Reconstructing past environmental conditions in the Arctic using shell growth records from Svalbard, Norway
Global environmental conditions are changing at a rapid rate. A lack of long-term instrumental records with which to quantify the rate and magnitude of change, particularly in the Arctic region, provides significant challenges to detection and attribution efforts. One way to determine past conditions is using geological proxy archives. Once properly calibrated and verified, these archives can be used to hindcast particular environmental conditions. Similar to other bivalve species, Hiatella arctica is a potential environmental proxy due to its apparent sensitivity to ambient ocean conditions and the prominent annual growth bands in its shell. These annual bands allow the construction of an absolutely-dated growth chronology that can serve as a template for geochemical sampling. A species-specific preparation method was developed to create a readable cross-section of the shell. Using digital imaging software coupled with a microscope, growth bands are counted and measured to determine shell age. As in dendrochronology, annual increments from multiple clams are visually compared and cross-dated. Statistical analyses for the strength of the “common signal” are then run on the increment measurements to verify the robustness of the constructed chronology. Once accepted, the chronology can be compared to other environmental records to determine potential forcing mechanisms. Initial results suggest that shell growth in H. arctica from Svalbard, Norway is synchronous and likely driven from a common environmental forcing. Due to its ubiquitous presence throughout the Arctic, a species-specific calibration of H. arctica would enable study comparisons across environmentally-diverse regions.