Abstract
This paper demonstrates how the ocean’s meridional overturning circulation brings about effects on the current change in climate by the use of computer models, which are computer-based mathematical models, simulating in three dimensions, how climate conduct its components and the interactions of all these factors. Contradicting the old truism which was used a long time ago to describe how global warming/increased atmospheric carbon dioxide started, the utilization of modern climate models has indicated that the warmer current atmospheric temperatures will in the future cause a decreased meridional overturning circulation of sea waters. These effects will enhance the development of reduced release of radio-carbon depleted carbon dioxide gas and thus the idea of the self-restoration mechanism of the earth to this global warming. Due to these increased atmospheric temperatures, there had been elevated rates of evaporation of surficial ocean waters and rainwater run-offs leading to a high degree of freshening these ocean waters. This further decreases the meridional overturning circulation as the strong hydrological cycle reduces the rate of exposure to deep-sea waters and hence corresponding declined levels of atmospheric carbon dioxide.
Introduction
Since the beginning of the tardy nineteenth century global surface temperatures has increased by an average of about 0.740C (averagely 0.130C per decade), a trend that has doubled from the initial research. This has greatly differed from one area to another as other regions (e.g. Southeastern United States of America and parts of North Atlantic) have recorded a slight cooling in the last century. Higher levels of increased temperatures have been seen in Europe, Asia, and parts of North America at altitudes of between forty and seventy degrees north. The same trends have been shown by the temperatures changes in the adjacent lower and mid-troposphere on recent analyses by use of weather balloon and satellite imaging data (David Easterling, 2007). These observations have been revealed indirectly by indicators of atmospheric warming such as increased borehole temperatures, reduced snow cover areas, and glacier recession indicators, substantially coming into conformity with the more direct indicators of current warmth. This paper discusses the relationship between overturning oceanic circulation and climate warming currently witnessed in our atmospheres, using recent climate models instead of relying on the oceanic winds despite the greater contribution attributed by high human activities (Joellen Russell, 2008).
Would a warmer climate indicate more ocean circulation (Meridional Overturning Circulation) in the future?
About 21,000 years ago in the cold climate of Last Glacial Maximum (LGM), there was a research development on the idea that the cold climate was associated with stronger winds and thus high rate of air circulation in the immediate atmosphere. To some aspects this seemed to be true, for instance it was demonstrated that in winter there is stronger winds and greater thermal contrast within the atmosphere unlike summer. But this is becomingly fairly untrue as it’s now clear that if the winds drive oceanic circulation then stronger winds may have resulted more to a global warming kind of climate, as the rate of overturn of the ocean’s water is high and therefore rate of release of carbon dioxide gas into the atmosphere. The recent trends shows Global changes in temperature limits for instance there is decline in the number of abnormally cold days and nights where as the number of unusually warm days and nights are seemingly elevated. Other than these trends, experiences of notable changes have incorporated expansion of the growing period and decreased number of frost days (J.R. Toggweiler & Joellen Russell, 2008).
Warmer climate in this era of global warming have indicated that in the future there will be decreased meridional overturning circulation of sea waters, due to effects of global warming as depicted by the climate model research. For instance in the Atlantic Ocean, waters seemed to have a weaker overturning circulation at the ages of Last Glacial Maximum1 despite the strong winds recorded at this period (Toggweiler, 2008). Also water in the deep ocean was poorly ventilated and its radiocarbon content was low due to poor ventilation, contrasting to the case in the present times where there is continuously high rate of deep waters overturn in the ocean’s interior by surface waters from the poles.
This Meridional Overturning Circulation started to increase, a factor that highly contributed to the elevated earth’s atmospheric temperatures (what has been referred to as global warming) about eighteen thousand years ago. In the long run the increased overturning of the ocean waters, release a large amount of radiocarbon-depleted carbon dioxide gas (CO2) to the atmosphere leading to the foundation of circumstances causing global warming. Since the idea that Ocean waters mix through the rule of buoyancy (warming, freshening, cooling and Salinification) differences between the interior and external polar surface waters is inconsistent, therefore the overturning of the ocean waters rely on turbulent mixing generated by atmosphere winds and ocean tides.
Climate models being the best research tools on this Meridional Overturning Circulation, has given an implication that raised ocean water temperatures and polar oceanic water freshening play a very vital role in the influence of ocean overturning circulation to development of global warming. A stronger hydrological cycle has indicated that warmer temperatures have led to increased evaporation of tropical ocean waters, and the rains and run-offs which results thereafter in the polar region enhance a high degree of ocean water freshening at their waters (Toggweiler and Russell, 2008). There will be decreased green house gas levels with absorption of heat energy hence reduced effects on atmospheric temperatures & global warming.
What was observed during the Last Glacial Maximum to support or contradict your arguments?
Contrary to climate models and despite its agreement with the general view of winter being more windy than summer and atmospheric temperature differences between the tropics and polar regions, they vary ideas in a great deal. The stronger magnitudes of the winds in the Last Glacial maximum would have led to the intensification in the release of radiocarbon-depleted carbon dioxide gas (CO2) to the atmosphere. Due to the elevated levels of carbon dioxide in the atmosphere hence global warming, the climates at that particular period was expected to show more elevated atmospheric temperatures as compared to the present time, something which was not experienced (Toggweiler and Russell, 2008). This is because the rate of ventilation of the deep Ocean waters would have been high and thus a lot of carbon dioxide gas released by exposure of the deep aged waters, into the atmosphere. But there is a greater agreement that global warming has been caused by elevated levels of atmospheric radiocarbon depleted carbon dioxide gas, and this is what has basically caused disappearance of the ice age.
References
David Easterling and Tom Karl (2007). Global Warming, National Climatic Data Center, Asheville, N.C. 28801. Web.
J.R. Toggweiler & Joellen Russell (2008), Ocean Circulation in a Warming Climate, Relative resource manager-feature (nature vol. 451),