Dedicated to the balanced discussion of global warming
This article discusses a series of events that have already started that could cause the next ice age. This series of events is the same as the one that theories say caused the last ice age. It is an interesting series of events that seems just as likely as the world getting dramatically warmer. In fact, since many of the mechanisms are already in place, this likelihood seems even stronger.
I usually put the title of the article that I am referencing in the title of my post but in this case the title resides in a technical journal and it is so boring that I elected to write my own. For the purposes of this discussion, I am referencing “Climate Control Requires a Dam at the Strait of Gibraltar” which was published by the American Geophysical Union on July 8, 1997 by the now Professor Emeritus Dr. R. G. Johnson.
The scientific article suggests that if the Mediterranean Sea continues to increase in salinity, it will eventually cause warm water to flow to the Labrador Sea (off the coast of Newfoundland and Greenland) and cooling of the Nordic Seas (east of Greenland). This warm water increases the humidity of the area which causes glaciers to form and causes Northern Europe to begin to cool. This appears to be the way that the last major ice age was triggered.
The difference now is that the increase in salinity of the Mediterranean Sea has been accelerated by the damming of the Nile River. Since the majority of the fresh water from the Nile is no longer reaching the Mediterranean, the Sea is getting more saline. Compounding this may any increase in evaporation due to higher temperatures caused by global warming, which would further accelerate the tipping point of the Mediterranean Sea.
This hypothesis is far from proven but it does point to the complexity of the worlds climates. It also points out that Man may be influencing the world in a way that we do not understand and therefore we must be careful to not rush into a “fix” that could cause more harm or be ineffective but costly.
If the Mediterranean Sea continues to increase in salinity, shifting climatic patterns throughout the world may cause high-latitude areas in Canada to glaciate within the next century. The Mediterranean is starved of freshwater by human activities: most of the annual flow of the Nile River is now used for irrigation and no longer enters the sea. The sea surface evaporation losses are also increasing as the surface warms due to rising CO2 concentrations in the atmosphere. Consequently, the Mediterranean hydrologic deficit is steadily increasing. The deficit is the difference between the larger amount of water lost by evaporation and the smaller amount received from rainfall and river inputs. The difference is made up by a two-way exchange of water with the Atlantic at Gibraltar. Barring a significant change in regional atmospheric circulation, these two human modifications of the environment will cause the salinity of the Mediterranean to increase for some time as fossil fuels are consumed.
Although it is commonly thought that the last ice age began in Canada when diminishing Milankovitch summer insolation cooled the climate, circulation changes that increased moisture advection to ice sheets were probably more important. Frequent storms moving into Baffin Island and other areas in the presently arid Canadian subarctic more likely caused the ice age.
The upwelling apparently behaves like a fluidic switch that warmed the Labrador Sea and caused Canadian ice sheet growth while cooling the Nordic Seas and northern Europe. In this conceptual model of glacial initiation, the switching is controlled by the hydrologic deficit of the Mediterranean and the resulting outflow. Thus the hydrologic deficit is a critical link in a chain of circulation and climatic factors that began with low insolation, weak African monsoons, and drought in the headwaters of the Nile and culminated with new ice-sheet growth in Baffin Island and other regions in northern Canada.
If all the Nile flow entered the Mediterranean, the hydrologic deficit would be approximately 31,000 m3 s-1, estimated from Mediterranean outflow and inflow volumes and salinities at Gibraltar, river discharges, and an assumed steady state. A larger hydrologic deficit due to the loss of Nile River discharge is the main difference between today and 120,000 years B.P. in the chain of factors in [the flow diagram above].
CO2 warming would probably trigger a new ice age by increasing Mediterranean evaporation losses, independently of Nile discharge. If CO2 warming increases the sea surface temperature by 2°C, as predicted when atmospheric CO2 doubles in the next 70 years, the increase in the hydrologic deficit of 14%, as estimated from the ratio of future/present vapor pressures at the sea surfaces, would exceed the effect of Nile loss. The combined CO2 warming and Nile loss might increase the hydrologic deficit to 23%. New ice sheet growth and a much colder Europe would then become extremely likely, and CO2 concentrations will continue to rise.
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