| Summary: | The PIs propose to develop a new, high-resolution (annual to sub-decadal) paleoclimate record (0-1,000 y) from sediment cores taken on the Arctic inner continental shelf. The proposal is a follow-up to a regular Arctic Natural Sciences panel submission that was criticized during review due to 1) absence of adequate data to substantiate a high-quality paleoclimate record in this setting, and 2) questions about the logistical success in light of the absence of UNOLS vessels to work in the high Arctic. Neither issue can be addressed without a proof of concept study such as proposed here. The PIs will collect sediment cores from the inner shelf on one cruise of the R/V Annika Marie, a local and privately chartered research vessel, presently scheduled for late September 2009 (ice free period) adjacent to the Colville delta on the Beaufort Sea coast of Alaska. Ancillary seismic transect data (sub-bottom CHIRP and side-scan sonar) will be collected prior to coring to locate the best preserved record of depositionally laminated sediments of this time interval. About 5 to 15 sites will be occupied on the shelf and adjacent Simpson Lagoon. All cores will be diver-collected in less than 8 m water depth: short push cores will be used to retrieve the high-porosity recent sediment layers, and longer cores (up to 5 m) will be collected with a submersible portable vibracorer. All cores will be analyzed for stratigraphy (x-radiography), bulk organic and mineral content, and geochronology of the last 100 to 200 y (using 210Pb and 137Cs radiotracers). Two cores will be selected from these for detailed analysis of paleoclimate proxies: the age-depth relationship for the deeper part of these cores will be determined using AMS radiocarbon dating of benthic foraminifera (5/core). Climate indicators that will be applied are organic biomarkers (ligninphenols, plant pigments, and รค13C) and mineral tracers (clay mineralogy, heavy mineral assemblages, granulometry, event layer stratigraphy). The central hypothesis is that the Colville inner shelf contains a high quality sediment record, that, if exploited, will dramatically improve knowledge of high Arctic paleoclimate over the last centuries to a millennia. They believe this deltaic region has sufficiently high linear sediment accumulation rates (>1 cm/y) to preserve a seasonal and interannual record of climate change-induced mineral and particulate organic carbon (POC) flux variations to the seafloor from three distinct sources. These are 1) rivers that drain the Brooks Range and the Arctic Coastal Plain (ACP), 2) coastal erosion of ACP permafrost deposits and 3) marine primary production by phytoplankton, ice algae, and benthos. After an initial micro-scale examination of recent event layer (annual and storm deposits) mineral and POC succession, necessary to interpret paleoclimate-induced fluctuations in composition, they propose to examine the downcore record of temporal variations in layers, comparing the two selected sites to decouple spatial changes in sources. Since the three end-member sources have distinct mineral/POC composition, temporal variations will provide proxy information about climate changes that influence their flux magnitude including 1) landfast ice extent, 2) river sediment supply from glacial (meltwater) and coastal plain (permafrost thawing) input, 3) summer-fall storminess and 4) primary productivity of the coastal zone.
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