ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-10-21683-2010 Effects of ship wakes on ocean brightness and radiative forcing over ocean Gatebe C. K. 1 2 Poudyal R. 2 3 Wilcox E. 2 5 Wang J. 2 4 Goddard Earth Sciences and Technology Center, University of Maryland, Baltimore County, Baltimore, Maryland 21228, USA NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA Science Systems and Applications, Inc., Lanham, Maryland 20706, USA University of Nebraska-Lincoln, 303 Bessey Hall Lincoln, Nebraska, 68588-0340, USA present address: Desert Research Institute, Reno, Nevada 89512, USA 17 09 2010 10 9 21683 21696 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/10/21683/2010/acpd-10-21683-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/10/21683/2010/acpd-10-21683-2010.pdf

Changes in surface albedo represent one of the main forcing agents that can counteract, to some extent, the positive forcing from increasing greenhouse gas concentrations. Here, we quantify the changes in ocean surface albedo from ship wakes and provide an estimate of radiative forcing over the global oceans. Our analysis is based on airborne radiation measurements over the Pacific Ocean near the California coast, where we determined that a ship wake increases reflected sunlight by more than 100% in some cases. Based on registered ships of 100 000 gross tonnage (GT), and assuming a global distribution of 30 000 ships, we estimated the global radiative forcing of ship wakes to be −0.003 Wm<sup>−2</sup>, which is comparable to the forcing of aircraft contrails, but not anticipated in the Intergovernmental Panel on Climate Change (IPCC) 2007 assessment report. From these results, we conclude that the climate impacts associated with ships will become more significant with growing ship traffic.

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