Dr Anthony Galea, science lecturer and researcher at the University of Malta, tells us how scientists forecast ocean and sea movement, with some help from jellyfish and rubber ducks.
How have rubber ducks helped scientists understand the sea?
During a storm in January 1992, thousands of rubber ducks fell from a shipping container and have since been drifting with the ocean currents. Their appearance on shores around the world gave scientists information about the main ocean currents.
Nowadays, slightly more sophisticated equipment – satellite observations and other sensors at sea – give us a broader understanding of the oceans' movement. That includes sea circulation, what causes water movement and how water flows interact. This knowledge enables scientists to predict the mood of the sea.
How long have people been using sea forecasts?
Mariners have always tried to understand the mood of the sea, often by observing meteorological changes.
The sea forecast is similar to the weather forecast. Both atmosphere and sea are fluids, and their movement is governed by the mathematical Navier-Stokes equation – an equation from classical physics which describes the flow of fluids.
When these equations are converted into numerical models – long lists of computer codes – they can indicate the movement of air or sea for the next few hours or days.
What has changed recently in sea forecasting, especially near coastlines?
Mathematicians and computer scientists are improving numerical models to provide more accurate sea forecasts, at higher spatial resolution. These high resolution forecasts are like watching a movie on a big screen, rather than on a mobile phone.
Oceanographers can use these models to work out what sea currents near the coast will look like. A main sea current would generate eddies – smaller movements at the edge – which can be modelled using the latest mathematical techniques. The fate of your floating, inflatable beach flamingo can now be predicted.
Researchers are also using past observations of sea currents, plus numerical models, to produce more realistic sea forecasts. This technique is called data assimilation.
Who is using this new information about the movement of water?
Mariners, divers, fishers, lifeguards, and policy makers. A lot of marine human activity is found close to the shores; for example, fishing and tourism. As a result, many people need to know what complex coastal currents will do.
Information also helps protect coastal habitats. Divers use high-resolution sea forecasts to plan their dive and limit the risks of sub-surface sea currents. Fishers and boaters use the predicted sea surface currents to reduce fuel by limiting the boat’s drift. Coastal authorities need detailed sea forecasts in case of an accidental oil spill, and other floating material at sea.
Why are jellyfish dispersion forecasts important?
Nobody wants to swim in a jellyfish-swamped sea. When a bloom – or large amount – of jellyfish hits a coastal area where there are lots of tourists, such as bays or beach resorts, the commercial sector takes a hit. Swimming and sea activities are paralysed.
But swimmers need not beware. Since jellyfish drift with sea currents, oceanographers can predict their trajectory with numerical models. This provides an early warning system of an approaching bloom of jellyfish, so that bay authorities can secure the swimming area with jellyfish nets.
Similar to jellyfish movement, oceanographers can also forecast the fate of oil spills to help contain and clean up the oil.
How do you expect sea forecasting to change in the future?
As computer processing gets more advanced, more accurate simulations will be calculated in even less time.
One day, we may be able to access continuous sea forecast updates from our mobile phones, helping mariners navigate the sea, allowing swimmers to enjoy calmer beaches, and surfers to surf the best waves.
Anthony is a lecturer and researcher at the Physical Oceanography Research Group, Department of Geosciences, Faculty of Science, University of Malta. He is this year’s winner of FameLab Malta and will compete at the FameLab International Final at Cheltenham Science Festival.
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