The Air-Sea Interaction Profiler (ASIP) is an autonomous vertical profiler. It is developed to study the upper ocean from undisturbed profiles of the water column from a maximum of 100m depth up to the very surface.
The core sensor package on ASIP includes microstucture- and lower resolution temperature and conductivity sensors, shear probes, a PAR sensor and oxygen optode. Apart from that other sensors can be mounted on the profiler and embedded in the data stream, which is stored on an onboard PC. The sensors are mounted at the top of the instrument and the data analysis is focussing on the upward profile.
ASIP is battery powered and can be deployed for up to two days in a row without interference. It’s location is determined via GPS and transmitted to the operator on the main research vessel via the Iridium satellite network.
Image of ASIP from below the water surface, which was published on the cover of JGR
Schematic of ASIP showing the major components of the instrument
Close-up of the sensors on ASIP
ASIP profiling in tank
UltraWave is a device which can provide realtime information on the sea state through ocean wave spectra determination. This is achieved by accurately measuring the ocean surface displacement due to wave motion. From this the energy distribution among different wave frequencies (the ocean wave spectrum) can be computed, from which all parameters which describe the sea state (e.g. significant wave height, wave period and direction) can be derived.
We are currently collaborating with the Irish Naval Service where we have our wave sensing system deployed on the LE Niamh. This provides us with a dataset from which we can develop algorithms to compute the wave spectra using the raw elevation data.
Wind acting on the water surface generates waves which grow in size and eventually break. Wave breaking, commonly known as whitecapping, is perhaps the most important mechanism of transferring momentum, mass, energy and heat across the air-water boundary. Whitecapping entrains air below the water surface, directly enhancing upper ocean mixing and air-sea transfers of gas and heat. Through bursting of whitecap bubbles residing on the water surface, whitecapping is the primary marine source for sea salt aerosol production.
Whitecapping has proven extremely difficult to parameterize and currently poses as major uncertainty in wave models, ocean turbulence models, air-sea gas transfer parameterizations, and aerosol production models. Various techniques, instrumentation and strategies have been employed by numerous research groups to better understand the variability of whitecapping. One such technique involves the separation of whitecaps into actively breaking and decaying stages of evolution. This involves identifying whitecap regions in an image and then distinguishing each region as actively breaking (colour-coded blue) or decaying whitecaps (colour-coded green).
Recently, the Air-Sea Physics Lab at NUI Galway have conducted a large effort to quantify whitecapping using sea surface imagery obtained during the Knorr11 and SOAP campaigns. A large number of sea-surface images (130,000) were used to quantify the presence of whitecapping over a wide range of meteorological conditions.
Whitecap regions within each of the images were manually distinguished as either actively breaking whitecaps (Wa) and decaying whitecaps (Wb). This effort led to the most extensive data set of Wa and Wb to date.
Four stages of a breaking wave resulting in whitecapping at the ocean surface.
Attempts to relate whitecapping fraction to wind speed over the past 4 decades.
Determining regions of interest (ROI's) for stage-A and stage-B whitecapping.
The ocean and atmosphere are a couple system which permanently exchange momentum, heat, gases, aerosols, and freshwater. A better understanding of these fluxes is paramount for our ability to forecast the weather or model the climate.
We use the Eddy Covariance method to directly measure these fluxes as the covariance of the vertical motions in the air with, the along wind motion, the air temperature, or the concentration of gases like CO2 or water vapour.
Since we conduct these measurements from ships at sea we need to apply corrections for the motion of the wind sensor and any distortion of the air flow cause by the ship. As part of our research we constantly refine these corrections in order to improve the quality of our measurements.
Eddy covariance flux mast deployed on the R/V Tangaroa during the SOAP cruise in 2012.
Making flux measurements under high wind conditions in the Southern Ocean
Measured wind speed from the flux mast (upper) and after motion correction (below)
Jetsam is a neutrally buoyant platform which can be programmed to maintain itself at a constant depth. This is carried out by actively adjusting its density through the inflation of an oil-filled bladder.
A Nortek signature-1000 ADCP is mounted on the Jetsam platform to study turbulent velocities at the ocean surface.
Jetsam platform with the Nortek Signature-1000 attached