Ice Floats

Woods Hole Oceanographic Researcher Luc Rainville prepares to deploy a Polar Profiling Float in the seasonal ice zone of the Beaufort Sea. The ice-strengthened Iridium antennae and hardened outer hull protect the float from damage as it ascends under ice.
An AWI Apex float being deployed in the Weddell Sea. These floats are equipped with an ice-avoidance algorithm that allows the float to ‘detect’ the presence of ice above (by measuring water temperature as it ascends).

 

The polar oceans of both hemispheres are important for deep ocean ventilation and the sequestration of heat and gases (including carbon). The Southern Ocean connects the global ocean basins and regulates the overturning circulation. The exposed Arctic Ocean will affect ocean and atmospheric circulation, moisture and heat fluxes. Therefore, both polar regions play a critical role in setting the rate and nature of global climate variability through their moderation of the earth’s heat, freshwater and carbon budgets.
 
Recent studies suggest that some of the strongest climate change signals are already underway in the high latitudes. Routine, sustained observations are required in order to detect, interpret and understand global climate change.
 
Argo has revolutionised observational oceanography over the past decade by providing more profiles than collected historically through ship-based hydrography. The original design of the Argo mission specified nominal 3 x 3 degree spacing, with 10 day sampling interval, of the oceans between 60 ˚N and 60 ˚S, excluding the high latitudes and marginal seas. The exclusion of the high latitudes was due to the inability of early floats to sample under sea-ice. Technological advances in float design in recent years now give us this capability. Advancements have come through re-design of hardware (i.e. ruggedised ice floats with ice-hardened antennae), software (ice-avoidance algorithms and open-water test) and communications (Iridium), allowing the transmission of stored winter profiles.
 
IMOS EIF funding has made it possible for Australia to deploy 18 floats in the seasonal ice zone in the Australian sector of the Southern Ocean. Our ice floats are successfully withstanding the harsh conditions in the ice zone and have survived several winters, storing their under-ice profiles and telemetering the data in spring.

 

Schematic of the float cycle for a Polar Profiling Float