Project Funding: 2009 - 2012

NRA: 2006 NASA: Ocean Biology and Biogeochemistry   

Funded by NASA

Abstract:
The Southern Ocean (which is 10% of the Earth's total ocean area) is estimated to be responsible for up to 20% of the global ocean CO2 uptake of 2.2 Pg C yr-1 (Takahashi et al. 2002; Takahashi et al, in prep). However, a roughly two-fold uncertainty exists in the estimated CO2 uptake, and the uncertainty depends largely on whether polar continental shelves covered by seasonal sea ice act as one-way CO2 pumps: in winter out-gassing of CO2-rich water is prevented by the overlying sea ice cover, while in spring-summer rapid onsets of phytoplankton blooms at the ice-edge provide a CO2 sink. The extent to which phytoplankton blooms will provide a CO2 sink is uniquely dependent on downward carbon export, i.e., the biological pump. To improve current assessments and future predictions of carbon fluxes in Southern Ocean sea ice zones, we will investigate the highly seasonally (and interannually) varying dynamic relationships between sea ice, ocean and the ecosystem using 15 years of data from the western Antarctic Peninsula (wAP) region. We are focused on the wAP region for two reasons: (1) it has been shown to be warming faster in winter than anywhere else on earth and (2) remote and in situ physical, biogeochemical and ecosystem data in this region are more extensive than anywhere else in the Antarctic/Southern Ocean region. Our approach will involve building a predictive ice-ocean-ecosystem model through careful data synthesis and model testing over contemporary periods (the last 15-28 years). The predictive model seeks to test the hypothesis that the rectification of air-sea gas exchange has and will continue to decrease due to the combination of reductions in sea ice concentration and grazer populations capable of transporting carbon to the deep ocean. The ecosystem component in the model was designed for global predictions and will allow us to easily incorporate our improvements into global-scale modeling efforts. Two ecosystem processes that we will include in our investigation that have not been well-parameterized or studied in previous ecosystem data synthesis and modeling efforts include (1) the role of sea ice biota in enhancing spring phytoplankton concentrations and CO2 draw down during sea ice melt, and (2) the role of macrozooplankton grazing in influencing phytoplankton community composition and export production. This study will provide the following deliverables: (1) a synthesis of more than 15 years of remote and in situ physical, geochemical and ecosystem data collected from the wAP area, and (2) an improved predictive model for ice-ocean-ecosystem interactions, which can be scaled up to the global level for comparison to other NASA estimates of global climate change. These deliverables are a direct response to the goals of the NASA ROSES Southern Ocean Carbon Program (Data Synthesis, Assimilation and Modeling) to improve future predictions of carbon fluxes in response to climate change. In particular, this study addresses strategic goal 3A by looking at earth from space to advance scientific understanding and meet societal needs, by contributing to the understanding of the role of oceans, atmosphere and ice in the climate system, the predictive capability of its future evolution, the quantification of marine productivity, and the improvement of carbon cycle and ecosystem models.

More details may be found in the following project profile(s):

• NASA Ocean Biology & Biogeochemistry (OBB) Project Profile