Southern Ocean Air-Sea Flux Observations
Eric Schulz, CAWCR, BoM
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Motivation
• The Southern Ocean is large (22% of world ocean) and is expected to play a significant role in the global climate system
• Role in the carbon, heat and mass cycle? • Very few in situ observations due to harsh and
remote nature• Poorly constrained for these air-sea fluxes
– How much carbon is trapped in the deep ocean?– How much heat absorbed, transported and released?
• The Sub-Antarctic Zone occupies half of the Southern Ocean and is a region of extensive surface water subduction
Observation Programs
• IMOS funded, lead by the Bureau– Data freely available– 3 research vessels, broad spatial coverage but
patchy in time and space– 1 mooring, 1 location, continuous presence– Collaboration and piggybacking (mooring)
encouraged– Mooring program uses MNF vessel for annual
visits
Sustained Ocean observatory• Multidisciplinary (met ,ocean, bio-geo-
chemical (BGC)• Multiple platforms
– SAZ mooring (sediment traps) – transfer of carbon to deep ocean
– Pulse mooring (BGC) – consumption of CO2 in mixed layer
– SOFS mooring (weather, fluxes, CO2 physical ocean) – physical fluxes through ocean surface
– Gliders (physical and BCG) – spatial context & vertical profiles
– Drifting Profilers (physical and BGC) – spatial context & vertical profiles
Southern Ocean Time Series
SOTS Location
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Southern Ocean Time Series ObservatoryFunded by IMOSOperated by Bureau, CSIRO & UTAS3 Moorings Gliders & Profiling Floats
46.75oS, 142oE350 NM SW of TasmaniaSub-Arctic Zone with strong biological activity
Situated centrally in the Sub Antartic Zone, Australian sector of the Southern Ocean
Pilot deployment flux buoy at 60S 140E,2012, JAMSTEC SOFS and JAMSTEC 60S mooring locations in
Australian sector of the Southern Ocean.
SOTS 47S 142E
SOFS Observations
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Short- & Long-wave radiationWind
Temperature & Humidity
Precipitation
Air pressure Tower and instruments
• Wind• Air Temperature & Humidity• Long- & Short-wave Radiation• Rain• Pressure• PAR,• pCO2• Waves• SST & salinity• BGC
• Oxygen• Fluorescence
• Sub-surface 10-500m• Temperature• Salinity• PAR• Pressure• Currents• Particle size
Data availability 1998-2012
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Started with SAZ sediment traps in 1997
Added Pulse BGC in 2009 – summer only, annual since 2011
Added SOFS in 2010
Dedicated profilers (2005) & gliders (2010) halted in 2011 with technical issues
Gaps in SAZ are due to Instrument and mooring failures
SOFS example observations: Wind speed and Solar Radiation
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
9-month refurbishment gap Between SOFS 1 & 2, now back-to-back deployments
Winds peaking ~50kts
Distinct solar radiation annual cycle
SOFS3 data is hourly real-time, so less variabilitythan SOFS1&2
Buoy Refurbishment
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
Net deployment ocean cooling of 10 Wm-2
Asymmetric seasonal signal in NetIncoming SW dominates seasonal signal
Severe short-term ocean turbulent cooling events (>400 Wm-2) with cold, dry southerly winds.
Frequent ocean heating events from Hs
Ocean heat content shows trend agreement with air-sea flux on seasonal scale.
See: Schulz et al. 2012, GRL.
SOFS applications: Air-Sea FluxesBulk Fluxes from SOFS-1, March 2010- March 2011
Ship Observations
• IMOS Underway ship flux facility• Provides instruments to complete existing
sensor suite, data telemetry & processing, routine calibration and real-time quality controlled data delivery
• Recruited – Southern Surveyor, April 2008– Aurora Australis, September 2010– Tangaroa, April 2011
Ship Instrumentation
• 1-minute averages telemeterd every 1-3 hours.
• Automated QC of observations and generate flux products and delivered to IMOS ocean portal
• Equipment will be transferred from Surveyor to Investigator
The Centre for Australian Weather and Climate Research
A partnership between CSIRO and the Bureau of Meteorology
RV Southern Surveyor
• Rain• Wind• Air Temperature & Humidity• Pressure• PAR• pCO2• SST & salinity• Currents• Long- & Short-wave Radiation
Data coverage 2008-2012
4ox4o Gridded net heat flux 2008-2012Summer: Oct-April Winter: May-Sept
(+ve = ocean cooling)