Sensitivity of the Arctic Sea Ice Cover to the Summer Surface Scattering Layer. Issue 9 (5th May 2022)

• Record Type: Journal Article
• Authors: Smith, Madison M.; Light, Bonnie; Macfarlane, Amy R.; Perovich, Don K.; Holland, Marika M.; Shupe, Matthew D.
• Is Part Of: Geophysical research letters. Volume 49:Issue 9(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-05-05
• Subjects: sea ice -- MOSAiC -- Arctic -- albedo; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL098349
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: The "surface scattering layer" (SSL) is the highly‐scattering, coarse‐grained ice layer that forms on the surface of melting, drained sea ice during spring and summer. Ice of sufficient thickness with an SSL has an observed persistent broadband albedo of ∼0.65, resulting in a strong influence on the regional solar partitioning. Experiments during the Multidisciplinary drifting Observatory for the Study of the Arctic Climate expedition showed that the SSL re‐forms in approximately 1 day following manual removal. Coincident spectral albedo measurements provide insight into the SSL evolution, where albedo increased on sunny days with higher solar insolation. Comparison with experiments in radiative transfer and global climate models show that the sea ice albedo is greatly impacted by the SSL thickness. The presence of SSL is a significant component of the ice‐albedo feedback, with an albedo impact of the same order as melt ponds. Changes in SSL and implications for Arctic sea ice within a warming climate are uncertain. Plain Language Summary: During the summer melt season, the surface of Arctic sea ice generally transforms into a crumbly, snow‐like layer that is known as the "surface scattering layer" (SSL). As the name implies, it is highly‐scattering, resulting in a high reflectivity where typically around 65% of incoming solar energy is reflected. However, this value has been observed to be lower, particularly when the layer is relatively thin, and there is very little known about what controls its variability. We completed experiments on summer sea ice to observe what happens when the layer is completely removed. We completed similar experiments in models, where we were able to simulate the expected reflectivity over a range of layer thicknesses, and then see what the expected impact on Arctic sea ice would be with complete removal. We find that removal of this layer dramatically reduces sea ice albedo and Arctic sea ice volume. The SSL is an under‐appreciated feature of Arctic sea ice, and more work to understand its variability in a warming Arctic is needed. Key Points: Surface scattering layer (SSL) is a persistent feature of bare, melting sea ice that is central to the sea ice‐albedo feedback Observations and modeling both show sea ice albedo sensitivity to SSL thickness Models represent the optical properties of the SSL layer as a function of ice thickness only, but these properties also vary with morphology