Inorganic carbon and geochemistry measurements from landfast sea ice in Resolute Passage, Nunavut, Canada, as part of the Arctic-ICE project, May - June 2010

We conducted a six-week investigation of the sea ice inorganic carbon system during the winter-spring transition in the Canadian Arctic Archipelago. Samples for the determination of sea ice geochemistry were collected in conjunction with physical and biological parameters as part of the 2010 Arctic-ICE (Arctic - Ice-Covered Ecosystem in a Rapidly Changing Environment) program, a sea ice-based process study in Resolute Passage, Nunavut. The goal of Arctic-ICE was to determine the physical-biological processes controlling the timing of primary production in Arctic landfast sea ice and to better understand the influence of these processes on the drawdown and release of climatically active gases. The field study was conducted from 1 May to 21 June, 2010.

Geochemistry on smectites in sediment cores CRP-1 and CRP-2 from the Ross Sea, Antarctica

TEM (transmission electron microscopy) observations and microanalyses on smectite microparticles in the sediments of the CRP-2A core were carried out to determine their origin (authigenic or detrital) and the source rocks. Smectites are dioctahedral and are Fe-rich members of the nontronite-beidellite series. They generally display both flaky and hairy shapes, but no large compositional difference between the two forms was observed. Flaky smectites are detrital while hairy smectites probably formed in situ through the reorganisation of previous flaky particles. The source rocks for smectites are probably represented by the McMurdo Volcanic Group to the south, but also by the Ferrar Dolerites and Kirkpatrick Basalts in the Transantarctic Mountains. CRP-2A smectites are Fe and Mg richer than those of the coeval or not coeval levels of the CIROS-I, DSDP 270 and 274 cores. The average compositions of smectite in CRP-1 and CRP-2A cores show a downcore trend toward more alluminiferous terms, which might reflect the increase of the chemical weathering processes on the continent.

Nd-Sr isotopes, diatom and biogenic opal content of Pliocene sediments from IODP Site 318-U1361

Warm intervals within the Pliocene epoch (5.33-2.58 million years ago) were characterized by global temperatures comparable to those predicted for the end of this century (Haywood and Valdes, doi:10.1016/S0012-821X(03)00685-X) and atmospheric CO2 concentrations similar to today (Seki et al., 2010, doi:10.1016/j.epsl.2010.01.037; Bartoli et al., 2011, doi:10.1029/2010PA002055; Pagani et al., 2010, doi:10.1038/ngeo724). Estimates for global sea level highstands during these times (Miller et al., 2012, doi:10.1130/G32869.1) imply possible retreat of the East Antarctic ice sheet, but ice-proximal evidence from the Antarctic margin is scarce. Here we present new data from Pliocene marine sediments recovered offshore of Adélie Land, East Antarctica, that reveal dynamic behaviour of the East Antarctic ice sheet in the vicinity of the low-lying Wilkes Subglacial Basin during times of past climatic warmth. Sedimentary sequences deposited between 5.3 and 3.3 million years ago indicate increases in Southern Ocean surface water productivity, associated with elevated circum-Antarctic temperatures. The geochemical provenance of detrital material deposited during these warm intervals suggests active erosion of continental bedrock from within the Wilkes Subglacial Basin, an area today buried beneath the East Antarctic ice sheet. We interpret this erosion to be associated with retreat of the ice sheet margin several hundreds of kilometres inland and conclude that the East Antarctic ice sheet was sensitive to climatic warmth during the Pliocene.