The eruption of the Alaskan Aniakchak volcano of 3.6 thousand years ago was one of the largest Holocene eruptions worldwide. The resulting ash is found in several Alaskan sites and as far as Newfoundland and Greenland. In this study, we found ash from the Aniakchak eruption in a marine sediment core from the western Chukchi Sea in the Arctic Ocean. Combined with radiocarbon dates on mollusks, the volcanic age marker is used to calculate the marine radiocarbon reservoir age at that time.

This study focuses on understanding climatic and oceanographic variations that took place during the last 1000 years. We studied sediment samples from the Labrador Sea, looking for evidence of events of freshwater and iceberg discharges to this region. The importance of this study is to evaluate when these events happened and their consequences. The freshening of the Labrador Sea region may have played a major role in promoting cooling during the 15th to 19th centuries.

We reconstruct changes in the warm water transport from the subtropical to the subpolar North Atlantic over the last 10 000 years. We use stable isotope and Mg / Ca ratios measured on surface and subsurface dwelling foraminifera. Results indicate an overall stable warm water transport at surface. The northward transport at subsurface evolves stepwise and stabilizes at 7 ka BP on the modern mode. These ocean transport changes seem to be controlled by the meltwater inflow into the North Atlantic.

Our new planktonic foraminiferal stable carbon isotopic data from the western South Atlantic show major decreases during abrupt climate change events of the last glacial. These anomalies are likely related to periods of a sluggish Atlantic meridional overturning circulation and increase (decrease) in atmospheric CO₂ (stable carbon isotopic ratios). We hypothesize that strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump are responsible for these decreases.

Data assimilation has been successfully applied in the field of paleoclimatology to reconstruct past climate. However, data reconstructed from proxies have been assimilated, as opposed to the actual proxy values, which prevented full utilization of the information recorded in the proxies. This study propose a new data assimilation system in which actual proxy data are directly assimilated.

Wildfires impact ecosystems, climate, and atmospheric chemistry. Records that predate instrumental records and industrialization are needed to study the climatic controls on biomass burning. In this study, we analyzed organic chemicals produced from burning of plant matter that were preserved in an ice core from the Eurasian Arctic. These chemicals are elevated during three periods that have similar timing to climate variability. This is the first millennial-scale record of these chemicals.

Using a unique annually-laminated record (varve) from the western Canadian High Arctic, we found a significant relationship between our varve record and instrumental and reconstructed Pacific Decadal Oscillations (PDOs). The negative (positive) PDO (North Pacific Index) phases increase precipitation as low sea-ice extent, warmer temperature and winds reach our region more efficiently. Our results imply that future negative PDO phases will likely impact the already rapidly warming Arctic.