Acronym: OCB-046
Program: Ocean Carbon & Biogeochemistry [OCB]
URL: Project Web Site
Start date:
End date:
Geolocation: Equatorial Pacific
Description:

Decadal Changes in the Equatorial Pacific Planktonic Ecosystem Structure and Functioning: Impact of Climate Conditions

from www.us-ocb.org

The equatorial Pacific Ocean plays a very important role in the global carbon cycle and climate in two aspects. Firstly, it is the largest natural oceanic source of CO2 to the atmosphere, and responsible for the interannual variability of the global ocean-atmosphere CO2 fluxes. Secondly, the equatorial Pacific Ocean has the direct linkage to climate variability such as the El Niño/Southern Oscillation (ENSO), and the Pacific Decadal Oscillation (PDO). The efforts to understand the causes and consequences of ENSO have greatly expended in the past few years due to numerous studies of the interannual variability in the equatorial Pacific Ocean circulation, ecosystem and biogeochemical processes. Observational studies have identified two possible regime shifts in physical processes around 1976/77 and 1998/99, due to substantial changes of the shallow meridional overturning circulation, the Pacific Subtropical Cells (STC) that link the subtropical subduction and tropical upwelling in the Pacific. However, little is known about their impacts on the equatorial Pacific biogeochemistry, and decadal and interdecadal changes in the equatorial Pacific ecosystem structure and functioning. Here, we propose a combined study employing in situ and satellite data, and an advanced dynamic ecosystem model to answer two important scientific questions: (1) do the recharge-discharge processes associated with STC constructs offer a unifying mechanism for physical-biogeochemical interactions at decadal and longer time-scales in the equatorial Pacific? (2) are there significant decadal to inter-decadal changes, e.g., regime shifts, in ecosystem structure and productivity associated with the 1976/77 and 1998/99 phase shifts?

There have been extensive and growing databases of remotely sensed and in situ biogeochemical measurements, including chlorophyll and optical properties, which can be integrated with modeling studies. Our approach includes two major parts: (1) the use of in situ and satellite-based ocean color and associated data products for model calibration and validation, and (2) the analyses of modeled biological parameters during the period of 1950-2008. The objectives of the proposed study are to (1) to study how decadal to interdecadal variability of the physical processes regulate the biogeochemical processes, particularly nutrient transportation; (2) to study how past and present climate variability and change regulate the spatial distribution and temporal variability in the marine ecosystem structure (e.g., phytoplankton vs. zooplankton, and large cells vs. small cells); (3) to determine the magnitude of the regional primary and secondary productivity for the past 50 years, and the impacts of the marine ecosystem dynamics; and (4) to compare key biological parameters among three periods: 1950-1976, 1980-1996, and 1998-2008, and to determine if there are systematic shifts.

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More information about project Decadal Changes in the Equatorial Pacific Planktonic Ecosystem Structure and Functioning
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