For those in the UK who want the latest information about the Southern Ocean you might want to attend the following up-coming session of The Royal Society:New models and observations of the Southern Ocean, its role in global climate and the carbon cycle
9:00 am on Tuesday 16 July 2013 – 5:00 pm on Wednesday 17 July 2013
at The Royal Society at Chicheley Hall, home of the Kavli Royal Society International Centre, Buckinghamshirehttp://royalsociety.org/events/2013/southern-ocean-models/
The Southern Ocean is the most remote and the least understood of the world’s oceans, but plays a crucial role in past and present climate change. Currently it is the focus of intense physical and biogeochemical research. This meeting will bring together observationalists and modellers to exchange their latest insights, and will reach across the disciplines to bring together physical oceanographers, climatologists and carbon cycle scientists.
Session 1: The Southern Ocean: large-scale circulation and climate
Dr Stephen Rintoul, CSIRO and Antarctic Climate and Ecosystems Cooperative Research Centre, AustraliaSouthern Ocean circulation, variability and links to climate
Dr Stephen Rintoul, CSIRO and Antarctic Climate and Ecosystems Cooperative Research Centre, Australia
Dr Sarah Gille, University of California San Diego, USAPoleward heat transport in the Southern Ocean: identifying roles of winds and fronts
Dr Sarah Gille, University of California San Diego, USA
Professor Mike Meredith, British Antarctic Survey, UKDense water export in the Atlantic sector of the Southern Ocean: mechanisms, changes and consequences
Professor Mike Meredith, British Antarctic Survey, UK
Dr Kevin Speer, FSU, USAFloat observations of the Southern Ocean: insights and implications
Dr Kevin Speer, FSU, USA
Professor Karen J Heywood, University of East Anglia, UKProcesses at the Antarctic continental slope important for climate and the carbon cycle
Professor Karen J Heywood, University of East Anglia, UK
AbstractAcceleration of Antarctic ice sheet loss is mainly driven by basal ice shelf melt, in turn determined by ocean-ice interaction and related to the heat transport onto the Antarctic continental shelf. Processes of water mass transformation through sea-ice formation/melting and ocean-atmosphere interaction on the Antarctic continental shelf are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models however cannot include such small-scale processes and struggle to reproduce the water mass properties of the region.
Changes in temperature and salinity of Southern Ocean water masses have been identified regionally. Here we discuss recent changes in water mass properties on the Antarctic continental shelf. Some of the mechanisms through which the warm waters offshore in the Southern Ocean may penetrate onshore are discussed, including eddies and along-slope waves.
In early 2012 the GENTOO project deployed three Seagliders for up to two months to sample the water to the east of the Antarctic Peninsula in unprecedented temporal and spatial detail. We discuss evidence in the Seaglider data of exchanges across the shelf-break front (the Antarctic Slope Front), including observations of dense water spilling off the continental shelf, and of a subsurface lens of Warm Deep Water on the shelf emanating from offshore. GENTOO demonstrated the capability of ocean gliders to play a key role in a future Southern Ocean Observing System.
Session 2: Southern Ocean mixing and controls on circulation
Dr James R Ledwell, Woods Hole Oceanographic Institution, USADiapycnal mixing from coordinated tracer and turbulence measurements
Dr James R Ledwell, Woods Hole Oceanographic Institution, USA
Professor Raffaele Ferrari, MIT, USARecent observations of Southern Ocean mixing and their implications
Professor Raffaele Ferrari, MIT, USA
AbstractThe Meridional Overturning Circulation (MOC) of the ocean is a critical regulator of the Earth's climate processes. Climate models have been shown to be highly sensitive to the representation of lateral eddy mixing in the southern limb of the MOC, within the Antarctic Circumpolar Current latitudes, although the lack of extensive in situ observations of Southern Ocean mixing processes has made evaluation of mixing somewhat difficult. We present the first direct estimate of the rate of lateral eddy mixing across the Antarctic Circumpolar Current is presented. The estimate is computed from the spreading of a tracer released upstream of Drake Passage as part of the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES). The meridional eddy diffusivity, a measure of the rate at which the area of the tracer spreads along an isopycnal across the Antarctic Circumpolar Current, is approximately 700 m^2/s at 1500 m depth. The estimate is based on an extrapolation of the tracer based diffusivity using output from numerical tracers released in a 1/20th of a degree model simulation of the circulation and turbulence in the Drake Passage region. The model is shown to reproduce the observed spreading rate of the DIMES tracer and suggests that the meridional eddy diffusivity is weak in the upper kilometer of the water column with values below 500 m^2/s and peaks at the steering level, near 2 km, where the eddy phase speed is equal to the mean flow speed. The implications of these results for the ventilation of deep water masses and for the representation of oceanic turbulence in ocean models used for climate studies will be discussed.
Dr Emily Shuckburgh, British Antarctic Survey, UKSubmesoscale processes and mixing in the Southern Ocean
Dr Emily Shuckburgh, British Antarctic Survey, UK
Session 3: Southern Ocean overturning and ventilation
Professor John Marshall FRS, MIT, USAResponse of the southern ocean and sea-ice to changing winds
Professor John Marshall FRS, MIT, USA
Biography not yet available
Dr Andy Hogg, ANU, AustraliaCirculation in the Southern Ocean: a conspiracy between wind, buoyancy, eddies and geometry
Dr Andy Hogg, ANU, Australia
AbstractDisentangling the individual contributions of surface wind stress and surface buoyancy forcing to the Southern Ocean circulation is complicated by the dynamical role played by eddies, as well as interactions between flow and topography in this region. Here we show a suite of recent results from idealised (but high resolution) ocean models, which are helping to unravel the governing dynamics of the Southern Ocean. It is now clear that eddies may partially moderate the Southern Ocean response to future changes in wind stress, but that the sensitivity of the overturning circulation and the circumpolar transport differ considerably. Surface buoyancy forcing (both local and remote) plays a strong role in controlling the system response, and is likely to dominate Southern Ocean change on long timescales. Idealised model have the twin advantages of complete equilibration and model efficiency; however, an important caveat on the application of idealised model results is that details of the model topography can dominate the behaviour of the system.
Professor Darryn Waugh, John Hopkins University, USAChanges in the ventilation of the southern oceans
Professor Darryn Waugh, John Hopkins University, USA
AbstractSurface westerly winds in the Southern Hemisphere have intensified over the past few decades, primarily in response to the formation of the Antarctic ozone hole. I will discuss the impact of this intensification on the transport of surface waters into the interior (“ventilation”) of the southern oceans. Measurements of CFC-12 made in the southern oceans in the early 1990s and mid- to late-2000s will be used to show large-scale coherent changes in the ventilation, with a decrease in the age of subtropical subantarctic mode waters and an increase in the age of circumpolar deep waters. Model simulations will be used to examine the possible mechanisms involved with these changes in ventilation, and the possible impact on the oceanic uptake of heat.
Professor Jorge Sarmiento, Princeton University, USASOBOM: new observations of the Southern Ocean system
Professor Jorge Sarmiento, Princeton University, USA
Professor Andrew Watson FRS, University of East Anglia, UKGlacial atmospheric CO2 and role of the Southern Ocean
Professor Andrew Watson FRS, University of East Anglia, UK
Biography not yet available
Session 4: Carbon cycle and biogeochemical processes
Dr Mario Hoppema, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, GermanyPenetration of anthropogenic carbon into the deep Southern Ocean with special emphasis on the Weddell Sea
Dr Mario Hoppema, Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany
AbstractUsing 10 cruises spanning 1984 to 2011, we investigate the time rate of change of TCO2 in the Weddell Gyre (i) along the Prime Meridian, (ii) on the continental slope near the tip of the Antarctic Peninsula, and (iii) at the bottom of the Weddell Sea interior. In the Weddell Sea Bottom Water at the Prime Meridian, the spatial distribution of the increase in DIC bears a high resemblance to that of CFCs, suggesting that the changes in Cant are propagated from the surface. However, other variables like dissolved oxygen and silicate also show trends through time, pointing to non-steady state conditions which might also affect the derived CO2 increase. Near the tip of the Peninsula, the coldest and most recently ventilated waters, hugging the continental slope, exhibit increasing DIC over time in clear dependence of temperature. In the bottom layer of the Weddell Sea interior, no relationship is found between DIC and potential temperature. The mean values of DIC in these waters are observed to have remained essentially constant, suggesting that no significant ventilation of these waters has taken place over the time scale of observations. This finding is in line with the low levels of CFCs at this location.
Steven van Heuven, Centre for Isotope Research, University of Groningen, The Netherlands
Elizabeth Jones, Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Germany
Hein J W de Baar, Royal Netherlands Institute for Sea Research, The Netherlands
Professor Corinne Le Quéré, Tyndall Centre for Climate Change Research, University of East Anglia, UKRecent trends in the Southern Ocean CO2 sink
Professor Corinne Le Quéré, Tyndall Centre for Climate Change Research, University of East Anglia, UK
Dr Dorothee Bakker, University of East Anglia, UKCarbon uptake in the Southern Ocean, where ‘old’ (deep water) and ‘new’ (carbon dioxide from fossil fuels) meet
Dr Dorothee Bakker, University of East Anglia, UK
Dr Robert Anderson, LDEO, USABiological response to variable dust supply in the South Atlantic sediment record