Fast‐ice distribution in East Antarctica during 1997 and 1999 determined using RADARSAT data

Abstract

We present the first detailed maps of fast ice around East Antarctica (75°E–170°E), using an image correlation technique applied to RADARSAT ScanSAR images from November in 1997 and 1999. This method is based upon searching for, and distinguishing, correlated regions of the ice‐covered ocean which remain stationary, in contrast to adjacent moving pack ice. Within the overlapping longitudinal range of ∼86°E–150.6°E, the total fast‐ice area is 141,450 km2 in 1997 and 152,216 km2 in 1999. Calibrated radar backscatter data are also used to determine the distribution of two fast‐ice classes based on their surface roughness characteristics. These are “smooth” fast ice (−25.4 dB to −13.5 dB) and “rough” fast ice (−13.5 dB to −2.5 dB). The former comprises ∼67% of the total area, with rough fast ice making up the remaining ∼33%. An estimate is made of fast‐ice volume, on the basis of fast‐ice type as a proxy measure of ice thickness and area. Results suggest that although fast ice forms 2–16% of the total November sea ice area for this sector of East Antarctica in 1997 and 1999 (average 8.3% across maps), it may comprise 6–57% of the total ice volume (average ∼28% across maps). Grounded icebergs play a key role in fast‐ice distribution in all regions apart from 150°E–170°E. These are “snapshot” estimates only, and more work is required to determine longer‐term spatiotemporal variability.

Fast ice distribution in Adélie Land, East Antarctica: interannual variability and implications for emperor penguins Aptenodytes forsteri

“…from the Radarsat-1 ScanSAR (spatial resolution 100 m over a 500 km swath) obtained from the Alaska Satellite Facility. The latter were derived from a 'snapshot' study of East Antarctic fast ice by Giles et al (2008) using 4 SAR images averaged over the period 2 to 18 November 1997. This gave an areal extent of ~24 700 km 2 .…”

“…Yamanouchi & Seko (1992), Murphy et al (1995), Enomoto et al (2002), Heil (2006), Ushio (2006). Wider-scale studies were carried out by Kozlovsky et al (1977, cited in Fedotov et al 1998, and Giles et al (2008), but are limited in their temporal coverage and do not reveal the frequency and extent of break-up and formation episodes.…”

“…A key feature of fast ice is its recurrence and persistence in certain locations. It forms a highly compact ice cover that can be either annual or perennial, the latter occurring in more sheltered loca-tions (Giles et al 2008). Ephemeral breakouts do occur during storms (Heil 2006), while break-up by oceanswell penetration becomes a factor later in the season when the protective surrounding pack ice has dispersed (Crocker & Wadhams 1989, Langhorne et al 2001, Ushio 2006.…”

“…Responding rapidly to atmospheric and oceanic forcing, it is a sensitive indicator of climate change and/or variability (Murphy et al 1995, Heil 2006. As it can attain a considerable thickness (> 5 m for perennial fast ice, Massom et al 2001), it likely comprises a substantial proportion of the total Antarctic sea ice volume (Giles et al 2008) and forms an important component of the ocean freshwater budget. Moreover, fast ice is of critical ecological importance as a key habitat for microorganisms (Garrison 1991), a region of enhanced primary productivity (Satoh & Watanabe 1988, Arrigo et al 1993, McMinn et al 2000 and a breeding platform for Weddell seals Leptonychotes weddelli (Thomas & DeMaster 1983) and emperor penguins (Kirkwood & Robertson 1997a, Kooyman & Burns 1999.…”

Analysis of Annual Variability of Landfast Sea Ice near Jangbogo Antarctic Station Using InSAR Coherence Images

“…이러한 해빙이 전 지구적 기후 및 환경에 미치는 영향은 상당하다 (Allison et al, 1993). 특히 해안에 고착되어 있는 정착해 빙(landfast sea ice, LFI)은 고위도 지방에서 대기와 해양 사이의 열 전달 작용을 방해하여 국지적 기후변화를 야 기할 수 있으며, 다양한 해양 생물 종의 서식지 형성에 도 큰 영향을 미치고 있다 (Giles et al, 2008). Sensing, Vol.31, No.6, 2015 -5 02 - 특성 분석에 매우 유용하게 활용될 수 있다 (Dammert et al, 1998;Massonnet and Feigl, 1998;Han and Lee, 2011 (Leberl et al, 1983;Leppäranta et al, 1998;Nystuen et al, 1992).…”