Biogeochemical controls of surface ocean phosphate.

Area of Science:

• Oceanography
• Biogeochemistry
• Marine Ecosystems

Background:

• Surface ocean phosphate is often below detection limits, hindering understanding of its global distribution and ecological significance.
• Existing observational data and Earth system models (ESMs) provide an incomplete and often inaccurate view of marine phosphate levels.

Purpose of the Study:

• To compile and analyze high-sensitivity phosphate measurements to identify previously unrecognized low-phosphate regions.
• To evaluate the accuracy of ESMs in simulating surface ocean phosphate concentrations and their relationship with phytoplankton dynamics.
• To identify key drivers of surface ocean phosphate variability.

Main Methods:

• Global compilation of phosphate data using high-sensitivity analytical techniques.
• Comparison of compiled data with observational climatologies and Earth system model outputs.
• Analysis of model simulations to identify factors controlling phosphate concentrations.

Main Results:

• Identification of several previously unrecognized low-phosphate areas in the global ocean.
• Systematic overestimation of surface phosphate by both observational climatologies and ESMs.
• Misrepresentation of the relationships between phosphate, phytoplankton biomass, and primary productivity in ESMs.
• Demonstration that vertical nutrient supply ratios and lateral transport significantly influence phosphate concentrations.

Conclusions:

• Accurate quantification of marine nutrients, particularly phosphate, is crucial for understanding ocean ecosystem regulation.
• ESMs require improvement to accurately represent phosphate biogeochemistry and its impact on marine life.
• Understanding nutrient dynamics is essential for predicting ocean responses to future climate change.