The data set presented here represents growing season (late-1999, 2000 and 2001) values of net carbon dioxide exchange, photosynthesis, and respiration between the atmosphere and wet tundra. The site is located at Alexandra Fiord on the east-central side of Ellesmere Island, Nunavut, Canada at 78.54N 75.55W, 50 m elevation asl. As part of the International Tundra Experiment (ITEX), Greg Henry of the University of British Columbia has been increasing air and soil temperatures at this site since 1993 using small open-topped chambers (OTCs). These OTCs are hexagonal in shape and are constructed of transparent fiberglass. They typically raise air and soil temperatures by 1 to 4C. The data set shows periodic carbon dioxide exchange data from the end of the 1999 growing season and throughout the 2000 and 2001 growing seasons in ambient plots and long-term (7-9 yrs) warmed (OTC) plots. The most complete data set (2001) begins in spring before winter snowmelt and ends at the end of summer when snow has once again covered the ground. The data are from 199908040800 to 200108042400 UTC.