Suitability of the Coralline Alga Clathromorphum compactum as an Arctic
Archive for Past Sea ice Cover
Abstract
Arctic sea ice cover has been steeply declining since the onset of
satellite observations in the late 1970s. However, the available
annually resolved sea ice data prior to this time are limited. Here, we
evaluated the suitability of annual trace element (Mg/Ca) ratios and
growth increments from the long-lived annual increment-forming benthic
coralline red alga, Clathromorphum compactum, as high-resolution
sea ice cover c. It has previously been shown that growth and Mg/Ca of
C. compactum are strongly light controlled and therefore greatly
limited during polar night and underneath sea ice cover. We compare
algal data from 11 sites collected throughout the Canadian Arctic,
Greenland and Svalbard, with satellite sea ice data. Our results
suggested that algal growth anomalies most often produced better
correlations to sea ice concentration than Mg/Ca alone or when averaging
growth and Mg/Ca anomalies. High Arctic regions with persistently higher
sea ice concentrations and shorter ice-free seasons showed strongest
correlations between algal growth anomalies and satellite sea ice
concentration over the study period (1979-2015). At sites where ice
breakup took place prior to the return of sufficient solar irradiance,
algal growth was most strongly tied to a combination of solar irradiance
and other factors such as temperature, suspended sediments,
phytoplankton blooms and cloud cover. These data are the only annually
resolved in situ marine proxy data known to date and are of utmost
important to gain a better understanding of the sea ice system and to
project future sea ice conditions.