Introduction and Background
Satellite Earth observation has revolutionized our understanding of the remote and inaccessible Polar Regions. Without this critical resource we would have a far less complete understanding of which regions are changing, the timing and pace at which events occur, and what physical mechanisms are responsible for driving change. In Antarctica, satellite data has been vital for revealing the continent-wide spatial pattern of ice flow; for uncovering dynamic imbalance and the associated large sea level contribution of the marine-based West Antarctic Ice Sheet; for mapping the seasonal growth and decay of sea ice extent; and for measuring the size and recovery of the Ozone hole. These major advances are noteworthy, but are just a fraction of the key findings that would not have been made without the availability of satellite data. This highlights what an essential tool Earth observation is for improving our understanding of environmental change in Antarctica, and why it is so important to continue to acquire high-quality satellite data-sets. The SCAR Earth Observation Action Group (EOAG) is new effort aimed at advising spacefaring nations on Antarctic and Southern Ocean region (up to 60° S) data acquisitions, and supporting the preservation of past data for long-term analysis.
The purpose of the SCAR Earth Observation Action Group (EOAG) is primarily to:
- be a permanent advocate for acquiring all types of satellite data over the Antarctic and Polar regions from multiple space agencies, as was successfully done in the International Polar Year (IPY);
- to make recommendations about the type and accuracy of satellite observations required in order to measure Essential Climate Variables (ECV’s) relevant to the Polar regions;
- identify a programme of grand science challenges which can best be tackled with Earth Observation data;
- advocate for and make recommendations about how best to preserve the long term continuity of satellite Earth Observation data records.
Among the data sets needed are ice flow speed, ice thickness change, sea ice extent and concentration, surface mass balance, and ocean and snow surface temperatures. These observations are critical for long-term monitoring and understanding changes in these variables which may be caused by short term weather events, or longer term climate change. High quality datasets now extend over the last three decades, and are increasingly large in data volume, making data storage and analysis cumbersome and expensive to safely store. However, the detailed and well-described preservation of satellite measurements offer irreplaceable insights into the historical environmental conditions and their progression through time. EOAG recommendations will be of value to the scientific community who are the primary user of satellite datasets in Antarctica, and to international organizations such as space agencies, who require community-coordinated recommendations about data requirements both now and in the future.
Motivation
The motivation for setting up a SCAR Earth Observation Action Group (EOAG) is threefold. Firstly, we now have over 30 years of science-quality, multi-technique, satellite observations of Antarctica which are held in space agencies globally. Although there’s a clear move towards a free and open data policy in the US and Europe for newly acquired satellite data, preserving long-term data archives of historical data still requires funding, even though it’s not necessarily the new and exciting topic. This is not trivial when you consider for historical missions like ERS-1, active in the early 1990’s, this has already involved migrating the data archive from tapes, to CD’s to online archives. There are now examples of published datasets that have been lost during the moves. As historical observations are critical for disentangling short term temporary variability from long term permanent change, it is essential that international organizations like SCAR, advocate for continued preservation of these archives.
Secondly, currently flying satellite missions, such as Sentinel-1, acquire data with incomplete geographical and temporal coverage. When designing acquisition plans, the space agencies require guidance from the scientific community about where to prioritise in the acquisition plan. For SAR data over land ice, groups such as the Polar Space Task Group consult interested members of the community, but again a long-term, considered plan from a full, multidisciplinary community would be a really valuable input that SCAR can coordinate.
Finally, when existing satellite missions will come to the end of their life without a follow-on satellite mission secured, recommendations from SCAR about the value of securing future data continuity would be extremely valuable. Despite a constant increase in the number and type of active Earth observation missions, the danger of an observational gap for measuring essential parameters still exists. For example, there is a danger we will lose our ability to measure sea ice extent and thickness over oceans without new passive microwave radiometer and high latitude altimeters being procured; and there will be a reduction in the spatial resolution with which we can monitor ice sheet elevation change on the most rapidly thinning ice sheet margins unless a new synthetic aperture radar interferometer mode altimeter is funded. As an independent and community driven organization, recommendations from SCAR may be used to influence these major decisions over the coming 5 to 10 years.
Objectives
The EOAG will:
- Be a permanent advocate for acquiring all types of satellite data over the Antarctic and Southern Ocean region (up to 60° S).
- Make recommendations about the type and accuracy of satellite observations required in order to measure Essential Climate Variables (ECV’s) relevant to the Polar Regions.
- Identify a program of grand science challenges which can best be tackled with Earth Observation data.
- Advocate for the preservation and continuity of long term satellite Earth Observation data records.
Complimenting Existing SCAR Activities
The EOAG will overlap and support the work of existing activities within SCAR that make use of, but are not solely focused on, using satellite data. For example, while ANTOS looks to secure observations in the near-shore zone, or the Remote Sensing of Birds and Animals group looks to make observations on biologically relevant spatial and temporal scales, there is an important role for focusing on glaciological, oceanographic and other environmental parameters that are continent-wide and not solely linked to Antarctic ecosystems. While satellite observations are one component of SOOS, again they are not the focus, therefore there is a significant enough gap that a standalone Earth observation action group would add value to SCAR. The Earth Observation action group will directly engage with space agencies globally, and engage with the scientific community working with both raw satellite data and higher level geophysical processed products to ensure science priorities are identified and supplied with the satellite data required to support them.
In 2021, the Remote Sensing group merged with the Earth Observation group.
