Consolidating ICESat-2 Ocean Wave Characteristics with CryoSat-2 during the CRYO2ICE Campaign

Bjarke Nilsson,Heidi Ranndal,Ole Baltazar Andersen,Mikkel Lydholm Rasmussen

doi:10.3390/rs14061300

Abstract

Using the Ice, Cloud, and land Elevation Satellite 2 (ICESat-2) global high-resolution elevation measurements, it is possible to distinguish individual surface ocean waves. With the vast majority of ocean surveying missions using radar satellites, ICESat-2 observations are an important addition to ocean surveys. ICESat-2 can also provide additional observations not possible with radar. In this paper, we consolidate the ICESat-2 ocean observations by comparing the significant wave height (SWH) with coincident CryoSat-2 radar observations during the CRYO2ICE campaign from August 2020 to August 2021. We use 136 orbit segments, constrained to the Pacific and Atlantic oceans as well as the Bering Sea, to compare observations to show the level of agreement between these systems. Three models based on ICESat-2 are used in the comparison: the standard ocean data output (ATL12), a method of modeling the individual surface waves using the geolocated photons and, functioning as a baseline, an approach using the standard deviation of the ocean surface. We find the following correlations between the SWHs from the models and the SWHs from CryoSat-2: 0.97 for ATL12, 0.95 for the observed waves model, and 0.97 for the standard deviation model. In the same comparison, we find mean differences relative to the observed SWHs for each model, as well as errors, which increase as the SWH increases. The SWH observed from ICESat-2 is found to agree with observations from CryoSat-2, with limitations due to changes in the sea state between the satellite observations. Observing the individual surface waves from ICESat-2 can therefore provide additional observed properties of the sea state that can be used alongside other global observations.

Highlights

Accepted: 6 March 2022Observing ocean surface waves is a key element in several fields, from understanding the underlying mechanics of waves in climatology to risk assessment in marine engineering [1]
Comparisons between the significant wave height (SWH) determined from CryoSat-2 and the ICESat-2 derived models are presented
ATL12 in this paper, we found that ATL12 has a more negative bias when it is compared to CryoSat-2

Summary

Introduction

Accepted: 6 March 2022Observing ocean surface waves is a key element in several fields, from understanding the underlying mechanics of waves in climatology to risk assessment in marine engineering [1]. The ability to predict the behavior of ocean waves has increased over the past years due to the use of satellite-based observations [1]. The behavior of ocean waves is complex, and most of them would be too inaccessible for monitoring if not for these space-based altimetry missions. Since TOPEX/Poseidon launched in 1992, the majority of the ocean observation satellites have been using radar altimeters, with more modern missions increasing in precision, which has helped to map the ocean’s surface. To be able to use these observations in addition to the observations from multi-year missions based on radar altimeters, this method must be compared to current methods. Sea surface height anomalies of the Arctic Ocean from ICESat-2: A first examination and comparisons with CryoSat-2.

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Discussion

Conclusion