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)