 2013) through multi- corer 43. Surface sediment samples were collected in the Chesapeake Bay from July-September 2017 and kept frozen prior to DNA extraction. Two sediment cores (POR13_05 and POR13_08) from Upernavik Fjord were collected in August 2013 onboard R/V Porsild with Rumohr corer 18. One surface sediment sample from Kangerlussuaq Fjord was collected during JR106 (James Clark Ross; 2004).