Westberry, Toby: Oregon State University (Project Lead)
Project Funding:
2008 - 2010
NRA: 2007 NASA: Carbon Cycle Science
Funded by NASA
Abstract:
High-latitude seasonal seas are among the most temporally varying ocean regions, and they play a predominant role in global ocean carbon cycling. However, the seasonal dynamics of these regions can differ dramatically from one basin to the next. For example, seasonal patterns in chlorophyll (Chl) concentrations for the subarctic North Atlantic and North Pacific are markedly different and have a long history of documentation. The N. Pacific exhibits very constant and low Chl throughout the year, while the N. Atlantic exemplifies a productive spring bloom system. A number of hypotheses to explain this discrepancy have been proposed involving both top-down and bottom-up controls. The result has been a framework for relating phytoplankton-grazer coupling to ecosystem biogeochemical function, particularly export production. Understanding the controls on this coupling is critical for quantifying the role of high latitude oceans in carbon cycling and climate change.
Using new satellite information on phytoplankton biomass and physiology, we have discovered something rather unexpected in the N. Atlantic and N. Pacific: the two basins appear to have similar sized spring/summer “blooms” when assessed by satellite-derived phytoplankton carbon biomass (phytoC). If this preliminary finding is verified, it suggests that we need to re-evaluate controls on phytoplankton growth and loss terms, and the resulting regional carbon export. Differences between our new results and historical ones can be traced to the independent behavior of phytoC and Chl. In the N. Pacific, we find that spring/summer increases in phytoC are accompanied by substantial decreases in cellular Chl:C that effectively mask the bloom in terms of Chl. In the N. Atlantic, on the other hand, phytoC and Chl:C increase in parallel, giving rise to the classical spring bloom.
While our revised view of N. Pacific phytoplankton dynamics is intriguing and supported by parallel modeling studies, verification of our results and additional analyses are needed. The objectives of the project proposed here are to (1) collect necessary field measurements to test new satellite products upon which our preliminary analysis is based, (2) conduct a detailed error analysis of the bio-optical models employed to generate the new products, (3) investigate the implications of our findings on hypothesized control mechanisms for the two basins, and (4) assess the impact of our results on carbon export. The field component of this project involves 3 multidisciplinary research cruises during the first two years, with ship time coming at no expense to the project. These studies will also include deployment of new ARGO-like floats equipped with bio-optical sensors to provide multi-year match-up data with satellite products. In addition to supporting the research goals of this project, our field measurement suite will significantly enhance available high latitude data for subsequent studies by the ocean color community.
More details may be found in the following project profile(s):
