Ocean Biogeochemistry; Ocean Carbon cycle; open-coastal ocean exchange; Eastern Boundary Upwelling Systems
Lovecchio Elisa, Gruber Nicolas, Münnich Matthias, Lachkar Zouhair (2017), On the long-range offshore transport of organic carbon from the Canary Upwelling System to the open North Atlantic, in BIOGEOSCIENCES
, 14(13), 3337-3369.
Frischknecht Martin, Muennich Matthias, Gruber Nicolas (2017), Local atmospheric forcing driving an unexpected California Current System response during the 2015-2016 El Nino, in GEOPHYSICAL RESEARCH LETTERS
, 44(1), 304-311.
Nagai Takeyoshi, Gruber Nicolas, Frenzel Hartmut, Lachkar Zouhair, McWilliams James C., Plattner Gian-Kasper (2015), Dominant role of eddies and filaments in the offshore transport of carbon and nutrients in the California Current System, in JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
, 120(8), 5318-5341.
Frischknecht M., Muennich M., Gruber N. (2015), Remote versus local influence of ENSO on the California Current System, in JOURNAL OF GEOPHYSICAL RESEARCH-OCEANS
, 120(2), 1353-1374.
The coastal ocean and especially the eastern boundary upwelling systems (EBUS) represent a major uncertainty for quantifying the global carbon cycle. Although EBUS cover only about one percent of the global ocean surface area, they represent global hotspots of biogeochemical transformations, with very high rates of primary production, leading to about 10% of global export production. Despite decades of research, their role for the global-scale cycling of carbon and nutrient elements is not well known. Key reasons for the slow rate of progress are the complex physical and biogeochemical dynamics, insufficient data relative to the high degree of variability and the difficulties associated with the development of adequate modeling tools. Especially ill understood, is the interaction of the coastal ocean with the adjacent open ocean basins. This comprises on the one hand of the transport of inorganic carbon and nutrients from the open ocean toward the coast as part of the closure of the global biogeochemical loop, and on the other hand, the transport of largely organic carbon and nutrients from the coast to the open ocean, where it can fuel net heterotrophy and cause net outgassing of CO2. Such processes are not represented at all in the current generation of global Earth System Models, largely due to resolution constraints that prevent these models from simulating the coastal dynamics. Here we propose to investigate the exchange of carbon and nutrients between the EBUS and the open ocean and the net role of the EBUS on the large-scale cycling of carbon and nutrients by using two newly developed setups of the Regional Oceanic Modeling System (ROMS) - one for the Canary Current System and the Atlantic Ocean Basin, and one for the California Current System and the Pacific Ocean Basin. These setups permit us to overcome the traditional limitation associated with either regional or global/basin-scale models, as they have the required eddy-resolving resolution in the nearshore regions of the EBUS and the whole basin coverage needed to investigate the open coastal-ocean exchange processes. Using these models as well as the available observations , we will investigate the following key hypotheses: i) The coastal ocean, and especially EBUS represents an integral part of the global closure of the nutrient and carbon cycle due to intense shelf open ocean exchanges; ii) the nutrients and carbon exported laterally from the EBUS represent a substantial part of the open ocean nutrient and carbon budgets, especially in the subtropical gyres where they fuel respiration and productivity; iii) shelf-extent and eddy activity in the EBUS control the extent to which nutrients and carbon returning from the thermocline/deep ocean are retained in the nearshore region or exported to the open ocean;. By comparing the results from the two EBUS and their adjacent ocean basins, we can optimally test and evaluate these hypotheses, as these two systems differ substantially with regard to their topography, mean state, and sensitivity to perturbations. The assessment of these hypotheses will permit us to make substantial progress toward our long-term goal, i.e., the development of a parameterization of coastal ocean biogeochemical processes for global Earth System Models.