The intensifying role of high wind speeds on gas transfer velocities and air-sea carbon dioxide fluxes
Abstract
The imprint of air flow over interfaces of water, sand, and snow has fascinated scientists and general observers alike as evidenced by the popularity of the photographs by Cornish to the Royal Meteorological Society in London in 1909. The quantitative description of this imprint, especially in the air-sea system, soon followed. While it has been known that wave breaking and bubble generation at high wind speeds could enhance air-sea CO2 exchange rates (F), quantification of their contribution remains a formidable challenge and progress on this front is urgently needed in climate sciences. This is especially important considering that over the last three decades, a significant uptick in both the magnitude and frequency of high wind events (HW) has been documented by satellite observations. Using a recently published wind-wave dependent expression for gas transfer velocity (K) that explicitly considers bubbles and a widely used wind only parameterization, the implications of this uptick is assessed over time and space. The calculations reveal a surprising spatial pattern of K at high wind speeds (KHW) that is determined by spatial variations of time-averaged sea surface temperature. However, the increasing trend in KHW over many of the global oceans appears to be dominated by trends in high wind speeds. The high wind speed events, which represent on average 3% of wind conditions, contribute disproportionally to the global F (17.5%) with an increasing trend in contribution over the last three decades. Approximately 50% of the global F at high wind speeds is attributed to the bubbles' contribution to air-sea CO2 flux. Because the highest trends in KHW occur in regions of deep-water formations such as the North Atlantic and Southern Ocean, the findings here are of significance to quantifying CO2 transfer to the ocean interior.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMOS048..08G
- Keywords:
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- 4504 Air/sea interactions;
- OCEANOGRAPHY: PHYSICAL;
- 4512 Currents;
- OCEANOGRAPHY: PHYSICAL;
- 4520 Eddies and mesoscale processes;
- OCEANOGRAPHY: PHYSICAL;
- 4560 Surface waves and tides;
- OCEANOGRAPHY: PHYSICAL