Mid-Holocene Marine Paleoclimate Reconstruction Through Schlerochronological Analysis of Arctica islandica from Finnmark, Rolvsøya, Northern Norway

• Main Author: Mark, Samuel Zimet
• Format: Text
• Language: unknown
• Published: SCARAB 2016
• Subjects: Paleoclimatology; Norway; A. islandica; climate change; Holocene; Atmospheric Sciences; Biogeochemistry; Climate; Geochemistry; Geology; Glaciology; Oceanography; Arctic; Rolvsøya; Arctica islandica; Climate change; Finnmark; North Atlantic; North Atlantic oscillation; Northern Norway
• Online Access: https://scarab.bates.edu/honorstheses/154; https://scarab.bates.edu/cgi/viewcontent.cgi?article=1184&context=honorstheses

The long-lived marine bivalve Arctica islandica records the climatic conditions the organism experienced during its lifetime in its carbonate shell. Both the geochemical composition and the annually banded growth increments respond to ambient environmental forcing and are potentially valuable high resolution paleoclimatic proxies at high-latitude marine locations. Persistent climatological phenomena such as the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) at the climatologically and oceanographically significant island of Rolvsøya from which a series of A. islandica specimens were recovered dictate annual increment width via the oceanographic dynamics such as temperature and productivity. Furthermore, periods of synchronous growth can be identified in specimens that lived contemporaneously, allowing for floating and anchored chronologies to be established. A. islandica also secretes its aragonitic shell material in isotopic equilibrium with the ambient seawater. δ18O is inversely correlated with temperature in seawater; examining concentration of δ18O to δ16O in A. islandica allow for the reconstruction of temperature and seasonality. Growth rate and longevity measurements were made for sixty A. islandica specimens aged between 7315 and 1563 years B.P and geochemical analyses for two mid-Holocene specimens were undertaken. Growth analyses revealed accelerated growth during ontogenesis when compared to late-Holocene specimens. Two modifications of a preexisting δ18O based temperature derivation are presented in an attempt to better reflect conditions during the time period of interest. A decrease in seasonality, from 2.97°C to 1.53°C, occurred between 6245 B.P to 6011 B.P, potentially indicative of decreased vertical water column mixing as a result of increased overall temperature.