Stammerjohn, Sharon: University of Colorado at Boulder (Project Lead)
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):