Winter Arctic sea ice thickness from ICESat-2: upgrades to freeboard and snow loading estimates and an assessment of the first three winters of data collection

A. A. Petty; A. A. Petty; N. Keeney; N. Keeney; A. Cabaj; P. Kushner; M. Bagnardi; M. Bagnardi

doi:10.5194/tc-17-127-2023

The Cryosphere (Jan 2023)

Winter Arctic sea ice thickness from ICESat-2: upgrades to freeboard and snow loading estimates and an assessment of the first three winters of data collection

A. A. Petty,
A. A. Petty,
N. Keeney,
N. Keeney,
A. Cabaj,
P. Kushner,
M. Bagnardi,
M. Bagnardi

Affiliations

A. A. Petty: Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
A. A. Petty: Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
N. Keeney: Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
N. Keeney: Earth System Science Interdisciplinary Center, University of Maryland, College Park, MD, USA
A. Cabaj: Department of Physics, University of Toronto, Toronto, Canada
P. Kushner: Department of Physics, University of Toronto, Toronto, Canada
M. Bagnardi: Cryospheric Sciences Laboratory, NASA Goddard Space Flight Center, Greenbelt, MD, USA
M. Bagnardi: ADNET Systems Inc., Bethesda, MD, USA

DOI: https://doi.org/10.5194/tc-17-127-2023
Journal volume & issue: Vol. 17
pp. 127 – 156

Abstract

Read online

NASA's ICESat-2 mission has provided near-continuous, high-resolution estimates of sea ice freeboard across both hemispheres since data collection started in October 2018. This study provides an impact assessment of upgrades to both the ICESat-2 freeboard data (ATL10) and NASA Eulerian Snow On Sea Ice Model (NESOSIM) snow loading on estimates of winter Arctic sea ice thickness. Misclassified leads were removed from the freeboard algorithm in the third release (rel003) of ATL10, which generally results in an increase in freeboards compared to rel002 data. The thickness increases due to increased freeboards in ATL10 improved comparisons of Inner Arctic Ocean sea ice thickness with thickness estimates from ESA's CryoSat-2. The upgrade from NESOSIM v1.0 to v1.1 results in only small changes in snow depth and density which have a less significant impact on thickness compared to the rel002 to rel003 ATL10 freeboard changes. The updated monthly gridded thickness data are validated against ice draft measurements obtained by upward-looking sonar moorings deployed in the Beaufort Sea, showing strong agreement (r2 of 0.87, differences of 11 ± 20 cm). The seasonal cycle in winter monthly mean Arctic sea ice thickness shows good agreement with various CryoSat-2 products (and a merged ICESat-2–CryoSat-2 product) and PIOMAS (Pan-Arctic Ice-Ocean Modeling and Assimilation System). Finally, changes in Arctic sea ice conditions over the past three winter seasons of data collection (November 2018–April 2021) are presented and discussed, including a 50 cm decline in multiyear ice thickness and negligible interannual differences in first-year ice. Interannual changes in snow depth provide a notable impact on the thickness retrievals on regional and seasonal scales. Our monthly gridded thickness analysis is provided online in a Jupyter Book format to increase transparency and user engagement with our ICESat-2 winter Arctic sea ice thickness data.

Published in The Cryosphere

ISSN: 1994-0416 (Print); 1994-0424 (Online)
Publisher: Copernicus Publications
Country of publisher: Germany
LCC subjects: Geography. Anthropology. Recreation: Environmental sciences; Science: Geology
Website: http://www.the-cryosphere.net/

About the journal