Automatic Measurement of Polynya Area by Anisotropic Filtering and Markov Random Fields

Moctezuma-Flores, Miguel; Parmiggiani, F.; Lopez, Ludwin Lopez

doi:10.1109/jstars.2014.2314684

Cited by 10 publications

(4 citation statements)

References 26 publications

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“…Due to the manually digitizing, the data sets are not easy to be reproduced or automatically extracted. Automated methods have been developed to identify the polynya area based on COSMO-SkyMed X-SAR and ERS C-SAR data [40,41,53,54], and the results showed high agreement with manual results. However, these methods have not yet been used to derive time series of polynya areas, and are not applied in the condition that the polynya extent/outline in the gap days obtained, totally based on visual observation and experiences, from the images after the gap days.…”

Section: Discussionmentioning

confidence: 86%

Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images

et al. 2020

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High sea ice production (SIP) generates high-salinity water, thus, influencing the global thermohaline circulation. Estimation from passive microwave data and heat flux models have indicated that the Ross Ice Shelf polynya (RISP) may be the highest SIP region in the Southern Oceans. However, the coarse spatial resolution of passive microwave data limited the accuracy of these estimates. The Sentinel-1 Synthetic Aperture Radar dataset with high spatial and temporal resolution provides an unprecedented opportunity to more accurately distinguish both polynya area/extent and occurrence. In this study, the SIPs of RISP and McMurdo Sound polynya (MSP) from 1 March–30 November 2017 and 2018 are calculated based on Sentinel-1 SAR data (for area/extent) and AMSR2 data (for ice thickness). The results show that the wind-driven polynyas in these two years occurred from the middle of March to the middle of November, and the occurrence frequency in 2017 was 90, less than 114 in 2018. However, the annual mean cumulative SIP area and volume in 2017 were similar to (or slightly larger than) those in 2018. The average annual cumulative polynya area and ice volume of these two years were 1,040,213 km2 and 184 km3 for the RSIP, and 90,505 km2 and 16 km3 for the MSP, respectively. This annual cumulative SIP (volume) is only 1/3–2/3 of those obtained using the previous methods, implying that ice production in the Ross Sea might have been significantly overestimated in the past and deserves further investigations.

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Section: Discussionmentioning

confidence: 86%

Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images

et al. 2020

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“…Accordingly, by applying a simple masking, the total polynya area is estimated to be 1030 km 2 , where 287 km 2 out of 1030 km 2 are covered by thin sea ice, see Table III. This means that the polynya, usually assumed as a homogeneous and completely ice-free region even in conventional SP SAR approaches (see [14], [27], [29]), consists of about 28% of sea ice. Nonetheless, it is worth noting that sea-ice streaks within the polynya consist of a mixture of sea water and frazil/grease/pancake ice [3] and, therefore, to assume that a single pixel is completely ice-free (i.e., sea water) or ice-covered (i.e., sea ice) is a simplifying but reasonable assumption at the SAR resolution scale.…”

Section: Experiments and Discussionmentioning

confidence: 99%

“…To the best of our knowledge, only few studies addressed the observation of TNB polynya by means of SAR imagery [14], [27], [28], [29]. In all the studies, the polynya boundaries are manually extracted, with the exception of the automatic image processing algorithm based on anisotropic filtering and Markov random fields which is applied to fine-resolution (15 m) X-band SAR scenes under open polynya conditions in [29]. In [14], moderate-resolution (100-150 m) L-and C-band SAR data are used, together with a multisensor satellite dataset, to monitor the polynya variability.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the Terra Nova Bay Polynya Using Dual-Polarimetric C-Band SAR Measurements

Inserra,

Buono,

Nunziata

et al. 2024

IEEE J. Oceanic Eng.

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In polar regions, coastal polynyas are key drivers for climate since they represent the primary source of ice mass production and oceanic circulation. In this study, multipolarization C-band synthetic aperture radar (SAR) measurements acquired by the Radarsat-2 satellite mission are exploited to observe the Terra Nova Bay (TNB) coastal polynya in the Ross Sea, Antarctica. Incoherent and coherent features, extracted from dual-polarimetric SAR measurements, are used to characterize the TNB coastal polynya under different environmental conditions. The analysis is also supported, when available, by independent optical remote sensing information collected by the thermal infrared channels of the moderate resolution imaging spectroradiometer and by ancillary on-site information about wind and air temperature collected by automatic weather stations. Experimental results show that the SAR plays a key role in providing information about the TNB polynya thanks to its fine spatial resolution and its almost continuous imaging capabilities. In addition, dual-polarimetric SAR offers unprecedented opportunities with respect to single-polarization SAR in performing accurate and unsupervised classification of the area within the polynya. Hence, a more accurate estimation of the polynya extent and the fractional area coverage of sea water within the polynyas obtained.

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“…In recent years, some methodological studies presented the use of SAR active microwave systems, mostly operating at C-and X-bands, for the estimation of the TNBP extent e.g., [6,50]. These methods are based on the differences in backscattered radar intensity and image texture which allow the separation of open water, thin ice, and offshore pack ice.…”

Section: Remote Sensing Of the Terra Nova Bay Polynyamentioning

confidence: 99%

A New Approach for Monitoring the Terra Nova Bay Polynya through MODIS Ice Surface Temperature Imagery and Its Validation during 2010 and 2011 Winter Seasons

et al. 2018

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Polynyas are dynamic stretches of open water surrounded by ice. They typically occur in remote regions of the Arctic and Antarctic, thus remote sensing is essential for monitoring their dynamics. On regional scales, daily passive microwave radiometers provide useful information about their extent because of their independence from cloud coverage and daylight; nonetheless, their coarse resolution often does not allow an accurate discrimination between sea ice and open water. Despite its sensitivity to the presence of clouds, thermal infrared (TIR) Moderate Resolution Imaging Spectroradiometer (MODIS) provides higher-resolution information (typically 1 km) at large swath widths, several times per day, proving to be useful for the retrieval of the size of polynyas. In this study, we deal with Aqua satellite MODIS observations of a frequently occurring coastal polynya in the Terra Nova Bay (TNB), Ross Sea (Antarctica). The potential of a new methodology for estimating the variability of this polynya through MODIS TIR during the 2010 and 2011 freezing season (April to October) is presented and discussed. The polynya is observed in more than 1600 radiance scenes, after a preliminary filter evaluates and discards cloudy and fog-contaminated scenes. This reduces the useful MODIS swaths to about 50% of the available acquisitions, but a revisit time of less than 24 h is kept for about 90% of the study period. As expected, results show a high interannual variability with an opening/closing fluctuation clearly depending on the regime of the katabatic winds recorded by the automatic weather stations Rita and Eneide along the TNB coast. Retrievals are also validated through a comparison with a set of 196 co-located high-resolution ENVISAT ASAR images. Although our estimations slightly underestimate the ASAR derived extents, a good agreement is found, the linear correlation reaching 0.75 and the average relative error being about 6%. Finally, a sensitivity test on the applied thermal thresholds supports the effectiveness of our setting.

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Automatic Measurement of Polynya Area by Anisotropic Filtering and Markov Random Fields

Cited by 10 publications

References 26 publications

Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images

Ice Production in Ross Ice Shelf Polynyas during 2017–2018 from Sentinel–1 SAR Images

Characterization of the Terra Nova Bay Polynya Using Dual-Polarimetric C-Band SAR Measurements

A New Approach for Monitoring the Terra Nova Bay Polynya through MODIS Ice Surface Temperature Imagery and Its Validation during 2010 and 2011 Winter Seasons

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