Nevison, Cynthia (Cindy): University of Colorado/INSTAAR (Project Lead)
Project Funding:
2016 - 2020
NRA: 2015 NASA: Ocean Biology and Biogeochemistry
Funded by NASA
Abstract:
The ability to constrain and detect changes in oceanic export flux (EF) is critical to accurately predicting the impact of ocean biota on atmospheric CO2. In past work, which has focused on the Southern Ocean, we have shown that remotely sensed ocean color and atmospheric potential oxygen (APO) data are valuable and complementary metrics for evaluating the ocean carbon cycle. Ocean color products provide high-resolution, near-simultaneous spatial coverage, but satellite-based EF is a higher order product derived from Chl data with relatively high uncertainty. APO data provide a broad-scale, regionally-integrated constraint on the absolute magnitude of EF and further provide information about subsurface ventilation processes that are not captured by ocean color measurements. Our ongoing analysis has revealed that some of the most significant trends in both ocean color and APO data are occurring in the North Pacific, with qualitatively consistent changes observed in both of these wholly independent but complementary datasets. In this proposal, we will explore the North Pacific APO and ocean color trends in the context of our ongoing work to use APO data to constrain satellite EF products. In addition, using datasets developed during our study of the Southern Ocean, we will synthesize satellite-based EF and APO data as complementary metrics for evaluating CMIP5 coupled carbon-climate models and develop ECCO2-Darwin and ECCOv4 as process-based modeling tools that inform this synthesis.
Specific tasks include:
1) Develop improved satellite ocean color-based estimates of export flux (EF), with a
special focus on improving estimates of the annual cycle as well as detecting trends in
timing and magnitude. One problem in monitoring the annual cycle is the gap in coverage
in the large bands of ice-free waters between ~50° - 65° latitude in both hemispheres,
which encompass large regions of the North Pacific, North Atlantic and Southern Oceans.
Production likely occurs during the missing data in these regions, which are characterized by high ef-ratios relative to the global ocean, but the pixels are routinely excluded during processing of ocean color data, due to clouds or high solar zenith angles.
2) Use the eddy-resolving ECCO2-Darwin optimization system to improve our
understanding of the relationship between NPP, NCP, EF and surface O2 fluxes.
Techniques for understanding this relationship using ECCO2-Darwin are being
developed for the Southern Ocean under current NASA funding and will be extended in
this new proposal to the North Pacific and North Atlantic.
3) Synthesize ocean color data and in situ measurements of atmospheric potential oxygen (APO) to understand and reconcile trends observed in both datasets over the past 20 years, which indicate significant shifts in the timing and magnitude of ocean productivity in the North Pacific. This step will involve a series of atmospheric transport model simulations forced with air-sea O2 fluxes derived from steps 1 and 2 as well as from the CMIP5 ocean model archive.
The proposed project targets multiple elements of the NASA Ocean Biology and
Biogeochemistry solicitation, including subelements 2.2-2.4, by quantifying of the magnitude, efficiency, and variability of ocean export production. It targets subelement 2.2 in particular, due to its use of complementary APO data at multiple monitoring sites in the North Pacific. It is a logical extension to the North Pacific and North Atlantic of model and analysis tools developed for the Southern Ocean under current NASA funding (NNX14AL80G).
Publications:
Kahru, M., Lee, Z., Mitchell, B. G. 2017. Contemporaneous disequilibrium of bio-optical properties in the Southern Ocean. Geophysical Research Letters. 44(6), 2835-2842. DOI: 10.1002/2016GL072453
More details may be found in the following project profile(s):
