Climate Evolution of the Antarctic Peninsula Over the Last 1,000 Years : An Environmental Magnetism Analysis of Two High Resolution Sediment Cores

Two marine sediment cores from very different depositional environments, off the coast of western and northeastern Graham Land, Antarctic Peninsula (AP), record high resolution climatic records of the last 1,000 years. This study finds evidence in the sedimentary magnetic signature for a regional shift from warmer to colder climatic conditions around 1100-1400 AD. The first core, from middle Barilari Bay, western AP, displays a shift from seasonally open marine conditions to sub/proximal ice shelf ca. 1100 AD, with evidence for multiple grounding line advances in the magnetic mineral distributions during the first half of the last millennium. Prior to the glacial advance ca. 1100 AD, middle Barilari Bay was characterized by high primary productivity with pulses of ice rafted debris atypical of the fjord’s local geology. The second core, from Perseverance Drift, north of Joinville Island, northeastern AP, contains a change in the magnetic mineral assemblage ca. 1350 AD, interpreted as a reflection of higher-than-modern pore water sulfide concentration driven by decreased bioturbation and limited exchange between sediment pore water and ocean water. These events are interpreted as expressions of a regional Little Ice Age like event on the AP and indicate these study sites as prime locations for investigation of AP climate evolution over the last millennium leading to the abrupt climatic changes observed in recent history