Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo

Irvine-Fynn, Tristram D. L.; Bunting, Pete; Cook, Joseph M.; Hubbard, Alun; Barrand, Nicholas E.; Hanna, Edward; Hardy, Andy J.; Hodson, Andrew J.; Holt, Tom O.; Huss, Matthias; McQuaid, James B.; Nilsson, Johan; Naegeli, Kathrin; Roberts, Osian; Ryan, Jonathan C.; Tedstone, Andrew J.; Tranter, Martyn; Williamson, Christopher J. (2022). Temporal Variability of Surface Reflectance Supersedes Spatial Resolution in Defining Greenland’s Bare-Ice Albedo. Remote sensing, 14(1), p. 62. Molecular Diversity Preservation International MDPI 10.3390/rs14010062

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Ice surface albedo is a primary modulator of melt and runoff, yet our understanding of how reflectance varies over time across the Greenland Ice Sheet remains poor. This is due to a disconnect between point or transect scale albedo sampling and the coarser spatial, spectral and/or temporal resolutions of available satellite products. Here, we present time-series of bare-ice surface reflectance data that span a range of length scales, from the 500 m for Moderate Resolution Imaging Spectrometer’s MOD10A1 product, to 10 m for Sentinel-2 imagery, 0.1 m spot measurements from ground-based field spectrometry, and 2.5 cm from uncrewed aerial drone imagery. Our results reveal broad similarities in seasonal patterns in bare-ice reflectance, but further analysis identifies short-term dynamics in reflectance distribution that are unique to each dataset. Using these distributions, we demonstrate that areal mean reflectance is the primary control on local ablation rates, and that the spatial distribution of specific ice types and impurities is secondary. Given the rapid changes in mean reflectance observed in the datasets presented, we propose that albedo parameterizations can be improved by (i) quantitative assessment of the representativeness of time-averaged reflectance data products, and, (ii) using temporally-resolved functions to describe the variability in impurity distribution at daily time-scales. We conclude that the regional melt model performance may not be optimally improved by increased spatial resolution and the incorporation of sub-pixel heterogeneity, but instead, should focus on the temporal dynamics of bare-ice albedo.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Institute of Geography > Physical Geography > Unit Climatology
10 Strategic Research Centers > Oeschger Centre for Climate Change Research (OCCR)
08 Faculty of Science > Institute of Geography
08 Faculty of Science > Institute of Geography > Physical Geography

UniBE Contributor:

Naegeli, Kathrin

Subjects:

500 Science > 550 Earth sciences & geology
900 History > 910 Geography & travel

ISSN:

2072-4292

Publisher:

Molecular Diversity Preservation International MDPI

Language:

English

Submitter:

Kathrin Naegeli

Date Deposited:

04 Feb 2022 13:30

Last Modified:

04 Feb 2022 13:30

Publisher DOI:

10.3390/rs14010062

BORIS DOI:

10.48350/164607

URI:

https://boris.unibe.ch/id/eprint/164607

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