Global sea-surface iodide observations, 1967-2018

Abstract

The marine iodine cycle has significant impacts on air quality and atmospheric chemistry. Specifically, the reaction of iodide with ozone in the top few micrometres of the surface ocean is an important sink for tropospheric ozone (a pollutant gas) and the dominant source of reactive iodine to the atmosphere. Sea surface iodide parameterisations are now being implemented in air quality models, but these are currently a major source of uncertainty. Relatively little observational data is available to estimate the global surface iodide concentrations, and this data has not hitherto been openly available in a collated, digital form. Here we present all available sea surface (<20 m depth) iodide observations. The dataset includes values digitised from published manuscripts, published and unpublished data supplied directly by the originators, and data obtained from repositories. It contains 1342 data points, and spans latitudes from 70°S to 68°N, representing all major basins. The data may be used to model sea surface iodide concentrations or as a reference for future observations.

Fig. 1

Locations of iodide observations included in our dataset. New data reported here is in red and existing data from Chance et al. is blue. Figure produced with Python Matplotlib.

Fig. 2

Estimated probability density function (PDF; kernel density estimate) for sea surface iodide observations. Plot shows all data (blue) combined, and open ocean (green) and coastal (red) data treated separately. Expanded inset shows values <400 nM only. Figure produced with Python Matplotlib and Seaborn packages.