After six years of ORCHESTRA and ENCORE research, and with ENCORE having officially ended on the 31st March, what have been the highlights and what foundations have been laid for future research from these projects? Andrew Meijers, who led the projects explains:
“ORCHESTRA (Ocean Regulation of Climate by Heat and Carbon Sequestration and Transports) and its extension project ENCORE was a six year, ~11 million pound BAS led programme involving seven UK research centres. It sought to radically improve our ability to measure, understand and predict the circulation of the Southern Ocean through a series of milestone observational campaigns in combination with model development and analysis. Eleven cruises in the Weddell Sea and South Atlantic were undertaken, along with moorings, glider and profiler process studies and air-sea heat and carbon flux measurements from ships and aircraft. Numerous forward and adjoint model experiments, looking at ocean heat content sensitivities, were developed and supported by extensive analysis of coupled climate models and support for model development at the UK Met Office.
ORCHESTRA/ENCORE has resulted in almost 100 peer reviewed publications so far, innumerable talks and presentations, delivered public outreach and education and supported dozens of postdoctoral and PhD students. As a National Capability programme its voyages, datasets and model development have provided a platform for the wider community to exploit. It directly supported high impact policy relevant documents such as the IPCC Special Report on Oceans and Cryospheres, but also had impact beyond purely physical oceanography. A great example of this were several high impact ecosystems papers supported by ORCHESTRA data, as well as explicit participation in the CCAMLR-ICED workshops and reports.
There have been many research highlights coming out of ORCHESTRA, as well as the development of important community data tools; notably new mappings of hydrographic data and bulk formula code development by NOC partners. Just a few examples of these highlights include:
- Filling in huge gaps in air-sea flux observations through the installation of PML underway heat and carbon flux instrumentation on the RRS James Clark Ross (and soon on the RRS Sir David Attenborough too), and coordinating ship observations with complimentary BAS MASIN flights. Novel results are already emerging showing the impacts that biological surfactants have in suppressing CO2 gas exchange between the ocean and atmosphere.
- The discovery of declining trends in Weddell Sea Bottom Water volumes and export to the Scotia Sea, linked to changes in winds reducing formation rates in front of the Filchner-Ronne Ice Shelf.
- Observational and modelling efforts revealing new patterns in SubAntarctic Mode Water formation sites, and the discovery of strongly varying interannual ‘dipoles’ in formation in the Pacific and Indian basins, with potentially significant impact on our understanding of how the ocean responds to local and remote atmospheric changes and how heat and carbon are sequestered.
- Significant advances in understanding of how problematic Southern Ocean sea surface temperature biases in IPCC coupled climate models are formed (notably due to short wave radiation biases), and supporting the UK Met Office Southern Ocean group in addressing these issues in the HadGEM.
- The completion of a milestone set of hydrographic sections, closing off the Weddell Sea and South Atlantic in two ‘boxes’, allowing the estimation of heat and carbon flux, storage and transports into and out of these key regions.
While it is now formally finished, ORCHESTRA and ENCORE will continue to produce results and significantly influence the Southern Ocean communities thinking for many years to come. It has been a great privilege and pleasure to lead this programme with such a motivated and talented group of scientists.