| Summary: | The PIs propose to develop a new, high-resolution (annual to subdecadal) paleoclimate record (0 to ~2,000 y) from sediment cores taken in Arctic lagoonal settings adjacent to rivers emptying into the Beaufort Sea. This effort is a follow-up to an EAGER award that allowed collection of initial core material and a seismic dataset in Simpson Lagoon near the Colville River delta in August 2010. Initial results suggest that these sediment cores contain a valuable history of system response to climate change on the adjacent continent (e.g., river drainage basins) and terrestrial-marine linkages. All cores will be analyzed for stratigraphy (X-radiography), bulk organic and mineral content, granulometry, and geochronology (239,240Pu/137Cs). Detailed analysis for paleoclimate proxies will be carried out: the age-depth relationship for the deeper part of these cores will be determined using radiocarbon. Climate indicators that will be applied are organic biomarkers (lignin-phenols, cutins, plant pigments, and รค13C) and mineral tracers (major and trace element chemistry, stable isotopes, clay mineralogy, heavy mineral assemblages, granulometry, event-layer stratigraphy). The central hypothesis is that lagoonal settings within the Beaufort Sea contain high quality sediment records because they receive sediment input from larger rivers that drain the Brooks Range, that, if exploited, will dramatically improve our knowledge of high Arctic paleoclimate over the last two millenia. The PIs hypothesize three distinct sources: 1) rivers that drain the Brooks Range and the Arctic Coastal Plain (ACP), 2) storms that erode shoreline permafrosted ACP deposits and overwash barrier islands, 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 will examine the downcore record of temporal variations in layers, contrasting sites to decouple spatial changes in sources. Since the three source end-members have distinct mineral/POC composition, they believe that temporal variations will provide proxy information about climate changes that influence their flux magnitude including 1) landfast ice extent, 2) river sediment supply from the glaciated uplands, 3) permafrost thawing, 4) summer-fall storminess, and 5) coastal primary productivity. Noting the rapid changes that have occurred in the Arctic during the latter half of the 20th century, the federal interagency Study of Environmental Arctic Change (SEARCH) program has cited the need to determine to what extent recent and ongoing climate changes in the Arctic can be attributed to anthropogenic forcing. A successful project will contribute to answering that question.
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