Argo Observing climate variability and change in the global oceans: The Argo Programme. (

Facts  71% of the earth is covered by ocean  To understand the oceans you need to measure them.  2.5m of water has the same heat capacity as the entire depth of the atmosphere.  The ocean has high thermal inertia: temperatures are relatively constant over ocean and in coastal regions.  Even sluggish ocean currents can carry warm or cold water parcels great distances over long time scales.  The ocean and atmosphere transport roughly equal amounts of heat from the equator to the poles.  To determine climate variability and change, need to measure the oceans.  Conventional methods of lowering an instrument from a ship is time consuming and expensive.  Ship methods do not give global/temporal coverage- e.g. no winter data in polar regions. How to measure the world’s oceans  Argo

Global warming ≈ Ocean warming. Ocean temperature is a fundamental index for the state of the climate. Right: from IPCC 5 th Assessment. Energy accumulation in ZJ (1 ZJ=10 21 J). 93% of the total global energy change was ocean warming 0-700m ocean: 64% Melting ice: 3% Warming continents: 3% Warming atmosphere: 1% And: warm water is less dense, and so ‘stands taller’: warming and expansion of sea water accounts for ~1/3 of global sea level rise. Present heat gain by the oceans is 10 ZJ/yr (~0.7 W/m 2 ) Wijffels et al (2016).

The ocean salinity field has changed– both at the surface and at depth 50 years of salinity change Fresh places have gotten fresher. Salty places have gotten saltier. The hydrological cycle has ‘accelerated’.

Argo: a global array of drifting profiling floats Provide global near real-time measurements of upper-ocean heat and salt and velocity at 1000m. Data freely available from two Global Data Centres: Currently 3814 floats, 29 countries

What Argo floats do: floats that sink. Provide global near real-time measurements of upper-ocean heat and salt and velocity at 1000m. Float cycle: 1)Sink to 1000m and park for 9 days. 2)Sink to 2000m, then ascend to surface, measuring water properties. 3)Transmit profile temperature and salinity data together with position to satellite. 4)Data available over the internet in near- real time. 5)Repeats for a design life of 5 years. 20 min on sea surface 1000 m 2000 m 9 days drifting Collect T/S profile on ascent

The Argo float The float descends and ascends by changing its density. Uses a hydraulic pump to inflate and deflate an external bladder- volume changes, mass stays the same (With the external bladder full, the float has more volume and so less density and ascends). Pumped sensor package to measure T and S Data transmission system: controls communication with satellite. Microprocessors: deal with function control and scheduling. Approx. Weight: 25 Kg Max. operating depth: 2000m Crush depth: 2600m Temperature measured with a thermistor (resistance depends on temperature) Conductivity measured. Combine temperature and conductivity and you can calculate salinity (salty water is more conductive).

What Argo has achieved: transforming global oceanography. The World Ocean Circulation Experiment was a global survey of 8,000 T/S profiles in 7 years ( ). Argo is a global survey of 10,000 T/S profiles every month. All August T/S profiles (>1000 m, ) 20 th Century: 500,000 T/S profiles > 1000 m Argo: 1,500,000 T/S profiles milestone achieved in years of August Argo T/S profiles ( )

Float data. NZ float WMO Deployed south of Chatham Islands 2/4/2010, completed 231 profiles.

Ice-Sensing Floats From early autumn to late spring every year Antarctica’s sea ice almost doubles the size of the continent! There are especially designed ice-sensing floats that check the ocean temperature each time they ascend. If the temperature gets very close to the freezing point, the float will stop heading towards the surface at 5-10 m depth and go back to its parking depth, and try again 7-10 days later. The float stores its profile data in memory. There is enough memory in this type of float to store as many as 68 profiles (although it is usually doesn't need to store more than 40 profiles between contacts with the satellite) Data transmission through the Iridium system is quite fast and each profile can be uploaded in no more than 2 minutes.

Mean dynamic height of the sea surface. Winter mixed layer salinity and depth What we learn from Argo Temperature - heat storage Salinity - freshwater storage Temperature and salinity give density- ocean dynamics. Water mass formation and characteristics Ocean circulation and transport Large-scale ocean dynamics Climate variability e.g. El Niño Global change assessments Near-real time: now-casting and forecasting Global mean temperature anomaly, °C, 0 – 2000 m Black: global Red: Southern Hemisphere Blue: Northern Hemisphere

New Missions Deep Argo Now we measure the ocean above 2000m, we want to know about the changes below 2000m to measure all of the system. Bottom Water warming from 1990’s to 2000’s Purkey and Johnson (2010) Bio-Geochemical Argo Argo floats work well to measure the global ocean, want to add sensors (e.g. Oxygen, Chlorophyll, pH) to address other concerns. A regular Argo float with T and S sensors (right) and a SOCCOM floats with biogeochemical sensors (left)

~1300 Argo floats deployed by New Zealand’s RV Kaharoa since 2004 for US, Australia, and NZ Argo New Zealand’s contribution

Argo and the classroom Statistical investigations (Level 2-4) Nature of Science strands: Understanding about Science Investigating in Science (Level 3-4) argofloats.wikispaces.com Procedural writing Adopting an Argo Float Science experiments Cartesian Divers Salt water circuits

Procedural writing List the procedure on one strip of coloured paper (The “What”) Draw a line after each step and take another strip of paper and match the lines up. In each section made, describe the “how” or “why” From here, paragraphs can be drafted, using words like ‘first, second etc., then, finally, proceeding, following

Adopting a Float

Science Experiments Cartesian Diver What you need: Plastic bottle Bendy straw Paper clip Plasticine Salt Water Circuit What you need: Wire Light bulb Battery Ice block sticks Foil Salt water