Tracking Ocean Salinity from Space using Colour
February 19 2018 - 9:30AM
JCN Newswire
Measuring salinity at the ocean's surface is important for
tracking global ocean circulation as well as local ecosystem
health. A research team from Universiti Malaysia Terengganu have
proposed a new method to measure sea surface salinity using ocean
colour as a proxy. Reported in the Pertanika Journal of Science
& Technology, this method could improve monitoring frequency
and resolution, particularly for coastal areas.
Salinity is the concentration of salt ions in a volume of water.
While the total salt content of the ocean remains fairly stable,
salinity can vary as the ocean's volume changes when fresh rain,
river water and melted ice enter the ocean, and when seawater
freezes or evaporates. Some areas get saltier and others fresher as
these processes occur, collectively known as 'the hydrological
cycle'.
Besides affecting marine organisms, salinity is also a key player
in ocean circulation. Saltier, denser water sinks beneath lighter,
fresher water, helping drive the massive conveyer belt carrying
seawater around the world. A space-based satellite currently
measures sea surface salinity all over the globe using a metric
called 'microwave emissivity'. The Aquarius satellite, operated by
the U.S. National Aeronautics and Space Association (NASA), takes
one measurement for every 150 square kilometres of ice-free ocean,
passing over the same spot once a week.
Marine scientist Md Idris Suffian and colleagues wondered if they
could use images taken from another pair of satellites that cover
the entire ocean daily, and on a much more detailed scale - one
picture for every one square kilometre. To do this, they needed to
confirm that they could use ocean colour captured in the optical
images to determine salinity.
Ocean colour is partly determined by how much organic matter is
dissolved in the water, which gives it a green, yellow or brown
tint, rather than the usual blue. By testing seawater samples taken
along the east coast of Malaysia during different seasons, the
researchers found a reliable inverse relationship between the
amount of coloured dissolved organic matter (CDOM) and salinity.
Based on this relationship, they were able to develop a
mathematical algorithm that could be used with the satellite images
to derive salinity. They use the colour data captured in the
images, specifically in the deep blue part of the spectrum, to
determine the amount of organic matter, and then compute
salinity.
The researchers note, however, that the performance of the
algorithm may vary from region to region, depending on the degree
of mixing between freshwater and seawater. Especially in areas with
heavy river flows and high levels of organic material, the
conservative relationship between dissolved organic matter and
salinity could be altered so much that it no longer fits the
algorithm. They recommend further testing to improve the
algorithm.
For more information about this research, please contact:
Dr. Md. Sufian Idris
School of Ocean and Environmental Sciences
Universiti Malaysia Terengganu
Email: suffian@umt.edu.my
Phone: +609 668 3284
The original paper is available at: http://bit.ly/2Bs2At1
About Pertanika Journal of Science & Technology (JST)
Pertanika Journal of Science & Technology (JST) is published by
Universiti Putra Malaysia in English and is open to authors around
the world regardless of nationality. Currently, it is published
twice a year in January and July. Other Pertanika series include
Pertanika Journal of Tropical Agricultural Science (JTAS), and
Pertanika Journal of Social Sciences & Humanities (JSSH).
Pertanika Journal of Science & Technology aims to provide a
forum for high quality research related to science and engineering
research. Areas relevant to the scope of the journal include:
bioinformatics, bioscience, biotechnology and bio-molecular
sciences, chemistry, computer science, ecology, engineering,
engineering design, environmental control and management,
mathematics and statistics, medicine and health sciences,
nanotechnology, physics, safety and emergency management, and
related fields of study. http://www.pertanika.upm.edu.my
For more information about the journal, contact:
The Chief Executive Editor (UPM Journals)
Office of the Deputy Vice Chancellor (R&I)
IDEA Tower 2, UPM-MDTC Technology Centre
Universiti Putra Malaysia
43400 Serdang, Selangor, Malaysia
Phone: +603 8947 1622 | +6016 217 4050
Email: nayan@upm.my
Distributed for Pertanika Journal of Science & Technology by
ResearchSEA.
Source: Pertanika Journal
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