Remote Sensing of Near-Coastal Antarctic Sea Ice and Its Impacts on Ice Shelves and Ecosystems.

Metadata record for data from AAS (ASAC) Project 3024.Public The proposed research will derive improved estimates of East Antarctic fast-ice extent and thickness, and their variability, from satellite data. These will be used to explicitly test relationships between fast ice/other environmental parameters and Emperor penguin population dynamics. We shall also combine observations with a wave-ice shelf-sea ice interaction model to test the hypothesis that catastrophic ice shelf break-up events on the E. Antarctic Peninsula are linked to increased ocean wave energy associated with sea-ice extent anomalies (driven by atmospheric anomalies), and/or long-period swell from far-remote storms. This work will aid comprehension of processes responsible for recent rapid ice-shelf demise.Project objectives:1. To measure and monitor East Antarctic fast ice areal extent and thickness, and their spatio-temporal variability, using satellite remote sensing.2) To analyse the impact of fast ice variability on the breeding success of Emperor penguins (Aptenodytes forsteri).3) To investigate the potential impact of sea ice on recent ice shelf break-up breakup on the Antarctic Peninsula.Taken from the 2008-2009 Progress Report:This project has shown a strong correlation between interannual fast ice variability and Emperor penguin breeding success at Dumont d'Urville, and has produced satellite-based maps of East Antarctic fast ice (radar snapshot mosaics from November 1997/98 and 20-day composite images for 2005-2008, extending back to 2000). Secondly, significant progress was made towards implicating an atmospherically-driven anomalous lack of sea ice in recent Antarctic ice-shelf disintegrations. Finally, new research highlights a previously-overlooked mechanical coupling between the floating Mertz Glacier tongue and very thick (greater than 25m) and old (greater than 20yrs) fast ice attached to it, with important implications for ice-sheet margin stability.Taken from the 2009-2010 Progress Report:Progress against objectives:1) To measure and monitor East Antarctic fast ice areal extent and thickness, and their spatio-temporal variability, using satellite remote sensing.Considerable progress has been made against this objective, building on last year's publication of the first detailed "snapshot" maps of landfast sea ice (fast ice) extent around the East Antarctic coast from 75 degrees E-170 degrees E for the Novembers of 1997 and 1999 using RADARSAT satellite ScanSAR images (see Giles et al., 2008). The main achievements are:* The development of an improved semi-automated method to successfully derive fast ice extent (and pack ice motion) from time series of Envisat Advanced SAR images (Giles et al., in prep.), via a project with the European Space Agency and the International Space Science Institute (Berne, Switzerland). Fast ice is identified as regions of zero motion in the cross-correlation analysis of carefully co-registered pairs of satellite SAR images.* Significant progress in the PhD project (Alex Fraser) aimed at deriving longer and near-continuous time series of fast ice extent from time series of NASA MODIS visible and thermal IR imagery at 1 km resolution. A major challenge has been to address the problem of effectively 'removing' persistent cloud cover from the images. This has been achieved by compositing many thousands of MODIS images to create 20-day composite images of the entire East Antarctic coastal zone from 10W to 170E. This technique was showcased at the prestigious International Geoscience and Remote Sensing 2009 conference in South Africa in July 2009 (Fraser et al., 2009a), with subsequent publication by Fraser et al. (2009b). During the year, this work resulted in an important new time series of fast ice extent that runs from 2000 to 2008 inclusive (Fraser et al., in prep.), with techniques being described in Fraser et al. (in press). This unique dataset represents by far the most detailed estimate of East Antarctic fast ice and its spatio-temporal variability to date. It furthermore represents an important new baseline against which to gauge change, given that Antarctic fast ice is a key yet poorly understood component of the global cryosphere (and ocean freshwater budget), is of immense ecological significance (see 2 below), and is a sensitive indicator of climate change/variability. This baseline is directly comparable to the more familiar overall sea ice (pack ice) extent product. Work is underway to determine why large regional differences occur in fast ice distribution and behaviour, including analysis of the role of bathymetry, grounded icebergs and changes in wind patterns. This work also provides crucial regional-scale fast ice information in support of detailed localised fast ice measurements carried out within the Antarctic Fast Ice network at Casey and Davis (AAS 3032).* A collaborative project has been established with Drs Fricker (USA) and Legresy (France) to estimate the thickness of a large region of perennial fast ice adjacent and attached to the Mertz Glacier Tongue. This has been achieved by combining satellite imagery with surface elevation data from the NASA's ICESat laser altimeter satellite, although current unknowns include the thickness and density of the overlying snowcover. The results suggest that this fast ice is extraordinarily thick i.e. greater than 25 m, and may be at least 20 years old (Massom et al., subm., a). Work examining the glaciological significance of this extremely thick fast ice is described in 3 (below). Work is also underway to evaluate the impact on this and regional fast ice of the major calving of the Mertz Glacier in February 2010.2) To analyse the impact of fast ice variability on the breeding success of Emperor penguinsThe first element of this multi-disciplinary, international study was completed last year i.e. a case study showing strong links between Emperor penguin breeding success at Dumont d'Urville and fast ice distribution along the Adelie Land coast of East Antarctica and its variability due to variability in the regional wind field. Results were published in Marine Ecology Progress Series (Massom et al., 2009a), and were also presented in a keynote address to the Xth SCAR International Biology Symposium in September 2009. Work is underway to extend this study both temporally and to other species and regions, using the new MODIS-derived time series of 20-day composite maps of fast ice extent (see 1 above). This work will include a comparison of the fast ice information with new data from French penguin scientists (Drs Barbraud, Ancel and LeMayo) on Emperor penguin mortality and other demographic parameters, with a view to discovering links between the penguin demographics and fast ice variability due to changing weather patterns. Further work is in its initial stages to study the impact of fast ice variability on i) Weddell seal foraging behaviour (with Dr Hindell's group at the Univ. of Tasmania), ii) Adelie penguin breeding success and foraging behaviour (with Drs Southwell and Emmerson, AAD), and iii) other Emperor penguin colonies in East Antarctica (with Dr Wienecke, AAD). Ongoing/future work will also evaluate the impact of abrupt change on the seals and penguins at Dumont d'Urville following the Mertz Glacier calving in February 2010.

本元数据记录源自AAS（ASAC）项目3024（Public）。本研究计划基于卫星数据，改进东南极固定冰（fast ice）的范围与厚度及其变化特征的估算精度，以此明确检验固定冰与其他环境参数之间的关联，以及帝企鹅（Aptenodytes forsteri）种群动态。此外，本研究还将结合观测数据与浪-冰架（ice shelf）-海冰（sea ice）相互作用模型，验证下述假说：南极半岛东部的灾难性冰架崩解事件，与由大气异常引发的海冰范围异常所伴随的海浪能量增强，以及/或者源自遥远风暴的长周期涌浪存在关联。本研究将有助于解析近期冰架快速消亡的相关过程。

项目目标：
1. 利用卫星遥感技术，测量并监测东南极固定冰的面积范围与厚度，及其时空变化特征。
2. 分析固定冰变化对帝企鹅（Aptenodytes forsteri）繁殖成功率的影响。
3. 探究海冰对南极半岛近期冰架崩解事件的潜在影响。

摘自2008-2009年度进展报告：
本项目已发现，迪蒙·迪维尔站（Dumont d'Urville）的年际固定冰变化与帝企鹅繁殖成功率之间存在显著相关性；同时生成了东南极固定冰的卫星制图成果，包括1997/98年11月的雷达快照镶嵌图，以及2000年起、覆盖2005-2008年的20天合成影像。其次，本项目在证实「大气异常驱动的海冰异常偏少」与近期南极冰架崩解之间的关联方面取得了重要进展。最后，最新研究揭示了此前被忽视的漂浮默茨冰川舌（Mertz Glacier tongue）与其附着的超厚（厚度大于25米）、高龄（存在时长超过20年）固定冰之间的机械耦合作用，这一发现对冰盖边缘稳定性具有重要意义。

摘自2009-2010年度进展报告：
目标完成进展：
1. 利用卫星遥感技术，测量并监测东南极固定冰的面积范围与厚度，及其时空变化特征。
本项目在去年研究成果的基础上取得了显著进展：此前团队基于RADARSAT卫星ScanSAR影像，绘制了1997年和1999年11月、东经75°至170°范围内东南极沿岸的首套详细固定冰「快照」分布图（详见Giles等人2008年研究）。主要成果包括：
* 开发了改进的半自动方法，通过对经过精确配准的卫星合成孔径雷达（SAR）图像对进行互相关分析，将零运动区域识别为固定冰，成功从Envisat先进SAR影像的时间序列中提取固定冰范围（以及浮冰群（pack ice）运动）（Giles等人，待发表）；该研究与欧洲空间局及国际空间科学研究所（瑞士伯尔尼）合作完成。
* 博士生Alex Fraser的研究取得重要进展，该研究旨在基于NASA中分辨率成像光谱仪（MODIS）1公里分辨率可见光与热红外影像的时间序列，获取更长时间跨度、近乎连续的固定冰范围时间序列。当前的主要挑战是有效去除影像中的持续云覆盖，团队通过合成数千幅MODIS影像，生成了西经10°至东经170°范围内整个东南极沿岸区域的20天合成影像，该技术于2009年7月在南非举办的国际地球科学与遥感大会2009（IGARSS 2009）上展示（Fraser等人，2009a），后续研究成果于Fraser等人2009b发表。本年度，该工作生成了覆盖2000年至2008年（含首尾年份）的全新固定冰范围时间序列（Fraser等人，待发表），相关技术细节见于Fraser等人（印刷中）。这套独特的数据集是目前为止对东南极固定冰及其时空变化特征最详尽的估算成果；同时，鉴于南极固定冰是全球冰冻圈以及海洋淡水收支中关键但认知匮乏的组成部分，具有极高的生态重要性（详见目标2），且是气候变化/变异的敏感指示器，该数据集为评估变化提供了重要的新基准，且可与更为人熟知的整体海冰（浮冰群）范围产品直接对比。当前研究正在解析固定冰分布与行为存在显著区域差异的原因，包括分析水深、搁浅冰山以及风场变化的作用。本研究还为凯西站（Casey）与戴维斯站（Davis）的南极固定冰网络（AAS 3032）中开展的精细化局地固定冰测量提供了关键的区域尺度固定冰信息。
* 与美国Fricker博士及法国Legresy博士合作开展了一项研究，旨在估算毗邻并附着于默茨冰川舌的大片常年固定冰的厚度。研究通过结合卫星影像与NASA冰、云、陆地高度卫星（ICESat）激光测高卫星的地表高程数据实现了这一目标，但当前仍存在未知因素，包括上覆积雪的厚度与密度。研究结果表明，该固定冰厚度极厚——超过25米，且存在时长至少可达20年（Massom等人，已投稿a）。关于该超厚固定冰的冰川学意义的研究详见目标3。当前研究还在评估2010年2月默茨冰川大规模崩解对该区域及周边固定冰的影响。

2. 分析固定冰变化对帝企鹅繁殖成功率的影响
这项多学科国际研究的第一项内容已于去年完成：案例研究显示，迪蒙·迪维尔站的帝企鹅繁殖成功率与东南极阿德利地沿岸的固定冰分布及其因区域风场变化引发的波动之间存在紧密关联。研究成果发表于"Marine Ecology Progress Series"（Massom等人，2009a），并于2009年9月在第十届南极研究科学委员会（SCAR）国际生物学研讨会上作为主题报告展示。当前研究正基于前述由MODIS生成的20天固定冰范围合成影像时间序列，将该研究在时间维度上进行拓展，并覆盖其他物种与区域。该研究将把固定冰信息与法国企鹅研究团队（Barbraud博士、Ancel博士与LeMayo博士）提供的帝企鹅死亡率及其他种群参数的新数据进行对比，以期揭示天气模式变化引发的固定冰波动与企鹅种群动态之间的关联。此外，初步研究正在开展，旨在探究固定冰变化对以下对象的影响：i) 威德尔海豹的觅食行为（与塔斯马尼亚大学Hindell博士团队合作）；ii) 阿德利企鹅的繁殖成功率与觅食行为（与澳大利亚南极局（AAD）的Southwell博士及Emmerson博士合作）；iii) 东南极的其他帝企鹅聚居地（与澳大利亚南极局的Wienecke博士合作）。后续/未来研究还将评估2010年2月默茨冰川崩解后，迪蒙·迪维尔站的海豹与企鹅所受到的突发变化影响。