HOW HIGH IS THE OCEAN?

A well known Irving Berlin song asks "How Deep Is The Ocean?" However, more recently, scientists have been singing a different tune: "How High Is The Ocean?"

A recent report states that computations of global sea-level increases in the period 1900 to 1990 have been over-estimated by as much as 30%.* That could be good news. However, since 1990, according to the report, it is estimated that sea levels significantly have accelerated, creating fresh concerns. That is not so good news.

According to the report, there may be several possible causes for the recent sea level increases, including global warming, changes in patterns of ocean currents, and melting of ice sheets in Greenland, the Arctic and Antarctica.

Part of the challenge in attempting to more accurately measure global sea level changes is selection of measurement models and methodology. One cannot sail the oceans with a mammoth yardstick. Generally, it seems that reliance has been placed on records from regional ocean tide gauges, which then are averaged. However, the report asserts, such simple averages are not accurate. Therefore, new estimates have been developed using modeling of the physics behind sea level "finger prints", using simulation and statistical methods.

Perhaps another cause of ocean level increases has been overlooked: all the trash that is polluting the seas. According to another report, it is estimated that there are 5.25 trillion pieces of waste plastic floating on the oceans, weighing 270,000 metric tons.** The smallest pieces of plastic are said to sink or become eaten by fish and other sea creatures.

Maybe it is time for a new ballad: "How Trashed Is The Ocean?"

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* Reuell, "Sea Level Correction", Harvard Gazette,
January 20, 2015

** "The Trash Man", Science News,January 24,2015,p.4