Improved SSM/I Thin Ice Algorithm with Ice Type Discrimination in Coastal Polynyas

Kashiwase, Haruhiko; Ohshima, Κay I.; Nakata, Kazuyoshi; Tamura, Takeshi

doi:10.1175/jtech-d-20-0145.1

Cited by 6 publications

(5 citation statements)

References 58 publications

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“…Thin SIT is also now routinely estimated from passive microwaves at 1.4 GHz (Kaleschke et al., 2016). Efforts are also conducted to estimate thin SIT with higher frequencies (18 and 36 GHz) (e.g., Yoshizawa et al., 2018 or Kashiwase et al., 2021). However, evaluation of the potential of the PMW observations to estimate the SIT for the full thickness range has not triggered yet much efforts, as PMW observations are not expected to penetrate the ice for more than 50 cm, and to be directly sensitive to the thicker sea ice, especially at high frequency (Heygster et al., 2014).…”

Section: Introductionmentioning

confidence: 99%

Arctic Sea Ice Thickness Estimation From Passive Microwave Satellite Observations Between 1.4 and 36 GHz

Soriot

Prigent

Jiménez³

et al. 2023

Earth and Space Science

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Arctic sea ice thickness (SIT) has been mostly retrieved from lidar and radar altimeters since the 2000s. However, the repeatability of altimeters and their spatial coverage limit SIT estimates spatially and temporally. On the other hand, the passive microwave (PMW) radiometers have daily basin‐scale coverage of the Arctic. In this study, we propose a SIT retrieval from PMW observations, derived from a statistical inversion technique. It is based on the evidence of high correlations between PMW observations and existing altimetric satellite‐derived SIT, especially at 36 GHz. Lidar ICESat‐2 SIT products are used to train a neural network with multiple combinations of brightness temperatures between 1.4 and 36 GHz as inputs over the 2018–2019 time period. The PMW retrieved SIT can mimic the lidar SIT product over the full winter over the Arctic, with a correlation of 0.85, and a root mean square difference (RMSD) of 0.54 cm. Results are also compared with the SIT product CS2SMOS (CryoSat‐2 and Soil Moisture Ocean Salinity merged product), with SIT from a coupled ice/ocean reanalysis model and with the Operation IceBridge QuickLook airborne SIT measurements. The PMW SIT retrieval with all frequencies from 1.4 to 36 GHz shows a correlation of 0.72 and a RMSD of 57 cm when compared to OIB‐QL measurements, for large SIT (mostly above 3 m), under multi‐year ice environments. The PMW SIT retrieval using only 18 and 36 GHz has similar performances and could allow the calculation of long time series, these microwave frequencies being available from satellites since the 1980s.

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Section: Introductionmentioning

confidence: 99%

Arctic Sea Ice Thickness Estimation From Passive Microwave Satellite Observations Between 1.4 and 36 GHz

Soriot

Prigent

Jiménez³

et al. 2023

Earth and Space Science

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“…As one improved approach, Kashiwase et al. (2019, 2021) developed an algorithm that accounts for three types of thin sea ice (active frazil, thin solid ice, and a mixture of two types).…”

Section: Discussionmentioning

confidence: 99%

“…For more accurate estimates of sea ice production, these error sources need to be taken into account in the thin ice thickness algorithm in future. As one improved approach, Kashiwase et al (2019Kashiwase et al ( , 2021 developed an algorithm that accounts for three types of thin sea ice (active frazil, thin solid ice, and a mixture of two types).…”

Section: Discussionmentioning

confidence: 99%

Mapping of Active Frazil and Sea Ice Production in the Northern Hemisphere, With Comparison to the Southern Hemisphere

Nakata

Ohshima

2022

JGR Oceans

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Frazil ice in the coastal polynyas has been increasingly recognized as important for efficient sea ice production, associated dense water formation, transport of particulate matter and consequent biological production. However, it has not been well understood where and to what degree active‐frazil areas occur in the Northern Hemisphere polynyas. We presented the first mapping of active frazil in the Northern Hemisphere, using sea ice data during September–May for 2002/2003–2010/2011, created from an Advanced Microwave Scanning Radiometer for the Earth Observing System thin ice algorithm that can detect active frazil areas. The North Water, Northeast Water, Anadyr, and St. Lawrence Island polynyas were found to have a relatively high occurrence rate of active frazil compared with other polynyas. We improved the estimation of sea ice production by discriminating between active frazil and thin solid ice and found that previous algorithms tended to overestimate sea ice production, particularly for polynyas dominated by thin solid ice such as the Okhotsk Northwestern polynya. We also made the first global comparison of polynya characteristics for all the major coastal polynyas. The annual ice production rate is 3–4 m yr−1 in the Northern Hemisphere polynyas and 6–9 m yr−1 in the Antarctic coastal polynyas. This large difference is mainly explained by the less frequent occurrence of active frazil and thin ice areas in the Northern Hemisphere polynyas owing to a lower occurrence of strong wind events.

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“…The underwater frazil ice formation prevents heat-insulating surface-cover ice from forming, thereby enabling efficient ice production. A thin ice algorithm that detects active frazil, a mixture of frazil/pancake ice and open water, has been developed for AMSR-E (Nakata et al, 2019) and SSM/I (Kashiwase et al, 2021), which provides a more accurate estimation of sea ice formation. Figure 2B shows the updated map of sea ice formation based on that algorithm.…”

Section: Remote Sensingmentioning

confidence: 99%

Observing Antarctic Bottom Water in the Southern Ocean

Silvano,

Purkey,

Gordon

et al. 2023

Front. Mar. Sci.

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Dense, cold waters formed on Antarctic continental shelves descend along the Antarctic continental margin, where they mix with other Southern Ocean waters to form Antarctic Bottom Water (AABW). AABW then spreads into the deepest parts of all major ocean basins, isolating heat and carbon from the atmosphere for centuries. Despite AABW’s key role in regulating Earth’s climate on long time scales and in recording Southern Ocean conditions, AABW remains poorly observed. This lack of observational data is mostly due to two factors. First, AABW originates on the Antarctic continental shelf and slope where in situ measurements are limited and ocean observations by satellites are hampered by persistent sea ice cover and long periods of darkness in winter. Second, north of the Antarctic continental slope, AABW is found below approximately 2 km depth, where in situ observations are also scarce and satellites cannot provide direct measurements. Here, we review progress made during the past decades in observing AABW. We describe 1) long-term monitoring obtained by moorings, by ship-based surveys, and beneath ice shelves through bore holes; 2) the recent development of autonomous observing tools in coastal Antarctic and deep ocean systems; and 3) alternative approaches including data assimilation models and satellite-derived proxies. The variety of approaches is beginning to transform our understanding of AABW, including its formation processes, temporal variability, and contribution to the lower limb of the global ocean meridional overturning circulation. In particular, these observations highlight the key role played by winds, sea ice, and the Antarctic Ice Sheet in AABW-related processes. We conclude by discussing future avenues for observing and understanding AABW, impressing the need for a sustained and coordinated observing system.

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Improved SSM/I Thin Ice Algorithm with Ice Type Discrimination in Coastal Polynyas

Cited by 6 publications

References 58 publications

Arctic Sea Ice Thickness Estimation From Passive Microwave Satellite Observations Between 1.4 and 36 GHz

Arctic Sea Ice Thickness Estimation From Passive Microwave Satellite Observations Between 1.4 and 36 GHz

Mapping of Active Frazil and Sea Ice Production in the Northern Hemisphere, With Comparison to the Southern Hemisphere

Observing Antarctic Bottom Water in the Southern Ocean

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