Saturday, April 28, 2018


Global Warming

Environmental changes caused by global warming seem to be more widely accepted by most, even those living in area with colder than usual weather caused by shifting oceanic currents and the anomalies of air currents and shifts in polar air masses.  A recent increase in melting of shelf ice and discharge of cold water was viewed with alarm as something that might be detrimental to life in the surrounding Southern Ocean.


The crustaceans known as krill serve as intermediates in the food chain  by feeding on algae and then being eaten by others in the food chain; even being directly consumed by the largest whales at the top of the food chain, as well as by fish and others.  Some think the biomass of krill is greater than the biomass of any other animal.

Krill have a life cycle of at least two years beginning with eggs released from adults near the surface of water close to the Antarctic ice-covered water.  The eggs sink and hatch as they are carried by currents of near freezing sea water north from their point of origin.  The eggs hatch and the larvae make their way toward somewhat warmer water near the surface that is moving toward Antarctica replacing and then becoming the cold, northward streaming deeper water.  By then, two or more years later, the larvae have grown into adults that lay eggs beginning another generation that repeats the journey north in cold deep water, and back to the southern point of origin.

Ice shelves

The reduction of ice shelves and increasing flows of melt water from the continental margin may cause some reduction in salinity with increase in temperature.  Over the centuries marine life may have experienced similar changes and developed the ability to survive such changes.  Animals dependent on krill may have to adapt to new locations of krill abundance due their changing environment.

Sea level changes

Shelf ice floating on sea water will not change the level when it melts.  If it has built up after resting on the shallow sea bottom it could raise the ocean level.  If ground ice interface on land warms and contributes to glacial flow into the sea more rise would result.  Since the vast amount of ice in Antarctica is under high elevations of ice it is not likely to be rapidly melted.


The general consensus years ago was that the ice cover was immune to major melting.  It now seems that it is a real danger, but of much less magnitude than melting Antarctic ice would represent.

Joe Engemann     Kalamazoo, Michigan    April 28, 2018

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