Components of an Antarctic and Southern Ocean Observing System
The committee has described the motivation for an Antarctic observing network with data integration and advanced scientific modeling in Section 4.4. This appendix further describes examples of several of the important observations that would be of greatest use in such a network providing information on the atmosphere, ocean, ice, and biology and biogeochemistry. The list is neither meant to be comprehensive, nor should the following be seen as a description of the final design of an Antarctic and Southern Ocean observing system. Detailing a comprehensive strategy for such an observing system was believed beyond the scope of this committee; any such strategy would be best done by an independently selected committee of specialists, especially with respect to cyberinfrastructure requirements that might need long lead times for development and deployment. For example, the development of the Arctic Observing Network required several steps from stating the need, to the recommendation, and finally to defining optimum design and implementation strategies. Such a process in other regions has required the engagement of several efforts by specially selected committees and working groups and has been documented in multiple reports over a period of a decade. Building on the experience of other observing system design efforts and using the work already invested into components of an Antarctic and Southern Ocean observing system could shorten the time needed for implementation of such a network.
ATMOSPHERE
For atmospheric observation, it is important to create a network that measures and reports a wide range of variables and can withstand the severe Antarctic environment. The Antarctic automatic weather station network started as a U.S. program in 1980 with only a few stations. It has expanded to more than 100 locations across Antarctica from 12 different nations.1 Initially basic near-surface meteorological variables were measured, but the range of parameters monitored and topics tackled continues to
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grow. Applications of the data include investigations of specific atmospheric phenomena (like katabatic winds), climate monitoring, critical input for numerical weather prediction, and ground-based weather for aircraft landings. The network should be a core component for an Antarctic observing network.
Redundant, autonomous mobile sensors controlled by adaptive networks are well worth exploring for the Antarctic continent, while enhanced drifting buoys might be used in the sea ice zone and open ocean regions. Ground-based remote sensing involving radar, wind profilers, Doppler acoustic sounders, temperature profilers, cloud radars, and cloud LIDAR can improve upon data retrieved from current radiosondes. In addition, large numbers of simple dropsondes strategically released from high-altitude balloons could enhance data collection. Research aircraft are appropriate platforms for investigating atmospheric processes (e.g., cloud physics). In addition, it would be desirable to replace expensive, bulky, sensitive instrumentation maintained by expert technicians with simpler, more capable systems that can work in unmanned aircraft to routinely explore the behavior of the winds, temperature, moisture, and cloud fields in three dimensions.
Satellites over the Antarctic continent and Southern Ocean have great promise: radio occultation profiles from tracking the propagation of GPS signals through the atmosphere have proved useful over the Antarctic continent with all-weather capability and absolute calibration. Long-range planning for satellites is required. NASA’s Earth Observing System (the Terra and Aqua satellites) and the more recent Cloudsat and CALIPSO missions have proven their value to science, but there are no adequate follow-up plans for when these systems exceed their design lifetimes. Data obtained on the atmosphere must be integrated into a coherent framework to support modeling.
OCEAN
Ocean observations can use both Eulerian (moored) and Lagrangian (moving) platforms. Eulerian measurements performed at strategically chosen locations, such as within straits, choke points, and boundary currents, would prove valuable. Improved moored sensors capable of conductivity-temperature-depth oxygen, nitrate, fluorescence, and acoustics and of flow cytometry of colored dissolved organic matter will be helpful. Devices with passive sonic recording of whales would improve the tracking of whales. Near-surface ocean platforms are in danger of damage from icebergs. Alternative sampling strategies including instrumented animals (seabirds, seals, whales), gliders, and autonomous underwater vehicles (AUVs) can mitigate this problem.
Lagrangian measurements can take place from a number of platforms, including profiling floats (e.g., Argo floats), gliders, and AUVs. Important oceanography measurements include currents, temperature, oxygen (O2), CO2, pH, turbidity, and nutrient levels. There is a critical lack of observations beneath floating ice shelves.
ICE
Observations of both glacial and sea ice are crucially lacking. Among the many measurements needed for glacial ice are three-dimensional englacial temperatures, basal conditions (e.g., frozen versus thawed bed, sediment at bed, subglacial lakes), geothermal heat flux, physical properties of ice (density, grain size, fabric), grounding line mapping, and ice thickness. A comprehensive measurement scheme will require many boreholes, cores (some continuous and others not), new drilling technologies, and new tools for englacial measurement. Airborne methods to measure ice thickness have already shown promise, but further work is required. Among other important variables to measure are accumulation rates, glacial surface temperatures, ice velocity, ice thickness, surface elevation, changes in grounding lines, and location of subglacial lakes. Acoustic depth gauges, surface density measurements, near-surface temperature profiles, and other strategies may provide valuable information for an observing network.
Sea ice observing will rely heavily on satellite measurements (ice extent, thickness for mass balance), drifting buoys (ice motion and ice mass balance), and in situ sampling (physical, chemical, and biological sea ice properties). Upward-looking sonars on AUVs can reliably measure sea ice thickness.
BIOLOGY AND BIOGEOCHEMISTRY
Answering a number of biology and biogeochemistry research questions on both land and ocean can benefit greatly from a network of observations. In the ocean, important observations include ocean-air DPCO2; continuous flow, underway O2-Argon and D17O from vessels; cabled observatories near coastal stations; and ocean color measurements from satellites (Behrenfeld et al., 2006), e.g., Wide Field-of-view Sensor (SeaWiFS)/Moderate Resolution Imaging Spectroradiometer (MODIS) (McClain, 2009). A recent NRC review of this situation concluded that the current ocean color time series from satellites is at risk and that NOAA and NASA should be encouraged to establish a working group modeled after the International Ocean Colour Coordinating Group
(IOCCG) to work toward a sustained ocean color data collection program from U.S. and non-U.S. sensors (National Research Council, 2011a).
On land, light detection and ranging (LIDAR) can be used to study permafrost at local scales, and monitoring stations could include microclimate information on soil temperature, water activity, carbon dioxide (CO2), and pulsed amplitude modulation fluorometry. In freshwater, an observing network would benefit from in situ sensors to measure carbon, nitrogen, phosphorus, and stable isotopes of hydrogen, oxygen, and nitrogen, as well as dissolved CO2 sensors and dissolved oxygen sensors. An oxygen (O2) flux tower would provide important information. Inclusion of data from a network of terrestrial, aquatic, and glacial monitors could help define predictions of rates of land transformation and the resulting atmospheric and hydrologic feedbacks; these are important processes to follow as glaciers and permafrost melt, lakes overflow, or land is exposed.
