Hydrogen supersaturations in the North and South Atlantic - a possible indicator of nitrogen fixation.

Abstract

It has been demonstrated that nitrogen fixation is a source of hydrogen (H2) to the ocean and therefore measurements of H2 concentrations may be used as a possible indicator of nitrogen fixation (Moore, Punshon, Mahaffey, & Karl, 2009). However, the limited number and sparse distribution of measurements of dissolved hydrogen and nitrogen fixation rates made in the open ocean in the past have made it difficult to quantify the relationship between them. Toward this end, a new method of equilibrating seawater samples for H2 measurement was employed along the 13,000 km Atlantic Meridional Transect (AMT20) from UK to Chile, allowing H¬2 to be measured from underway samples every 3.5 minutes and thereby considerably increasing the number and resolution of H2 measurements made in the open ocean.These high-resolution measurements reveal two regions with high H¬2 concentrations, one in the North Atlantic and one in the South Atlantic.