Identifying the processes controlling the distribution of H₂O₂ in surface waters along a meridional transect in the eastern Atlantic

Hydrogen peroxide (H₂O₂) is an important oxidant for many bio-relevant trace metals and organic compounds and has potential as a tracer for mixing in near surface waters. In this study we combine H₂O₂ and bio-optical measurements with satellite data for a meridional transect from 46°N to 26°S in the eastern Atlantic in order to determine the key processes affecting its distribution. Surface H₂O₂ ranged from 21-123 nmol L^-1, with maximum inventories (0-200 m) of 5.5-5.9 mmol m^-2 found at 30°N and 25°S. Analyses showed a strong positive correlation of surface H₂O₂ with daily irradiances and recent precipitation, though poor correlations with CDOM suggest sunlight is the limiting reactant for H₂O₂ formation. Vertical distributions of H₂O₂ were controlled by a combination of mixing processes and phytoplankton activity. The present study highlights processes controlling global H₂O₂ distributions and points towards the development of parameterization schemes for prediction via satellite data.