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Title: Seasonal SIMS δ18O record in Astarte borealis from the Baltic Sea tracks a modern regime shift in the NAO
IntroductionAstarte borealisholds great potential as an archive of seasonal paleoclimate, especially due to its long lifespan (several decades to more than a century) and ubiquitous distribution across high northern latitudes. Furthermore, recent work demonstrates that the isotope geochemistry of the aragonite shell is a faithful proxy of environmental conditions. However, the exceedingly slow growth rates ofA. borealisin some locations (<0.2mm/year) make it difficult to achieve seasonal resolution using standard micromilling techniques for conventional stable isotope analysis. Moreover, oxygen isotope (δ18O) records from species inhabiting brackish environments are notoriously difficult to use as paleoclimate archives because of the simultaneous variation in temperature and δ18Owatervalues. MethodsHere we use secondary ion mass spectrometry (SIMS) to microsample anA. borealisspecimen from the southern Baltic Sea, yielding 451 SIMS δ18Oshellvalues at sub-monthly resolution. ResultsSIMS δ18Oshellvalues exhibit a quasi-sinusoidal pattern with 24 local maxima and minima coinciding with 24 annual growth increments between March 1977 and the month before specimen collection in May 2001. DiscussionAge-modeled SIMS δ18Oshellvalues correlate significantly with bothin situtemperature measured from shipborne CTD casts (r2 = 0.52, p<0.001) and sea surface temperature from the ORAS5-SST global reanalysis product for the Baltic Sea region (r2 = 0.42, p<0.001). We observe the strongest correlation between SIMS δ18Oshellvalues and salinity when both datasets are run through a 36-month LOWESS function (r2 = 0.71, p < 0.001). Similarly, we find that LOWESS-smoothed SIMS δ18Oshellvalues exhibit a moderate correlation with the LOWESS-smoothed North Atlantic Oscillation (NAO) Index (r2 = 0.46, p<0.001). Change point analysis supports that SIMS δ18Oshellvalues capture a well-documented regime shift in the NAO circa 1989. We hypothesize that the correlation between the SIMS δ18Oshelltime series and the NAO is enhanced by the latter’s influence on the regional covariance of water temperature and δ18Owatervalues on interannual and longer timescales in the Baltic Sea. These results showcase the potential for SIMS δ18Oshellvalues inA. borealisshells to provide robust paleoclimate information regarding hydroclimate variability from seasonal to decadal timescales.  more » « less
Award ID(s):
2004618
PAR ID:
10515512
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
Frontiers
Date Published:
Journal Name:
Frontiers in Marine Science
Volume:
10
ISSN:
2296-7745
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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