As we reminded the larger community in our CWP ( http://www.oceanobs09.net/blog/?p=71 ) the OceanObs’99 conference accepted tomography as a component of the ocean observing system, highlighting the regions of the North Atlantic and the Arctic for implementation. The OceanObs’09 conference statement reiterates the OceanObs’99 plan, hence it reiterates the acceptance of tomography for implementation in the North Atlantic and Arctic. This acceptance is consistent with the consensus view of tomography during OceanObs’09. Two of the plenary talks highlighted the roles of tomography in the ocean observing system, particularly mentioning the averaging capability of this line-integrating measurement type and the capability to “remotely sense” the abyssal ocean. The averaging was seen as particularly important in such areas as the North Atlantic where the deep ocean is highly variable, so measurements by, e.g., sparse, infrequent deep hydrographic profiles are minimally effective.
There were several plenary speakers who expressed the opinion that no data type was redundant, and indeed this sentiment is reflected in the Summary. One important aspect of the observing system that was not mentioned during the conference was the occasional systemic failures of elements of the system, e.g., the pressure bias of Argo floats, (since corrected), errors in XBT fall rates, or the problems that arose during the T/P satellite change over. Such problems will occur from time-to-time, hence, as outlined in our CWP, it is important to build more complementary, independent measurements into the observing system. A certain amount of “redundancy” is essential to achieve a robust system. In addition to its unique capabilities, tomography contributes to such redundancy.
We feel it is particular important to highlight tomography in this Summary to ensure that tomographic methods are accurately presented in the Summary. Indeed, acoustical oceanography broadly, as a subject in its own right on par with biogeochemical oceanography, as a tool used for ocean observation, and as an engineering tool for such things as communications and navigation, must be a key component of any ocean observing system. The Summary should reflect the important potential of acoustics for ocean observing in the coming decade, as presented in many of the talks and papers at OceanObs’09.
1. Pages 4-5, Session 2A: Large-scale ocean properties: science, observations, and impacts
“Though ice covered regions pose a serious challenge to surface and subsurface data collection, recent technological developments now allow under ice measurements over extended regions for the first time. There is evidence of deep ocean (below 2000m) warming and salinity changes which have significantly impact our understanding of the planetary energy budget and long term sea level changes, but current sampling is inadequate.”
Please follow this with:
“Integrated acoustic systems for navigation, communications, and tomography coupled with mobile sampling platforms is one technological solution to these challenges, in particular for the ice infested oceans. Such systems are currently under development for example in the Fram strait”
“- Key gaps are the ice-covered regions and the deep oceans. The latter requires further technological developments and system design.”
Please modify to:
- Key gaps are the ice-covered regions and the deep oceans. Implementation and continuing development of appropriate mobile platforms and integrated acoustics systems for navigation, communication and tomography are appropriate.
2. Page 5, Session 2B: Large-scale ocean circulation and fluxes
In Paragraph 2 ” … it requires the combination of various measurements, including repeat hydrography, ARGO profiles, boundary current moorings and acoustic techniques … ”
Please append: … “such as acoustic tracking or navigation and acoustic tomography.”
“Argo profiling has proven to be an excellent, tantalizing tool for studying ventilation.”
We remind the Conference that tomography was employed in the late ’80’s to study deep convection in the Greenland and
Mediterranean Seas, particularly demonstrating the value of integral measurements in measuring and quantifying the amount
of deep water formation. See the OceanObs’99 review paper “Observing the ocean in the 2000’s: A strategy for the role of acoustic tomography in ocean climate observation.”
“At latitudes other than 26°N, horizontal gyres contribute to meridional heat flux. This poses serious technical challenges, although PIES can in some cases be used with proxy techniques to resolve the temperature field in the ocean interior.”
Change to: “At latitudes other than 26°N, horizontal gyres contribute to meridional heat flux. The measurement of meridional heat flux in the presence of horizontal gyres poses serious technical challenges. The use of acoustic tomography combined with CPIES (in regions with shorter scales) can be used to resolve the temperature and velocity field in the ocean interior.”
3. Page 11 3E: Community Forum: World Climate Research Program: Towards integrated ocean basin observations planning
“In the Pacific Ocean, to be complemented by an upcoming OKMC, NPOCE has been running for some 15-years with a focus on the interaction between western boundary currents (WBCs) the tropical Pacific warm pool.”
In the Pacific Ocean, the recently completed decade-long Acoustic Thermometry of Ocean Climate (ATOC) project demonstrated the ability to collect high signal-to-noise, basin scale path averaged heat content data with high temporal resolution (days). The Northwest Pacific Ocean Circulation and Climate Experiment (NPOCE) has been running for some 15-years with a focus on the interaction between western boundary currents (WBCs) the tropical Pacific warm pool. NPOCE will be complemented by an upcoming Philippine Sea tomography experiment and the Origins of Kuroshio and Mindanao Current (OKMC) project.
4. Page 13, Session 4A: In situ ocean observation
In Paragraph 1:
“The past decade has seen rapid development of systematic and innovative in situ ocean observing systems using both mobile and fixed-point platforms. These include research Ships, Volunteer Observing Ships (VOS), drifters, gliders, animals with sensors, moorings, cables, landers, AUVs and ROVs. These advances are set to revolutionize our understanding and monitoring capabilities of the global ocean, particularly for complex biological and biogeochemical variables and processes. For the first time we are addressing the reality of simultaneous multidisciplinary, multi-scale ocean observations with real-time open data access through technology e.g. telemetry and marine cables enabling intelligent, interactive sampling.”
Please re-phrase as follows:
The past decade has seen rapid development of systematic and innovative in situ ocean observing system sensor network infrastructure elements. These elements include both mobile and fixed-point platforms (e.g., research Ships, Volunteer Observing Ships (VOS), drifters, gliders, acoustic thermometry, animals with sensors, moorings, cables, landers, AUVs and ROVs) and the associated power, communications, timing, and navigation subsystems (e.g., wind/solar/fuel cell/wave energy for surface moorings, and integrated acoustics).
These advances are set to revolutionize our understanding and monitoring capabilities of the global ocean, particularly for complex biological and biogeochemical variables and processes. For the first time we are addressing the reality of simultaneous multidisciplinary, multi-scale ocean observations with real-time open data access through technology e.g. telemetry and marine cables enabling intelligent, interactive sampling.”
5. Page 15, Section 4C: Information Synthesis and Delivery
“The existing GOOS must be maintained and extended to include full-depth Argo-type measurements, and enhance information about boundary currents, transports through key regions, and in marginal seas.
Please delete: “to include full-depth Argo-type measurements”
This recommendation is listed already on page 9, and in singling out a specific measurement type, the phrase is inconsistent with the general nature of these Recommendations.
6. Pages 16-17 Session 5B: Toward in integrated Observing System.
This is an as yet sparse but important section. One possible paragraph to include here would be:
“Reinforcing recommendations from OceanObs99, implementation of an explicit acoustics component of the observing system is called for to address: improved synoptic basin scale volumetric heat content estimates including the deep ocean and under ice; provision of communications and navigation infrastructure (e. g., basin-wide mobile platform tracking); and monitoring of marine organisms, wind, rain, earthquakes, and anthropogenic (shipping) sound.”
The summary needs to provide more synthesis. It reads now like a compilation of somewhat disjoint sections. The Executive Summary should do some of this, but the current text needs to be harmonized. (I do understand this is the first draft.)
All acronyms must be defined at first use.
There is very little mention of the Arctic.
Along with successes, failures should be noted:
1. Problems with incorrect reporting of pressure on a significant fraction of Argo floats
2. Failure to correctly account for fall rate errors of XBTs
3. Recent failures of a whole batch of Argo pressure sensors.
Results published prior to recognizing 1 and 2, and the subsequent retraction and reanalysis, provided fuel for those subscribing to “no change or cooling”. Further, on one hand there is acclamation that Argo is “complete” yet on the other hand something like 10 - 30 per cent of deployed floats are not functioning correctly (partly as a result of point 3).
Recommendation: Build more complementary, independent measurements into the observing system; a certain amount of “redundancy” is essential to achieve a robust system.
There was little discussion of overall system requirements and metrics. For instance, what are the requirements for measuring heat content as a function of time and space (horizontal and vertical) scales? How close does the current system come to achieving the requirements? What observing system simulation experiments (OSSEs) have and should be run to provide guidance for improving the system to achieve the requirements. The Ocean Observing System is said to be a system of systems, but the system engineering that integrates and glues these systems together is not evident.
Recommendation: Provide a structure for setting requirements, evaluating current capability, and recommending improvements, within a system engineering framework.
There should be a final summary of recommendations, as concrete as possible. This may or may not fit in the Executive Summary, yet to be written.
P5 Session 2B: Large-scale ocean circulation and fluxes
Define EM profiling
P9 3B: Forecasting
“Sustain the current observing systems and complete impending missions — no redundancies are identified in the observing system.”
What is the purpose of the last phrase? Is redundancy a positive or negative system attribute? Per comments above, complementarity (e.g., independent measurement systems) and some redundancy is good. But what is a redundant measurement? One that is within a correlation scale of another? If so, we will never be there. On the other had, if there are two measurements next to each other, that is one but only one check on error, which is good. Are you trying to make the point that money is not being wasted on too many sensors?
P15 Session 4C: Information Synthesis and Delivery
again, the use of the word redundancy.
P16-17 Session 5B: Toward an integrated Observing System
This is one of the most important sections. It should describe in more concrete detail what is being recommended be done in the next 10 years – and longer, especially what new things. These are the things we are saying the sponsors and governments should be allocating funds for.
It may be sparse because drafts of two of the five plenary papers for this section (and some other relevant other plenary papers) had not yet been posted.]]>