Marine climate variability during the last millennium: The Loch Sunart record, Scotland, UK

The first decadal-scale reconstruction of British coastal temperature anomalies spanning the last millennium is presented from a sea loch (fjord) basin, Loch Sunart, NW Scotland. Based on modern observation and the results of previous numerical modeling of fjord circulation, benthic foraminiferal oxygen isotope records are interpreted as a record of summer temperature. A significant climate transition, apparently driven by large-scale reorganization of northern Hemisphere atmospheric circulation, occurs in the record around AD 1400. An abrupt, but relatively short-lived climate warming occurs between AD 1540–1610, when the bottom water temperature anomalies are 1.1 °C above the long-term average, which is warmer than most of the 20th century and the late Medieval Warm Period. A long-term cooling occurs throughout the Little Ice Age culminating in the coldest recorded temperature anomalies between the late 1920s and 1940s. The warmest reconstructed temperatures of the past millennium occurred in the last 5 years of the record, which ends in 2006. A replicated post-AD 1900 shift in benthic foraminiferal δ13C of ca −0.6‰ provides evidence of the Oceanic δ13C Suess Effect; this feature provides an independent test of the age model and demonstrates the value of benthic foraminifera as palaeo-proxies in the Loch Sunart record.