4 resultados para Nordic Area
em Publishing Network for Geoscientific
Resumo:
This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007-2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0°C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and rising permafrost temperatures.
Resumo:
High-resolution records of coarse lithic content and oxygen isotope have been obtained in a piston core from the Irminger Basin. The last glacial period is characterized by numerous periods of increased iceberg discharges originating partly from Iceland and corresponding to millennial-scale instabilities of the coastal ice sheets and ice shelves in the Nordic area. A comparison with midlatitude sediment cores shows that ice-rafted material corresponding to the Heinrich events was deposited synchronously from 40° to 60°N. There are thus two oscillating systems: every 5-10 kyr massive iceberg armadas are released from large continental ice caps, whereas more frequent instabilities of the coastal ice sheets in the high latitude regions occur every 1.2-3.8 kyr. At the time of the Heinrich events the synchroneity of the response from all the northern hemisphere ice sheets attests the existence of strong interactions between the two systems.
Resumo:
Cold-seep environments and their associated symbiont-bearing mega faunal communities create islands of primary production for macro-and meiofauna in the otherwise monotonous and nutrient-poor deep-sea environment. To examine the spatial variation and distribution patterns of metazoan meiobenthos in different seepage-related habitats, samples were collected in two regions off Norway: several pockmarks associated with the Storegga Slide including the Nyegga pockmark area, and the active, methane-venting Haakon Mosby Mud Volcano west of the Barents Sea during the Vicking cruise aboard the RV ''PourquoiPas?'' in May-June 2006. Meiofaunal samples at control sites were sampled with a multiple corer, while the other sites were sampled with push cores operated by the ROV Victor6000.The meiofaunal samples were fixed in 4% buffered formaldehyde and washed over a 32 mm-mesh sieve. Metazoan meiofauna were extracted by density gradient centrifugation. All material was fixed with 4% buffered formalin and stained with Rose Bengal. The metazoan meiofauna was sorted out, enumerated and identified down to major taxa under the stereomicroscope. Afterwards, abundances of Nematodes were depth integrated over the top 5 cm to gain individual abundances per 10 cm**2.
Resumo:
Alkenone sediment data from the Nordic seas and North Atlantic are compared to those from Sikes et al. (1997) for the Southern Ocean to evaluate further UK37 and UK37' as proxies to estimate cold temperatures (<10°C) and the effect of salinity and temperature in the relative abundance of 37:4 to the total abundance of C37 alkenones (37:4%). UK37 and UK37' are found to be equally viable as proxies, but there are significant regional differences in their cold temperature dependence. The measurement of 37:4% in cores from the North Atlantic region can be used to identify situations when UK37' is not a reliable paleothermometer. Variations in salinity are probably responsible for changes in the sedimentary record of 37:4%, and a preliminary calibration has been obtained for 37:4%=f(salinity). This new relationship should be further confirmed through field or laboratory experiments, but it paves the way to derive a molecular proxy to reconstruct paleosalinity in surface waters.