Open AccessCarbon cycling and burial in New Zealand's fjords
Author(s) -
Hinojosa Jessica L.,
Moy Christopher M.,
Stirling Claudine H.,
Wilson Gary S.,
Eglinton Timothy I.
Publication year - 2014
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1002/2014gc005433
Subject(s) - fjord , carbon cycle , total organic carbon , oceanography , geology , continental margin , carbon fibers , sediment , biogeochemical cycle , earth science , environmental science , geomorphology , paleontology , environmental chemistry , ecosystem , ecology , chemistry , materials science , composite number , composite material , biology , tectonics
Understanding carbon cycling in continental margin settings is critical for constraining the global carbon cycle. Here we apply a multiproxy geochemical approach to evaluate regional carbon cycle dynamics in six New Zealand fjords. Using carbon and nitrogen concentrations and isotopes, lipid biomarkers, and redox‐sensitive element concentrations, we show that the New Zealand fjords have carbon‐rich surface sediments in basins that promote long‐term storage (i.e., semirestricted basins with sediment accumulation rates of up to 4 mm yr −1 ). Using δ 13 C distributions to develop a mixing model, we find that organic carbon in fjord sediments is well‐mixed from marine and terrestrial sources in down‐fjord gradients. This is driven by high regional precipitation rates of >6 m yr −1 , which promote carbon accumulation in fjord basins through terrestrial runoff. In addition, we have identified at least two euxinic subbasins, based on uranium, molybdenum, iron, and cadmium enrichment, that contain >7% organic carbon. Because the strength and position of the Southern Hemisphere westerly winds control precipitation and fjord circulation, carbon delivery and storage in the region are intimately linked to westerly wind variability. We estimate that the fjord region (759 km 2 ) may be exporting up to 1.4 × 10 7 kgC yr −1 , outpacing other types of continental margins in rates of carbon burial by up to 3 orders of magnitude.