Measurements of bubble size spectra within leads in the Arctic summer pack ice

The first measurements of bubble size spectra within the near-surface waters of open leads in the central Arctic pack ice were obtained during the Arctic Summer Cloud-Ocean Study (ASCOS) in August 2008 at 87-87.6° N, 1-11° W. A significant number of small bubbles (30-100 μm diameter) were present, with concentration decreasing rapidly with size from 100-560 μm; no bubbles larger than 560 μm were observed. The bubbles were present both during periods of low wind speed (U<6 m s -1) and when ice covered the surface of the lead. The low wind and short open-water fetch precludes production of bubbles by wave breaking suggesting that the bubbles are generated by processes below the surface. When the surface water was open to the atmosphere bubble concentrations increased with increasing heat loss to the atmosphere. The presence of substantial numbers of bubbles is significant because the bursting of bubbles at the surface provides a mechanism for the generation of aerosol and the ejection of biological material from the ocean into the atmosphere. Such a transfer has previously been proposed as a potential climate feedback linking marine biology and Arctic cloud properties.