Overview

The Arctic is a key region in the Earth System. The Arctic is extremely sensitive to climate change and it has strong feedbacks to global climate. One of the most important feedbacks involves the hydrologic cycle. General Circulation Models predict increased moisture transport to high latitudes and melting of ice stores with continued global warming. Should this occur, the resulting freshening of waters exported from the Arctic Ocean may significantly impact North Atlantic Deep Water (NADW) formation. This in turn has major consequences for global ocean circulation and climate. Already large-scale changes in the arctic hydrologic cycle are evident, including increasing discharge in major Eurasian arctic rivers (Fig. 1).

Fig. 1. Combined discharge of the six largest Eurasian arctic rivers (Yenisey, Lena, Ob', Kolyma, Pechora, Severnaya Dvina). Over the period of record (1936-1999), combined discharge has increased 7% (128 km3/y). (from Peterson et al. 2002. Science) (open pdf).

The PARTNERS project is a 5-year project (2002-2007), funded by the US National Science Foundation's Arctic System Science Program. The overall objective of the PARTNERS Project is to use river water chemistry as a means to study the origins and fates of continental runoff. Understanding sources and fates of river discharge is important because rivers make an enormous contribution to the freshwater budget of the Arctic Ocean. Selected parameters focusing on tracers of river water are being measured in the six largest rivers that drain the watershed of the Arctic Ocean: the Yenisey, Lena, Ob', Mackenzie, Yukon, and Kolyma rivers (Fig. 2). A wide variety of constituents are being measured, including oxygen isotopes, barium, alkalinity, organic matter, and nutrients. These tracers will provide a means to distinguish contributions from different rivers regionally. They will also provide clues about the functioning of their watersheds. Sampling will be conducted during the high flow season in 2003 and 2006 and during all seasons in 2004 and 2005. Samples are collected near the mouths of the rivers (but above tidal influence) in order to get fully integrated watershed signals and the most relevant freshwater endmember values for oceanographic tracking. The PARTNERS Project will also generate a pan-arctic database on river biogeochemistry for comparison with past and future data in trend analyses. In addition to the scientific aspects of the study, a significant effort is being directed toward Education and Outreach.

Fig. 2. Watersheds of the six largest arctic rivers, all of which are being investigated by the PARTNERS project. Together, these rivers contribute more than 50% of the riverine freshwater entering the Arctic Ocean and their watersheds cover 60% of the Pan-Arctic watershed.