Wang, Xiujun (Wendy): UMD/ESSIC (Project Lead)
Project Funding:
2008 - 2010
NRA: 2007 NASA: Carbon Cycle Science
Funded by NASA
Abstract:
The tropical oceans play a very important role in the global carbon cycle and climate because they are the dominant natural oceanic source of CO2 to the atmosphere. Global carbon cycle modeling studies indicate that the tropical oceans contribute the largest fraction of the interannual variability of the global ocean-atmosphere CO2 flux. However, there are considerable discrepancies among different approaches (e.g., observations, ocean carbon models and inverse models), and large uncertainties in the estimates of the CO2 fluxes at basin scales. Here, we propose a combined study employing satellite data and validated regional biogeochemical models to address a number of key issues leading to a better understanding of the large-scale temporal and spatial variability of carbon fluxes in the tropical oceans, aiming to reduce major uncertainties in the global carbon cycle. In particular, we seek to answer: what are the impacts of climate induced biogeochemical changes on the carbon fluxes between the upper ocean and deep ocean, and between the tropical oceans and the atmosphere?
The proposed activity builds on our existing NASA funded research “Seasonal to Decadal Variations of the Oceanic pCO2 and Air-Sea Flux of CO2 in the Equatorial Pacific (CARBON/04-0000-0070)”. Our team has a long history of modeling the tropical ocean circulation and dynamics, and more recently the tropical ecosystem and biogeochemistry. In particular, we have developed and tested a basin scale ocean-ecosystem model for all the tropical oceans (i.e., the Indian Ocean, and the tropical Pacific and Atlantic Oceans). We have implemented a carbon chemistry model into the ocean-ecosystem models, tested and validated for the tropical Pacific Ocean. Recently, we have developed a chlorophyll dynamic model that deals with phytoplankton acclimation to changes in irradiance, nutrient concentration and temperature, which has been validated in the tropical Pacific. We will expand this advanced ecosystem-carbon model to the entire tropical oceans to quantify spatial patterns and variability of carbon fluxes between the ocean and atmosphere.
There have been extensive and growing databases of remotely sensed and in situ biogeochemical measurements, including chlorophyll and particulate organic carbon (POC). We will use these data for model validations and improvements. The major objectives of the proposed studies are to determine the size and variability of the CO2 source of the tropical oceans at decadal and longer time scales. We will undertake a series of studies to investigate: (1) impacts of iron-silica interaction and co-limitation on the spatial and temporal variability of the sea surface pCO2, and sea-air CO2 fluxes, (2) the impacts of C:N and C:Chl ratio variability on the tropical oceanic carbon cycle, including primary productivity and export production, (3) how past and present climate variability and change regulate the spatial and temporal variability of the sea surface pCO2, and sea-air CO2 fluxes in each ocean basin, (4) impact of physical-biological feedback on the ocean carbon cycle, and (5) the uncertainties in estimates of the tropical oceanic CO2 source, resulting from different wind products and gas exchange formulations.
More details may be found in the following project profile(s):
