GOING TRANSATLANTIC: SPATIAL VARIATIONS IN LATE HOLOCENE SEA-LEVEL CHANGE

Sea-level changes record mass balance changes of ice sheets and mountain glaciers, as well as dynamic ocean-atmosphere processes. Unravelling the contribution of each of these mechanisms requires observations from more than one location or coastline and, ideally, from a number of sites on several coasts within one or more oceans. Satellite measurements provide a global picture of sea level over the last decade and tide gauge extend these records back in time by more than 200 years at some locations. However, we need even longer records if we are to make sense of the processes that drive these time series and establish whether changes at a single site reflect local or more regional processes.

We present new, 2000 year-long records of relative sea-level (RSL) change from two salt marshes in north west Scotland. Because these sites record long term (Holocene) uplift we identify accelerations in sea level against a background trend of RSL fall. This contrasts with many existing late Holocene RSL records that are from subsiding sites where RSL accelerations are potentially harder to define. We develop precise chronologies using bomb spike ¹⁴C, AMS ¹⁴C, ¹³⁷Cs, ²¹⁰Pb, stable Pb isotopes, pollutant histories and pollen records. We compare our results with RSL records from elsewhere around the North Atlantic (USA eastern seaboard, Iceland, western Europe). Our Scottish data do not show as pronounced early 20^th century acceleration in RSL as observed at sites on the eastern US seaboard, demonstrating an important spatial difference across the North Atlantic basin. Prior to this acceleration, rates of RSL change along the European coast (corrected for glacio-isostatic adjustment) are generally smaller than those observed along the USA coast. These spatial patterns are compatible with mass balance changes in the Greenland Ice Sheet, as well as dynamic ocean processes within the North Atlantic.