Subpolar CDOM: Insights from the NAAMES and EXPORTS campaigns in the North Atlantic and North Pacific

Global remote sensing imagery of chromophoric dissolved organic material (CDOM) absorption coefficient reveals a strong interhemispheric difference in CDOM abundance at high latitudes. We carried out intensive CDOM sampling on the NAAMES and EXPORTS campaigns near 50°N in the Atlantic and Pacific Oceans to study the contribution of biological (secondary production) and physical (freshwater input, mixing and solar bleaching) processes controlling CDOM abundance and quality in subpolar waters, that can be contrasted with our previous work in subtropical and Southern Ocean basins. We characterized CDOM using fluorescence excitation-emission (EEM) spectroscopy as well as long pathlength liquid waveguide absorption spectroscsopy. Previous research has suggested that higher abundance of CDOM near 50°N in the Atlantic and Pacific basins has been attributed to terrestrial input, and lower CDOM at a similar latitude in most sectors of the Southern Ocean has been hypothesized to be a result of iron limitation of productivity. Our current results should provide a test of these hypotheses, given the sampling matrix includes iron limitation (North Pacific and Southern Ocean), low terrestrial input (Southern Ocean, subtropics), and medium to high terrestrial input (North Atlantic and North Pacific). Our results will also be discussed in the context of what information on CDOM quality can be retrieved from future ocean color sensors.