HIGH-RESOLUTION MG/CA RECORD OF A BERING SEA CORALLINE RED ALGA SHOWS TELECONNECTIONS WITH ATLANTIC MULTIDECADAL OSCILLATION

We present here a continuous high-resolution record of Mg/Ca variations within an encrusting coralline red alga of the species Clathromorphum nereostratum from the Aleutian Islands, Alaska. Mg/Ca ratios of individual growth increments were analyzed by measuring a single point electron microprobe transect yielding a resolution of 15 samples/year on average, generating a continuous record from 1830 to 1967 of algal Mg/Ca variations. Results show that Mg/Ca ratios in the high-Mg calcite skeleton display pronounced annual cyclicity and archive late spring to late fall sea surface temperature (SST) corresponding to the main season of algal growth. The record displays teleconnections with the signature of the Pacific Decadal Oscillation in the northeast Pacific. A multi-taper power spectrum indicates significant periodicities centered at 60 years. Furthermore, an interbasin comparison with the Atlantic Ocean reveals significant correlations with a tree-ring based reconstruction of the Atlantic Multidecadal Oscillation (AMO – r=0.61, 11 year mean, 1835-1962). The AMO is the leading mode of natural variability in North Atlantic SST and is characterized by 50-70 year oscillations. While recent modeling work has focused on examining the relationship between North Pacific climate variability and the AMO, these efforts have been limited due to the short reliable instrumental record and a lack of marine proxy reconstructions. In fact, in the Bering Sea instrumental SST records are sparse prior to the 1950s. The coralline red algal time series presented here is therefore the first multicentury marine proxy record to highlight the relationships between Bering Sea/North Pacific and North Atlantic climate.