My work aims to reconstruct and understand past climate change and atmospheric composition, using deep ice cores from Greenland and Antarctica. I combine ice core measurements, numerical modeling and fieldwork to achieve these goals.
I have an enduring interest in abrupt climate change of the last ice age, the so-called Dansgaard-Oeschger cycle. For each D-O event, Greenland warmed by about 10°C within decades. We discovered that during these events the hemispheres communicate via slow (200 year delayed!) oceanic signals, as well as via fast atmospheric signals. Using climate models I have investigated the role of the Southern Ocean in setting the pace of the D-O cycle.
Ongoing work is to reconstruct the timing, magnitude and spatial pattern of climate change over the Greenland ice sheet using nitrogen isotopes, and to understand how this relates to the rate of ice retreat during the last deglaciation.
I have extensively studied the firn layer, which is the 50 to 100 m thick layer of unconsolidated snow on top of ice sheets. I work both on firn densification and on firn air transport.
Ice core timescales (or chronologies) are critical for the correct interpretation of ice core records. I continue to work on improving ice core chronologies through firn densification modeling and volcanic matching. I have contributed to ice core time scales of the NEEM, GISP2, WAIS Divide, South Pole and RICE ice cores.
Other research projects include radiometric Kr-81 dating of ancient ice in Antarctica, in situ radiocarbon production in ice, and the relationship between temperature and accumulation in Antarctica. In a previous life, I worked on quantum dots and spintronics.
