SPATIAL AND TEMPORAL VARIABILITY OF GLOBAL WAVE PUMPING

Ocean waves traveling over continental shelves pump water and solutes between the water column and seabed aquifer at rates exceeding river discharge globally. Mixing of surface water and groundwater solutes results in high chemical reaction rates in the seabed aquifer. Thus, wave pumping rates and how those rates vary in space and time have implications for global chemical cycles. This study investigated wave pumping rates across the globe at high spatial (two-arcminute) and temporal (three-hour) resolutions between the years 2000 and 2010. Wave pumping was estimated across the shallow continental shelf (<200 m) analytically with four parameters: global bathymetry, seabed hydraulic conductivity estimated from seabed sediment data, and estimates of ocean wavelength and wave height derived from NOAA Wave Watch III hindcast models. Global wave pumping was estimated to average 1.67x10⁵ km³/yr, about twice the previous estimate (Riedl et al., 1972), which had been extrapolated from a small, calm shelf area. This rate is equivalent to a global ocean flushing time of 8.19x10³ years. Wave pumping rates averaged 0.58 m/yr and highly variable spatially, with yearly averages ranging from 0 to 6.73x10³ m/yr. The majority of wave pumping occurred in the Southern Hemisphere (62%), which contains 33% of shelf area, a discrepancy due to greater wave energy and higher K values in the Southern Hemisphere. Annually, wave pumping in both Northern and Southern Hemispheres was highest in autumn and lowest in spring. Over most of the globe, waves drive this variability, but ice cover is an important control on wave pumping in the Arctic and Southern Ocean. Comparison between wave pumping rates and a global ocean nutrient dataset showed wave pumping is generally higher in areas with high eutrophication potential in part because continental shelves are frequently wide in high-nutrient areas. These results provide an improved estimate of global wave pumping rates and describe variability over spatial and temporal scales, which give insight about potential hot spots and hot moments of biogeochemical activity in the seafloor.