Xiahong Feng - Current Research Interests in Stable Isotope Geochemistry

• Effect of Sea Ice on Arctic Precipitation
• Hydrogen and oxygen isotope studies of tree rings
• Oxygen and hydrogen isotopic compositions in leaf water
• Study of plants’ water used efficiency using C isotopes of tree rings
• Carbon and nitrogen cycles in plant-soil systems
• Isotope hydrology and hydrochemistry

Eric Posmentier at the DOE instrument platform for atmospheric studies in Barrow, AK. August 2008.

Effect of Sea Ice on Arctic Precipitation

It has recently been forecasted that Arctic summer sea ice may completely disappear sometime during this century. Sea ice is an indicator of and has an influence on the rest of the climate system. It has a strong, direct and well-documented effect on Arctic albedo and sea surface temperature, and enhances evaporation and the Arctic hydrologic cycle. The sea ice-evaporation/precipitation link is a fundamental component of climate dynamics, and has been cited as an essential element of global warming, abrupt climate change, Dansgaard-Oeschger events, the Pleistocene ice ages, and “snowball earth”. However, there are remarkably few measurements that quantify the fundamental link between the ice-free Arctic Ocean area and evaporation/precipitation. The objective of this project is to quantify how moisture evaporated from the Arctic Ocean and surrounding seas contributes to precipitation in the Arctic regions, and how such moisture supply is controlled by sea ice extent. We do t his by studying oxygen and hydrogen isotopic compositions in precipitation collected storm-by-storm at two Arctic stations, Barrow and Atqasuk, Alaska. More Arctic stations in Canada, Norway, Greenland, and Russia are under development for similar sampling programs. By looking at weather patterns and its evolution that are responsible to a given storm, we are determining what part of the ocean surface contributes to the moisture budget of the storm using D/H and 18 O/ 16 O ratios in the precipitation samples. The results will be interpreted for the individual influences of the ice-free area of the Arctic, of storm tracks, of atmospheric temperatures at both moisture sources and precipitation sites, and of circulation changes associated with the Arctic Oscillation and/or the North Atlantic Oscillation.

This project will yield a quantitative understanding of the link between sea ice and moisture sources of Arctic precipitation, which is important in the study of climate dynamics on a wide range of time scales. It will also provide new data and insight for interpretations of climate information recorded in ice cores, which is relevant for testing global warming projections, abrupt global change scenarios, and ice age theories, as well as for further verification of climate models.