Marine Records of Paleoclimate and Paleoenvironments Vs Anthropological Archives in Arctic-Subarctic Regions: Missing Links
Monday, 15 December 2014: 2:25 PM
Climatic changes are recorded by biogenic remains fossilized in marine sediment. These remains and their chemical and isotopic properties allow the establishment of times series of ocean/climate parameters (temperature, sea ice cover, salinity, productivity), as well as of inland vegetation (from pollen grains in continental margin sediments). Such "paleoclimate" studies provide a comprehensive picture of Holocene climate changes at low to mid latitudes but Arctic-subarctic regions remain poorly documented. The rarity of representative records is mostly due to their remote and difficult access, as well as to the generally low biogenic content of marine sediment because of low productivity and/or poor preservation of biominerals (carbonates and opal). Moreover, when available, time series from Arctic-subarctic often suffer poor time resolution and chronological control. Nevertheless, a few paleoclimate records are available. Some of the best-resolved time series are from the Canadian Arctic (eastern and northern Baffin bay, Hudson Strait). They show large amplitude changes during the glacial/interglacial transition in relation with meltwater discharge rates and sea-level changes, and point to the inception of full “postglacial conditions” some 7000 years ago only. Since then, they also recorded millennial type oscillations of smaller amplitude, but out of phase in the western vs eastern subpolar North Atlantic. Paleoclimate reconstructions from marine cores often provide a picture of a "mean" decadal to centennial state of the environment because of the time span represented by sediment samples adding to smoothing effect of sea-floor sediment mixing by benthic organisms. In contradistinction, humane occupation and mobility might be more directly influenced by climate instabilities and extreme events, whose documentation from sedimentary archives represents a real challenge for the geoscience community.