Mercury in the North Atlantic - results of the 2014 GEOTRACES GEOVIDE cruise

Abstract:

We will present results of the recent French-led GEOTRACES GEOVIDE cruise in the North Atlantic Ocean. Research vessel “Pourquoi Pas?” sailed on 15 May from Lisbon, Portugal to Greenland to arrive in Newfoundland, Canada on 30 June 2014. The North Atlantic Current carries the warm subtropical waters northward. They are progressively cooled and eventually reach the formation regions of the North Atlantic Deep Waters in the Labrador and Greenland Seas. This water mass movement drives the Meridional Ocean Circulation and Earth climate. Ongoing climate change makes this a zone of particular interest. Previous OVIDE cruises along the same transect gathered valuable data to investigate temporal changes. This zone also receives atmospheric deposition from Europe and North America where industrial Hg emissions peaked in the 1970s. Here we investigate how climate may impact mercury’s marine biogeochemical cycle, how anthropogenic mercury makes its way into the ocean interior and whether the temporal evolution of mercury emissions is traceable in water masses of different ages. Total mercury was sampled using an ultra-trace clean rosette and determined on board in a class100 clean container following the US EPA 1631 method. Along the >4500km-transect we established full-depth total mercury profiles on 31 stations totaling 530 data points. Average total mercury concentrations were 0.58±0.20pM and showed a general decreasing trend westwards and increased with depth.