"Have you watched the film 'Day After Tomorrow?'" asks Professor Charitha Pattiaratchi, here to chair the four-day international seminar on "Physics of Estuaries and Coastal Seas". The subject sounds daunting, but he manages to make it interesting.
The plot of the film includes a theory about the continuous belt of global oceanic currents driven by changes of salinity and water temperature and the kind of disruption it can cause if this process is disturbed. "This oceanic currents system cannot stop overnight like the plot of the movie, but the oceanic current theory is indeed true science that illustrates the importance of studying the physics of the ocean," Professor Pattiaratchi explained.
|Prof. Pattiaratchi while on Oceanographic research using high tech equipment
In an oceanic system, salinity and temperature decide the density of the sea water and density finally defines pressure. So changes of salinity and temperature ultimately create low and high pressure zones in the ocean simulating the oceanic current system that is vital for Earth's climate stability and also for the health of the oceans. The 'Day after Tomorrow' phenomenon involves physics of global level oceanic currents, but changes of salinity and temperature can happen in estuaries where rivers meet the sea at different levels, creating different impacts.
Estuaries that form a transition zone between river environments and ocean environments are always subject to both marine influences, such as tides, waves, and the influx of saline water and riverine influences such as flows of fresh water and sediment. In these estuaries, the freshwater from river systems mixes with the sea water which has different salinity levels, so ocean water that is dense remains in the bottom, but freshwater flows on top layers. "These different water levels are like oil and water which does not easily mix acting as two water bodies in the estuary," Professor Pattiaratchi said.
Usually the freshwater flows from rivers are flushed out to the sea within a few days. But if freshwater that is also bringing lots of nutrients stays long in the estuary, it can affect the water quality and disrupt the ecology of the estuary ecosystem which has been tagged as one of the most productive natural habitats in the world. It is a very fragile system, but future phenomena like sea level rise related to Global Warming will have direct impacts on the hydrology of the estuaries since the estuaries will be the first frontier to face sea level rise.
Oceanic scientists around the world have realized the importance of developing computer models that can predict the effects of sea level rise for the estuaries in the next 50 - 100 years. One of the aims of PECS is also to develop a model which can predict changes in estuary systems as a reaction to environmental changes. Hence management measures to minimize the damages may be taken. "In simpler terms, we are trying to develop a model to predict the changes in weather in estuaries" said Prof. Pattiaratchi.
'Coastal and estuarine observations and modeling' has been adopted as the theme of PECS this year. Around 80 oceanographers from different parts of the world participated in this four-day seminar held at the Mount Lavinia Hotel. The PECS seminar is held once in two years and this is the 15th symposium held since its inception in 1978.
Why Whales off Mirissa?
"Physics of oceans can also be helpful for us to understand the areas of fish abundance," Professor Pattiarachi says. Usually the dense underwater currents are rich in nutrients and at some points in the ocean, they are brought to the surface by upwelling currents. This simulates development of tiny plankton that fish can feed on.
So this food chain goes on helping biodiversity to thrive on some areas.
The PECS International Seminar also provides a forum for junior scientists and engineers working in this field. Asha De Vos, a PhD. student of Prof. Pattiaratchi is currently doing related research on why whales are seen in abundance off the southern coasts of Mirissa and Weligama.
"Whales are giants that have high energy demands. So abundance of food may be a key for the aggregation ," said the young marine biologist. Prof.Pattiarachi also pointed out there are submarine canyons that can attract whales and they are created at points where rivers flow to the ocean.
First Sri Lankan Physical
The first Sri Lankan Physical Oceanographer Prof. Charitha Pattiaratchi holds Bachelors, Masters and PhD degrees from the University of Wales, UK. He has been at the University of Western Australia for over 20 years and currently holds the positions of Winthrop Professor of Coastal Oceanography and Head of the School of Environmental Systems Engineering.
He has played an active role in examining climate change effects in coastal regions of Western Australia particularly in terms of ocean currents, wind and wave climate, sea level variability, coastal flooding and beach stability.
"I've had this interest from childhood," said the Professor, an old Royalist. At school, he was a national level swimming champion and held the 100m under 19 record for 18 long years.