Arctic sea ice albedo: Spectral composition, spatial heterogeneity, and temporal evolution observed during the MOSAiC drift

Abstract

The magnitude, spectral composition, and variability of the Arctic sea ice surface albedo are key to understanding and numerically simulating Earth’s shortwave energy budget. Spectral and broadband albedos of Arctic sea ice were spatially and temporally sampled by on-ice observers along individual survey lines throughout the sunlit season (April–September, 2020) during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. The seasonal evolution of albedo for the MOSAiC year was constructed from spatially averaged broadband albedo values for each line. Specific locations were identified as representative of individual ice surface types, including accumulated dry snow, melting snow, bare and melting ice, melting and refreezing ponded ice, and sediment-laden ice. The area-averaged seasonal progression of total albedo recorded during MOSAiC showed remarkable similarity to that recorded 22 years prior on multiyear sea ice during the Surface Heat Budget of the Arctic Ocean (SHEBA) expedition. In accord with these and other previous field efforts, the spectral albedo of relatively thick, snow-free, melting sea ice shows invariance across location, decade, and ice type. In particular, the albedo of snow-free, melting seasonal ice was indistinguishable from that of snow-free, melting second-year ice, suggesting that the highly scattering surface layer that forms on sea ice during the summer is robust and stabilizing. In contrast, the albedo of ponded ice was observed to be highly variable at visible wavelengths. Notable temporal changes in albedo were documented during melt and freeze onset, formation and deepening of melt ponds, and during melt evolution of sediment-laden ice. While model simulations show considerable agreement with the observed seasonal albedo progression, disparities suggest the need to improve how the albedo of both ponded ice and thin, melting ice are simulated.

Regional Geoengineering Using Tiny Glass Bubbles Would Accelerate the Loss of Arctic Sea Ice

“…Nilas with a thin snow cover has an albedo of 0.44. Snow-free melting sea ice has a substantially higher albedo (0.62) due to the presence of the SSL (Light et al, 2008(Light et al, , 2015(Light et al, , 2022.…”

“…Some of these values come from previously published work (Brandt et al., 2005; Zatko & Warren, 2015). Others were calculated using measurements of spectral albedo shown in Figure 2, some of which were made on two Arctic expeditions: (a) the Multidisciplinary drifting Observatory for the Study of Arctic Climate (Light et al., 2022; Smith et al., 2021), and (b) NASA's Impacts of Climate on the Eco‐Systems and Chemistry of the Arctic Pacific Environment (Light et al., 2015). In these calculations, the visible (0.3–0.7 μm) and NIR (0.7–2.5 μm) band albedos were first determined and then weighted using the normalized solar spectra for clear and overcast sky conditions (Grenfell & Perovich, 2008) to produce the broadband (0.3–2.5 μm) albedo.…”

“…Spectral albedos from in-situ measurements. The values for melting sea ice, melt ponds, and refrozen melt ponds are from the Impacts of Climate on the Eco-Systems and Chemistry of the Arctic Pacific Environment(Light et al, 2015) and Multidisciplinary drifting Observatory for the Study of Arctic Climate(Light et al, 2022;Smith et al, 2021) expeditions. The values for thick cold snow are fromHudson et al (2006); the remaining values are fromBrandt et al (2005) andZatko and Warren (2015).…”

Observing the Evolution of Summer Melt on Multiyear Sea Ice with ICESat-2 and Sentinel-2

“…During the summer, highly reflective snow covered Arctic sea ice with an albedo > 0.7 decreases due to both the disintegration of the ice cover exposing the low-albedo open ocean (albedo < 0.1) and melt ponding on the ice surface (albedo 0.1 to 0.3) (Perovich and Polashenski, 2012;Light et al, 2022). This rapid change in albedo drives the positive ice albedo feedback (Curry et al, 1995), enabling additional uptake of shortwave radiation, enhancing melt.…”

Sea Ice Melt Pond Fraction Derived From Sentinel‐2 Data: Along the MOSAiC Drift and Arctic‐Wide

“…Typical values of MPFs in summer in the central Arctic range from 15% to 40% (Istomina, Heygster, Huntemann, Marks, et al., 2015; Rösel & Kaleschke, 2011). Melt ponds on sea ice significantly reduce its broadband and spectral albedo (Light et al., 2022; Malinka et al., 2018) affecting the heat and mass balance due to an increase of solar absorption within and an enhancement of transmission through the ice into the Arctic Ocean (Light et al., 2008; Nicolaus et al., 2012). However, global climate models still lack a comprehensive representation of melt ponds (Dorn et al., 2018; Hunke et al., 2013; Zhang et al., 2018).…”