Climate Change Hypothesis

Introduction 
There has been a vast amount of energy devoted to developing climate change models. These appear to have been largely focused on dividing the surface of the globe into ever smaller increments and summing the effect of higher carbon dioxide concentration in the atmosphere on groupings of such increments to provide regional predictions of climate change effects. This emphasis on the atmosphere fails to account adequately for many other physical, chemical and biological processes that are or may be involved. These notes attempt to redress the balance by hypothesizing on the possible involvement of these other factors. More specifically, this analysis is based particularly on Ice Age dynamics and the lessons we can learn relevant to present-day climate. While to most people the Ice Age is impossibly remote and seemingly divorced from current realities, it is possible that the processes set in place between 100,000 and 15,000 years ago are still dominating our environment. More specifically, it is suggested that the terrestrial system has two dramatically different modes of operation, and under appropriate conditions can switch abruptly from one to the other in the course of one or two decades, which might be soon upon us. This possibility makes it important to understand the drivers behind these two modes of operation simply described as the ‘cooling’ and ‘warming’ modes. 

The ‘Cooling’ Mode

Ocean Circulation
The important influence that the oceans have on the climate of our ‘water planet’ are recognized in references to La Nina and El Nino and even more importantly to the Gulf Stream in moderating the climate of Europe. Further, it is recognized that the flow of the Gulf Stream toward the Arctic results from the sinking of large volumes of cold, salt-dense water off Greenland to the ocean floor driving the global ‘thermohaline’ system, commonly referred to as the ‘Great Ocean Conveyor’. It is further recognized that dilution of the Arctic Ocean by melting Arctic ice lowers the surface water density to the point that it no longer sinks. Under these conditions the Gulf Stream will slow and eventually stop in the Arctic, taking a more southerly course around the Sargasso Sea in the mid-Atlantic. The consequence of this change of flow is that temperatures in Europe will cool by 10*C to 15*C, and ice caps will reform and gradually spread during the succeeding 100,000 years.

Next Ice Age Vulnerability
Recent sampling of the North Sea indicates salinity is decreasing, and observations of Arctic Ice and Greenland glacier melting suggest we may be approaching the conditions that will slow and eventually halt the Great Ocean Conveyor, thereby forcing the Gulf Stream into a more southerly path.

No Circulation – surface consequences
The solubility of carbon dioxide in cold sea water is much higher than in warm tropic surface water, and the water sinking off Greenland carries large quantities of atmospheric CO2 into the ocean depths where it is sequestered for centuries, ultimately for millenia. The CO2 concentration in the atmosphere would therefore be expected to rise when the conveyor is slowing. Further, the reduced volume of water sinking off Greenland implies a corresponding
decrease in deep water rising in the Pacific circulation. This deprives the surface waters of a supply of nutrients from the ocean floor, notably iron, and a corresponding reduction in surface phytoplankton activity and carbon sequestered in the resulting organic detritus.

No Circulation – deep consequences
Study of Antarctic Ice cores has shown that once this cooling trend in Europe is established, it continues to deepen for 100,000 years, with the Earth’s surface becoming progressively colder, drier, windier and the atmosphere dustier. During this time, in the absence of deep ocean water circulation, the carbon dioxide concentration of the deep water increases as a result of bacterial decomposition of the organic material settling from the surface. Dissolved oxygen is depleted; atmospheric dust also settles into the depths where, in the absence of oxygen, iron on the dust surface dissolves as ferrous chloride and soluble bulk nutrients such as nitrogen and phosphorous also accumulate.

Salt Build-up
During this 100,000 year cooling cycle water evaporates from the warm, equatorial oceans and accumulates as ice at the poles and, as a consequence, the ocean level drops 120 metres and the salinity of the ocean surface gradually increases.

The ‘Warming’ Model

Flipping the Switch  Eventually, the salinity of the Arctic Ocean rises again to a level at which the density of the surface water exceeds that of the deep water and starts sinking, thereby restarting the Great Ocean Conveyor. A corresponding flow of deep water in the tropical Pacific rises to the surface carrying with it the carbon dioxide, ferrous chloride and nutrients accumulated over the 100,000 years of the Ice Age. This up-flow permits release to the atmosphere of the vast quantity of carbon dioxide sequestered at depth, while providing the iron and nutrients to support a tremendous phytoplankton bloom. The bacterial decomposition of this algal matter on the ocean surface generates large amounts of volatile dimethyl sulphide that seed low level cloud formation, which, coupled with rising atmospheric CO2 concentrations, slows the loss of infra red energy from the Earth’s surface. This leads to progressive warming of the ocean surface, more evaporation and cloud formation, all facilitating a rapid demise of the Ice Age.

Conclusions Sea level data suggest that at the end of the last Ice Age this abrupt transition into the ‘Warming’ mode, started 15,000 years ago and was essentially completed 7,000 years ago. Since then, the sea level and temperature have been in a state of dynamic equilibrium with only relatively minor fluctuations. The recent increase in atmospheric CO2 concentrations may be a reflection of the progressive failure of the Ocean Conveyor, reducing the volume of upwelling nutrient laden deep water to the ocean surface and in turn the capacity of the ocean phytoplankton sink for CO2. Short-term global warming, by stimulating melting of Arctic ice to further dilute the surface waters of the Arctic Ocean, may presage another abrupt change in Earth’s operating mode to a long-term cooling cycle and the next Ice Age. 

Ice Age Dynamics Hypothesis

(Discussion Waterloo U February17, 2011)
The opportunity to review and discuss the Ice Age Hypothesis was much appreciated. The validity of the hypothesis which addresses only the temperature cycles in the last million years rests on a number of assumptions that need further checking.
Initiation of the cooling trend at the peak of the warming trend

1.     Proposition: The Ice Age is initiated by excessive fresh water dilution of the Arctic Ocean and far North Atlantic preventing formation of the dense (cold, salt) water thought to derive the Ocean conveyor.
Question: Does warming of the Tropical Ocean drive result in a sufficient increase in precipitation into the Arctic region generate a flow off surface fresh water off Greenland sufficient to stop the sinking of cold dense water thought to drive the Ocean Conveyor?

2.     Proposition: The major increase in precipitation in the Arctic reverses the flow through the Bering Strait eliminating a source of sensible heat into the Arctic.
Question: What is responsible for the flow of water through the Bering Strait into the Arctic Ocean and how does this affect the Arctic heat balance?

3.     Proposition: The Gulf Stream without the current induced by the sinking of cold dense water is no longer drawn northward and follows a more conventional surface gyre circulation at lower latitude.
Question: Is the sinking of the cold dense water off Greenland responsible diverting the Gulf Stream into the Arctic? 

4.     Proposition: The loss of the sensible heat of the Gulf Stream and the flow through the Bering Strait results in cooling of the Arctic Ocean.  This factor coupled with the continued high regional precipitation induced by the still very warm tropical ocean greatly increases the quantity and seasonal persistence of snow in the region amount, the increased albedo reinforcing the cooling effect. 
Question: Is the Gulf Stream when not drawn into the Arctic region by sinking of the cold dense water driven entirely by the action of the Westerly winds or does thermal expansion of water by solar heating in the Gulf of Mexico contribute by raising the water elevation in that region providing a continually regenerated hydraulic head that must flow somewhere?

5.     Proposition: The closing of the Isthmus of Panama 3 million years ago eliminated leakage of warm Gulf of Mexico water into the Pacific Ocean increasing the flow of warm water into the North Atlantic.
Question: The Ice Age cycle chart shows an immediate response coincident with the closing of Panama but if linked why is it only in the last million years that the cycle frequency changed from 40,000 years to 120,000 years coupled with a doubling of the magnitude of the cooling.

6.     Proposition: Matichenkov orbital cycles do not correlate well with Ice Age cycles and while they may provide a ‘nudge’ marginally influencing the cycles, terrestrial influences are dominant.
Question: What does a statistical correlation show?

Process Postulated for Termination of the Ice Age

1.     Proposition: Water evaporated in the tropics is transferred to the Arctic (and Antarctic) where it is fixed as ice, the tropical surface water thereby increases in salinity  and when carried poleward by the ocean gyres it cools and intermittently sinks into the deep ocean water this sinking being counter-balanced by rising deep water elsewhere The magnitude and persistence of this effect increases as the sea level Falls, temperatures cool and the salt content of the ocean surface increases eventually reaching a critical level where circulation can be sustained and sufficient nutrients and carbon dioxide is released the 100,000 year accumulation to sustain warming trend. 
Question: Do sediments or deep ocean analysis provide any evidence of such a process occurring?

2.     Proposition: The atmospheric concentration of CO2 decreases over the 100,000 year cooling period of the Ice Age and there is a reduction in the inventory of terrestrial biomass.
Question: Where and how is this CO2 stored?

3.     Proposition: In the postulated that in the absence of deep water circulation during most of the cooling period a small proportion of the biological mass in the surface water settles into the deep water and is decomposed by bacterial action liberating nutrients and building up a high CO2 concentration in the bottom water that is partially and periodically released due the overturning of the ocean initiated by sinking cold salt surface masses delivered to cold regions of the ocean by the ocean gyres.
Question: Where else could the carbon be stored?

4.     Proposition: Renewed deep water circulation at the end of the cooling cycle leads to release of CO2 and nutrients that encourage an extensive phytoplankton bloom reinforcing the warming effect of additional CO2.
Query: How can this effect be substantiated?