Little Ice Age climate and oceanic conditions of the Ross Sea, Antarctica from a coastal ice core record

Increasing paleoclimatic evidence suggests that the Little Ice Age (LIA) was a global climate change event. Understanding the forcings and associated climate system feedbacks of the LIA is made difficult by the scarcity of Southern Hemisphere paleoclimate records. We use a new glaciochemical record of a coastal ice core from Mt. Erebus Saddle, Antarctica, to reconstruct atmospheric and oceanic conditions in the Ross Sea sector of Antarctica over the past five centuries. The LIA is identified in stable isotope (delta D) and lithophile element records, which respectively demonstrate that the region experienced 1.6 +/- 1.4 degrees C cooler average temperatures prior to 1850 AD than during the last 150 yr and strong (> 57 ms(-1)) prevailing katabatic winds between 1500 and 1800 AD. Al and Ti concentration increases of an order of magnitude (> 120 ppb Al) are linked to enhanced aeolian transport of complex silicate minerals and represent the strongest katabatic wind events of the LIA. These events are associated with three 12-30 yr intervals of cooler temperatures at ca. 1690 AD, 1770 AD and 1840 AD. Furthermore, ice core concentrations of the biogenic sulphur species MS- suggest that biological productivity in the Ross Sea polynya was similar to 80% higher prior to 1875 AD than at any subsequent time. We propose that cooler Antarctic temperatures promoted stronger katabatic winds across the Ross Ice Shelf, resulting in an enlarged Ross Sea polynya during the LIA.