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Radiative Impacts of Further Arctic Sea Ice Melt: Using past Observations to Inform Future Climate ImpactsThe Arctic region has seen dramatic changes over the past several decades, from polar amplification of global temperature rise to ecosystem changes to the decline of the sea ice. While there has been much speculation as to when the world will see an ice-free Arctic, the radiative impacts of an eventual disappearance of the Arctic sea ice are likely to be significant regardless of the timing. Using CERES radiation and microwave satellite sea ice data, Pistone et al (2014) estimated the radiative forcing due to albedo changes associated with the Arctic sea ice retreat over the 30 years of the satellite data record. In this study, we found that the Arctic Ocean saw a decrease in all-sky albedo of 4% (from 52% to 48%), for an estimated increase in solar heating of 6.4 W/m(exp 2) between 1979 and 2011, or 0.21 W/m(exp 2) when averaged over the globe. This value is substantial--approximately 25% as large as the forcing due to the change in CO2 during the same period. Here we update and expand upon this previous work and use the CERES broadband shortwave observations to explore the radiative impacts of a transition to completely ice-free Arctic Ocean. We estimate the annually-averaged Arctic Ocean planetary albedo under ice-free and cloud-free conditions to be 14% over the region, or approximately 25% lower in absolute terms than the Arctic Ocean cloud-free albedo in 1979. However, the question of all-sky conditions (i.e. including the effects of clouds) introduces a new level of complexity. We explore several cloud scenarios and the resultant impact on albedo. In each of these cases, the estimated forcing is not uniformly distributed throughout the year. We describe the relative contributions of ice loss by month as well as the spatial distributions of the resulting changes in absorbed solar energy. The seasonal timing and location—in addition to magnitude—of the altered solar absorption may have significant implications for atmospheric and ocean dynamics in the Arctic and at lower latitudes; this observationally-based estimate of the large-scale characteristics of an ice-free Arctic thus provides a valuable tool to complement and validate model-based assessments of future climate.
Document ID
20170007896
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Pistone, K.
(Universities Space Research Association Moffett Field, CA, United States)
Eisenman, I.
(California Univ. San Diego, CA, United States)
Ramanathan, V.
(California Univ. San Diego, CA, United States)
Date Acquired
August 21, 2017
Publication Date
July 16, 2017
Subject Category
Earth Resources And Remote Sensing
Report/Patent Number
ARC-E-DAA-TN44791
Meeting Information
Meeting: Radiation amd Climate - Gordan Research Conference
Location: Lewiston, ME
Country: United States
Start Date: July 16, 2017
End Date: July 21, 2017
Sponsors: Gordon Research Conferences, Inc.
Funding Number(s)
CONTRACT_GRANT: NNH15CO48B
Distribution Limits
Public
Copyright
Public Use Permitted.
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