Sea levels rising, lake levels falling

Everyone knows that ocean waters are rising — threatening coastal cities, flooding farms, endangering the economics of ports and turning off visitors to Venice.

But not all water levels are rising. The reverse is true in some large lakes, and that’s worrying experts. The problem for them isn’t the melting of ice sheets and glaciers that add water but evaporation that takes water away.

One studied example is the Caspian Sea, the world’s largest lake that’s located between Europe and Asia. Researchers at the University of Bremen in Germany say that water levels there could fall by an astonishing 50 feet by the end of this century. The effects: damaged fisheries, disappearing habitats, ruined economies, geopolitical strife.

The Caspian, which is fed by the Volga River, has no natural outflow to the ocean. Its water level is determined by (a) how much water the Volga supplies, (b) how much rain and snow fall from the sky and (c) how much evaporates into thin air.

That last point is important in a warming planet because warm air can hold more moisture than cool air.  

The web site Science Daily, citing Bremen research this month, says that unless current trends change, coastal ecosystems in the Caspian will be “transformed beyond recognition”:

“The expected escalating effects of Caspian sea level decline are likely to lead to a wholesale reorganization of ecosystems, and threaten unique Caspian biota that have been evolving in the basin over millions of years.”

 The report also raises possible economic and geopolitical consequences:

“Coastal infrastructure including ports will become obsolete as waters recede. Shrinkage of the Caspian Sea might further affect future claims by the five littoral states on the coveted oil and gas reserves. Maritime zones of jurisdiction and exclusive fishing rights will shift. Growing international political tensions would be expected regarding the reallocation of fishing grounds or national water extraction and desalination plans to help meet the increasing demands of the agricultural, industrial, and household sectors in water-stressed regions.”

The disturbing effects of falling water levels aren’t theoretical. The Environmental Protection Agency has reported that between 1997 and 2000 low water levels in the Great Lakes forced ships to reduce their cargo tonnage by 5 to 8 percent, thereby raising shipping costs.

Other studies have found other effects, such as increased cases of algae blooms. A good source is the North American Lake Management Society.

Meanwhile, NASA has produced a striking visual report on the shrinkage of the Great Salt Lake in Utah. Just how significant lake shrinkage can be (sometimes also thanks to droughts and overuse) is dramatically shown by the image of the Mongolian lake that illustrates this blog posting.

In fact, the effects of climate change are numerous and sometimes surprising. For example, the increasingly intense downpours that we’re experiencing can cause lake waves to get larger, leading to erosion and flooding problems that are commonly associated with high water.

As noted above, climate instability affects oceans , too. One impressive source of information is Sofar Ocean, whose data-collecting skills can tell us a lot: check out this report.

Bottom line: climate instability is causing some waters to rise and some to fall, causing varieties of unplanned consequences along the way.

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