Description: Since the 1970s tremendous changes have been observed in the Arctic region. As such, the surface air temperature within this region has increased twice the global average and according to existing climate model predictions, this trend will continue in the future (IPCC, 2007). However, interpretation of such transformation, which results from greenhouse warming, is still difficult. This is due to a lack of knowledge about the influence of multi-annual to decadal climate variations and the fact that climatic data from this region are usually temporally and spatially biased. Therefore, a better understanding and further research on the effects and predictability of climate variability is needed. We examined the growth variability in shells of the bivalve mollusc Arctica islandica L. which is affected by environmental factors, mainly temperature and food supply. The prime objective of the project was to compare the shell growth of molluscs from two distinct populations in European Arctic and to determine the external factors influenced on the annual shell growth variability in A. islandica. We compared shells from two sampling sites: the northern Norwegian coast and the Kola Peninsula coast (SW Barents Sea). Both localities are in the realm of the Norwegian Coastal Current (after crossing the border to Russia it is called the Murman Coastal Current). For the investigation of the annual and inter-annual growth variability all collected shells were cut, 3 mm thick-sections were attached to a glass slide, grinded, polished and stained. Annual growth bands were identified and measured. Samples for the stable isotope (δ18O, δ13C) analysis and the seasonality approach were taken using a hand drill and the milling technique. Based on increments measurements of 62 specimens, we found significant difference in growth rates between these two locations, which presumably resulted from a difference in thermal regime in the two sites and in the depth of collection of the molluscs. By comparison of growth chronologies with the time series of environmental and climatic parameters, we indicated a growth response of a specimen from the Norwegian coast to seawater temperature variability in the study area and found a similarity in a pattern with NAO-index. The molluscs from the Barents Sea responded to variation in air temperature, especially during colder periods. Analyzed stable isotope ratio (δ18O, δ13C) profiles showed cyclic patterns within annual growth lines related to seasonal changes in temperature and primary production. The obtained values of stable oxygen isotope ratio allowed a reconstruction of seasonal changes of water temperature, but for the precise results accurate data on salinity or δ18O ratio of seawater is needed.

Description: Since the 1970s tremendous changes have been observed in the Arctic region. As such, the surface air temperature within this region has increased twice the global average and according to existing climate model predictions, this trend will continue in the future (IPCC, 2007). However, interpretation of such transformation, which results from greenhouse warming, is still difficult. This is due to a lack of knowledge about the influence of multi-annual to decadal climate variations and the fact that climatic data from this region are usually temporally and spatially biased. Therefore, a better understanding and further research on the effects and predictability of climate variability is needed. We examined the growth variability in shells of the bivalve Arctica islandica which is affected by environmental factors, mainly temperature or food supply. We compare shells from two sampling sites, the northern Norwegian coast and Kola Peninsula coast (SW Barents Sea). Both localities are in the realm of the Norwegian Coastal Current (after crossing the border to Russia it is called the Murman Coastal Current). For the investigation of the annual and inter-annual growth variability all collected shells were cut parallel to the line of strongest growth (LSG) and 3 mm thick-sections were attached to a glass slide. After grinding and polishing, the cross-sections were stained in Mutvei´s solution. Annual growth bands were identified and measured. Samples for the stable oxygen isotope (δ18O) analysis and the seasonality approach were taken using a hand drill and the milling technique. As our prime objective we compared the shell growth of the Norwegian and the Russian populations and determined the external factors controlling the annual shell growth variability in A. islandica. Furthermore, the shells from both populations have been checked for decadal oscillations (NAO? ACRI?). Finally, stable oxygen isotope ratio (δ18O) profiles have been measured to identify seasonal signals and to reconstruct regional water temperature variability at a sub-annual level.

Description: Understanding the climate of the past is essential for anticipating future climate change. Palaeoclimatic archives are the key to the past, but few marine archives (including tropical corals) combine long recording times (decades to centuries) with high temporal resolution (decadal to intra-annual). In temperate and polar regions carbonate shells can perform the equivalent function as a proxy archive as corals do in the tropics. The bivalve Arctica islandica is a particularly unique bio-archive owing to its wide distribution throughout the North Atlantic and its extreme longevity (up to 500 years). This paper exemplifies how information at intra-annual and decadal scales is derived from A. islandica shells and combined into a detailed picture of past conditions. Oxygen isotope analysis (δ18O) provides information on the intra-annual temperature cycle while frequency analysis of shell growth records identifies decadal variability such as a distinct 5-year signal, which might be linked to the North Atlantic Oscillation.

Description: Since the 1970s tremendous changes have been observed in the Arctic region. As such, the surface air temperature within this region has increased twice the global average and according to existing climate model predictions, this trend will continue in the future (IPCC, 2007). However, interpretation of such transformation, which results from greenhouse warming, is still difficult. This is due to a lack of knowledge about the influence of multi-annual to decadal climate variations and the fact that climatic data from this region are usually temporally and spatially biased. Therefore, a better understanding and further research on the effects and predictability of climate variability is needed. We examined the growth variability in shells of the bivalve mollusc Arctica islandica L. which is affected by environmental factors, mainly temperature and food supply. The prime objective of the project was to compare the shell growth of molluscs from two distinct populations in European Arctic and to determine the external factors influenced on the annual shell growth variability in A. islandica. We compared shells from two sampling sites: the northern Norwegian coast and the Kola Peninsula coast (SW Barents Sea). Both localities are in the realm of the Norwegian Coastal Current (after crossing the border to Russia it is called the Murman Coastal Current). For the investigation of the annual and inter-annual growth variability all collected shells were cut, 3 mm thick-sections were attached to a glass slide, grinded, polished and stained. Annual growth bands were identified and measured. Samples for the stable isotope (δ18O, δ13C) analysis and the seasonality approach were taken using a hand drill and the milling technique. Based on increments measurements of 62 specimens, we found significant difference in growth rates between these two locations, which presumably resulted from a difference in thermal regime in the two sites and in the depth of collection of the molluscs. By comparison of growth chronologies with the time series of environmental and climatic parameters, we indicated a growth response of a specimen from the Norwegian coast to seawater temperature variability in the study area and found a similarity in a pattern with NAO-index. The molluscs from the Barents Sea responded to variation in air temperature, especially during colder periods. 6 Analyzed stable isotope ratio (δ18O, δ13C) profiles showed cyclic patterns within annual growth lines related to seasonal changes in temperature and primary production. The obtained values of stable oxygen isotope ratio allowed a reconstruction of seasonal changes of water temperature, but for the precise results accurate data on salinity or δ18O ratio of seawater is needed.