NOAA/WDS Paleoclimatology - Circum-North Atlantic Area Air Temperature Reconstructions Derived from Tree-ring Maximum Latewood Density Data from 760 to 2017 CE

STUDY NOTES: Millennial May–August temperature reconstructions using tree-ring maximum latewood density data for Eastern Canada, Northern and Central Europe.
ABSTRACT SUPPLIED BY ORIGINATOR: Summer cooling is one of the most direct consequences of explosive volcanic eruptions that can affect ecosystems and human societies. Recent studies revealed a multi-year cooling impact on hemispheric and global summer temperatures after tropical eruptions, yet, the volcanic responses appear to vary on regional scales. Here, we revisit volcano-induced summer cooling in Eastern Canada, Northern and Central Europe by applying superposed epoch analysis on CMIP6-PMIP4 simulations and millennial temperature reconstructions based on tree-ring density. We then examine potential causes modulating region-specific volcanic impact. While confirming that, on average, tropical eruptions over the last millennium have induced a longer cooling (> 4 years) than eruptions from extratropical Northern Hemisphere in all three North Atlantic regions, we show that the peak magnitude of cooling is stronger in Eastern Canada. We also find that the detected volcanic temperature anomalies can be strongly affected by the selection and number of volcanic events and non-volcanic signals embedded in the climate time series. This study highlights the risks of using highly noisy proxy records to investigate volcanic impacts, especially in regions with strong unforced climate variability. The CMIP6-PMIP4 simulations generally agree with the three reconstructions on the average response to tropical eruptions, but their performance is poorer regarding the production of significant cooling after extratropical eruptions. Our results further suggest that the particular sensitivity to tropical eruptions in Eastern Canada is likely related to increased sea ice surrounding Quebec-Labrador associated with the positive Arctic Oscillation and North Atlantic Oscillation formed during the first post-eruption winter.