Mineral Weathering in the Arctic


Arctic Research Initiative
2007 Funded Project

Project Summary

The ultimate “geologic” sink of atmospheric CO2 is calcium-magnesium carbonates in marine sediments. The calcium and magnesium ions are supplied by weathering of silicate minerals on the continents. Silicate weathering and transport of dissolved calcium and magnesium ions to the ocean are thus of paramount importance for the long-term stability of Earth’s climate. On shorter time scales (<105 yr) weathering of carbonate mineral also consumes atmospheric/soil CO2 and has to be included in models of the carbon cycle.Globally, mineral weathering consumes ~0.3 Gt C per year, a flux that is only slightly smaller than the riverine flux of organic carbon. Mineral weathering reactions are temperature- and runoff-dependent, and both factors are thought to increase with increasing atmospheric CO2 concentrations. Weathering rates should therefore increase over the next 50-100 years during which atmospheric CO2 concentrations may more than double. Despite these temperature dependencies, estimates of silicate weathering rates in Arctic river basins indicate that they are comparable to many tropical river basins. However, it is important to realize that these estimates are based on sampling of rivers during Arctic summer, after the peak flow that accompanies ice break-up in early spring. These estimates may therefore be severely biased in yet unknown ways.

We propose to investigate inorganic tracers of mineral weathering in several Arctic rivers in Canada and Russia, with specific focus on the spring flood period. This logistically difficult project is being conducted in collaboration with colleagues at the Woods Hole Research Center (WHRC) and our organic chemistry colleagues, whose proposal to work on the organic aspects of ArcticRiver chemistry was funded by WHOI’s Arctic Initiative in the spring. This collaborative work will provide unprecedented insights into the most important river flow period characteristic of Arctic rivers in general.

Arctic rivers are responding to environmental change. This includes receding permafrost that modifies water movement through Arctic soils. Such changes not only mobilize soil carbon, but also increase the surface area of minerals that are in contact with soil moisture. As Arctic rivers are important sources of freshwater as well as organic and inorganic nutrients to the Arctic Ocean, hydrochemical investigations of large Arctic rivers are important to understanding the impact of global change on the Arctic in general. We consider this project a baseline study against which future studies of Arctic rivers conducted at higher atmospheric CO2 concentrations can be compared.