Granulometry of two sediment cores from Maxwell Bay, South Shetland Islands, West Antarctica

The climate evolution of the South Shetland Islands during the last c. 2000 years is inferred from the multiproxy analyses of a long (928 cm) sediment core retrieved from Maxwell Bay off King George Island. The vertical sediment flux at the core location is controlled by summer melting processes that cause sediment-laden meltwater plumes to form. These leave a characteristic signature in the sediments of NE Maxwell Bay. We use this signature to distinguish summer and winter-dominated periods. During the Medieval Warm Period, sediments are generally finer which indicates summer-type conditions. In contrast, during the Little Ice Age (LIA) sediments are generally coarser and are indicative of winter-dominated conditions. Comparison with Northern and Southern Hemisphere, Antarctic, and global temperature reconstructions reveals that the mean grain-size curve from Maxwell Bay closely resembles the curve of the global temperature reconstruction. We show that the medieval warming occurred earlier in the Southern than in the Northern Hemisphere, which might indicate that the warming was driven by processes occurring in the south. The beginning of the LIA appears to be almost synchronous in both hemispheres. The warming after the LIA closely resembles the Northern Hemisphere record which might indicate this phase of cooling was driven by processes occurring in the north. Although the recent rapid regional warming is clearly visible, the Maxwell Bay record does not show the dominance of summer-type sediments until the 1970s. Continued warming in this area will likely affect the marine ecosystem through meltwater induced turbidity of the surface waters as well as an extension of the vegetation period due to the predicted decrease of sea ice in this area.

Chronology for the EDML ice core from Dronning Maud Land, Antarctica, over the last 150 000 years

A chronology called EDML1 has been developed for the EPICA ice core from Dronning Maud Land (EDML). EDML1 is closely interlinked with EDC3, the new chronology for the EPICA ice core from Dome-C (EDC) through a stratigraphic match between EDML and EDC that consists of 322 volcanic match points over the last 128 ka. The EDC3 chronology comprises a glaciological model at EDC, which is constrained and later selectively tuned using primary dating information from EDC as well as from EDML, the latter being transferred using the tight stratigraphic link between the two cores. Finally, EDML1 was built by exporting EDC3 to EDML. For ages younger than 41 ka BP the new synchronized time scale EDML1/EDC3 is based on dated volcanic events and on a match to the Greenlandic ice core chronology GICC05 via 10Be and methane. The internal consistency between EDML1 and EDC3 is estimated to be typically ~6 years and always less than 450 years over the last 128 ka (always less than 130 years over the last 60 ka), which reflects an unprecedented synchrony of time scales. EDML1 ends at 150 ka BP (2417 m depth) because the match between EDML and EDC becomes ambiguous further down. This hints at a complex ice flow history for the deepest 350 m of the EDML ice core.