Dr. Branwen Williams Claremont McKenna Colleges
Long-lived encrusting coralline algae yield robust reconstructions of environmental change at the mid-to-high latitudes from their annually-banded high-magnesium calcite skeleton. The magnesium to calcium ratio measured in their skeleton reflects ambient seawater temperature at the time of formation. Thus, reconstructions from these algae are important to understanding the role of natural modes of climate variability versus that of external carbon dioxide in controlling climate in data sparse regions such as the northern North Pacific Ocean/southern Bering Sea. Here, we reconstruct regional seawater temperature from the skeletons of nine algae specimens from two islands in the Aleutian Archipelago. We find that seawater temperature increased ~1.4°C degrees over the past 350 years. The seawater reconstruction correlates with storminess because storms moving across the North Pacific Ocean bring warmer water to the archipelago. However, this connection is not robust prior to the 20th century. This indicates that North Pacific climate processes inferred from the instrumental records should be cautiously extrapolated when describing earlier non-analogous climates or future climate change.