Articles | Volume 19, issue 10
https://doi.org/10.5194/tc-19-4805-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-19-4805-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
21 Oct 2025
Research article |
| 21 Oct 2025
| 21 Oct 2025
Sea ice concentration estimates from ICESat-2 linear ice fraction – Part 1: Multi-sensor comparison of sea ice concentration products
Department of Earth Science and Environmental Change, University of Illinois Urbana-Champaign, Urbana, IL, USA
Christopher Horvat
Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
Pittayuth Yoosiri
Department of Atmospheric and Oceanic Science, University of Maryland, College Park, MD, USA
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Christopher Horvat, Ellen Buckley, and Madelyn Stewart
The Cryosphere, 19, 4819–4833, https://doi.org/10.5194/tc-19-4819-2025, https://doi.org/10.5194/tc-19-4819-2025, 2025
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Since the late 1970s, standard methods for observing sea ice area from satellites have contrasted its passive microwave emissions to those of the ocean. Since 2018, a new satellite, ICESat-2, may have offered a unique and independent way to sample sea ice area at high skill and resolution, using laser altimetry. We develop a new product of sea ice area for the Arctic using ICESat-2 and constrain the biases associated with the use of altimetry instead of passive microwave emissions.
Ellen M. Buckley, Leela Cañuelas, Mary-Louise Timmermans, and Monica M. Wilhelmus
The Cryosphere, 18, 5031–5043, https://doi.org/10.5194/tc-18-5031-2024, https://doi.org/10.5194/tc-18-5031-2024, 2024
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Arctic sea ice cover evolves seasonally from large plates separated by long, linear leads in the winter to a mosaic of smaller sea ice floes in the summer. Here, we present a new image segmentation algorithm applied to thousands of images and identify over 9 million individual pieces of ice. We observe the characteristics of the floes and how they evolve throughout the summer as the ice breaks up.
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The decline of sea ice area variability is a leading indicator of climate change, and accurate measurement of sea ice area are of high importance. We develop new measurement of sea ice area coverage using the ICESat-2 laser altimeter, typically used to measure the height of the ice surface. The new method performs as well or better than typical passive microwave measurements, especially for sea ice populated with thin fractures in winter.
Ellen M. Buckley, Sinéad L. Farrell, Ute C. Herzfeld, Melinda A. Webster, Thomas Trantow, Oliwia N. Baney, Kyle A. Duncan, Huilin Han, and Matthew Lawson
The Cryosphere, 17, 3695–3719, https://doi.org/10.5194/tc-17-3695-2023, https://doi.org/10.5194/tc-17-3695-2023, 2023
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In this study, we use satellite observations to investigate the evolution of melt ponds on the Arctic sea ice surface. We derive melt pond depth from ICESat-2 measurements of the pond surface and bathymetry and melt pond fraction (MPF) from the classification of Sentinel-2 imagery. MPF increases to a peak of 16 % in late June and then decreases, while depth increases steadily. This work demonstrates the ability to track evolving melt conditions in three dimensions throughout the summer.
Christopher Horvat, Ellen Buckley, and Madelyn Stewart
The Cryosphere, 19, 4819–4833, https://doi.org/10.5194/tc-19-4819-2025, https://doi.org/10.5194/tc-19-4819-2025, 2025
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Since the late 1970s, standard methods for observing sea ice area from satellites have contrasted its passive microwave emissions to those of the ocean. Since 2018, a new satellite, ICESat-2, may have offered a unique and independent way to sample sea ice area at high skill and resolution, using laser altimetry. We develop a new product of sea ice area for the Arctic using ICESat-2 and constrain the biases associated with the use of altimetry instead of passive microwave emissions.
Aikaterini Tavri, Chris Horvat, Brodie Pearson, Guillaume Boutin, Anne Hansen, and Ara Lee
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In the Arctic, thin sea ice lets ocean waves travel into ice-covered areas. When waves, wind, and currents interact, they create Langmuir turbulence—strong mixing near the surface that helps move heat, gases, and nutrients between the ocean and air. Scientists understand this process in open water, but not well in polar regions. This study uses a new wave–ice model to find out where and how Langmuir turbulence affects ocean mixing in the Arctic.
Ellen M. Buckley, Leela Cañuelas, Mary-Louise Timmermans, and Monica M. Wilhelmus
The Cryosphere, 18, 5031–5043, https://doi.org/10.5194/tc-18-5031-2024, https://doi.org/10.5194/tc-18-5031-2024, 2024
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Arctic sea ice cover evolves seasonally from large plates separated by long, linear leads in the winter to a mosaic of smaller sea ice floes in the summer. Here, we present a new image segmentation algorithm applied to thousands of images and identify over 9 million individual pieces of ice. We observe the characteristics of the floes and how they evolve throughout the summer as the ice breaks up.
Momme C. Hell and Christopher Horvat
The Cryosphere, 18, 341–361, https://doi.org/10.5194/tc-18-341-2024, https://doi.org/10.5194/tc-18-341-2024, 2024
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Sea ice is heavily impacted by waves on its margins, and we currently do not have routine observations of waves in sea ice. Here we propose two methods to separate the surface waves from the sea-ice height observations along each ICESat-2 track using machine learning. Both methods together allow us to follow changes in the wave height through the sea ice.
Christopher Horvat, Ellen Buckley, Madelyn Stewart, Poom Yoosiri, and Monica M. Wilhelmus
EGUsphere, https://doi.org/10.5194/egusphere-2023-2312, https://doi.org/10.5194/egusphere-2023-2312, 2023
Preprint withdrawn
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The decline of sea ice area variability is a leading indicator of climate change, and accurate measurement of sea ice area are of high importance. We develop new measurement of sea ice area coverage using the ICESat-2 laser altimeter, typically used to measure the height of the ice surface. The new method performs as well or better than typical passive microwave measurements, especially for sea ice populated with thin fractures in winter.
Ellen M. Buckley, Sinéad L. Farrell, Ute C. Herzfeld, Melinda A. Webster, Thomas Trantow, Oliwia N. Baney, Kyle A. Duncan, Huilin Han, and Matthew Lawson
The Cryosphere, 17, 3695–3719, https://doi.org/10.5194/tc-17-3695-2023, https://doi.org/10.5194/tc-17-3695-2023, 2023
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In this study, we use satellite observations to investigate the evolution of melt ponds on the Arctic sea ice surface. We derive melt pond depth from ICESat-2 measurements of the pond surface and bathymetry and melt pond fraction (MPF) from the classification of Sentinel-2 imagery. MPF increases to a peak of 16 % in late June and then decreases, while depth increases steadily. This work demonstrates the ability to track evolving melt conditions in three dimensions throughout the summer.
Yanan Wang, Byongjun Hwang, Adam William Bateson, Yevgeny Aksenov, and Christopher Horvat
The Cryosphere, 17, 3575–3591, https://doi.org/10.5194/tc-17-3575-2023, https://doi.org/10.5194/tc-17-3575-2023, 2023
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Sea ice is composed of small, discrete pieces of ice called floes, whose size distribution plays a critical role in the interactions between the sea ice, ocean and atmosphere. This study provides an assessment of sea ice models using new high-resolution floe size distribution observations, revealing considerable differences between them. These findings point not only to the limitations in models but also to the need for more high-resolution observations to validate and calibrate models.
Jill Brouwer, Alexander D. Fraser, Damian J. Murphy, Pat Wongpan, Alberto Alberello, Alison Kohout, Christopher Horvat, Simon Wotherspoon, Robert A. Massom, Jessica Cartwright, and Guy D. Williams
The Cryosphere, 16, 2325–2353, https://doi.org/10.5194/tc-16-2325-2022, https://doi.org/10.5194/tc-16-2325-2022, 2022
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The marginal ice zone is the region where ocean waves interact with sea ice. Although this important region influences many sea ice, ocean and biological processes, it has been difficult to accurately measure on a large scale from satellite instruments. We present new techniques for measuring wave attenuation using the NASA ICESat-2 laser altimeter. By measuring how waves attenuate within the sea ice, we show that the marginal ice zone may be far wider than previously realised.
Christopher Horvat and Lettie A. Roach
Geosci. Model Dev., 15, 803–814, https://doi.org/10.5194/gmd-15-803-2022, https://doi.org/10.5194/gmd-15-803-2022, 2022
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Sea ice is a composite of individual pieces, called floes, ranging in horizontal size from meters to kilometers. Variations in sea ice geometry are often forced by ocean waves, a process that is an important target of global climate models as it affects the rate of sea ice melting. Yet directly simulating these interactions is computationally expensive. We present a neural-network-based model of wave–ice fracture that allows models to incorporate their effect without added computational cost.
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Short summary
Sea ice coverage is a key indicator of changes in polar and global climate. There is a long (over 40 years) record of sea ice concentration and area from passive microwave measurements. In this work we show the biases in these data based on high-resolution imagery. We also suggest the use of ICESat-2, a high- resolution satellite laser, that can supplement the passive microwave estimates.
Sea ice coverage is a key indicator of changes in polar and global climate. There is a long...
