Read chapter 7 Ocean Circulation, Plate Tectonics, and Climate: Climate in The buoyancy flux is the product of the volume flux and the density difference. We think of the climate we enjoy today as normal, however the Earth's climates are Over time, plate tectonic processes cause continents to move to different. Not the least of these effects results from the difference in the thermal properties of Moreover mountain belts formed as a consequence of plate tectonic activity .
An evaporative basin insufficiently concentrated to deposit salt is the most effective source of WSBW. Epicontinental seas as sources of WSBW provide the link by which the solid Earth forces oceanic and atmospheric circulation.
Eustatic sea-level fluctuations can be caused by variations in the global seafloor spreading rate Hays and Pitman, The area of continent flooded by a given increase in sea level is a function of the global hypsography at that time. The size, and hence drainage efficiency, of the continents directly controls the shape of the hypsographic curve Harrison et al. Thus, times of increased seafloor spreading and continental breakup generate large areas of epicontinental seas both by raising sea level and by lowering the elevation of the continents.
The distribution of Mesozoic and Cenozoic evaporite deposits strongly suggests that this zone has remained stationary during the last million years m. Because area is one of the important factors determining the buoyancy flux from evaporative basins, the decrease in the area of evaporative marginal seas over the last m.
Climate in Earth History: The National Academies Press. The decrease in area of evaporative marginal seas and the decrease in the temperature of bottom water during the Cenozoic suggests a transition in the mode of deep-water formation in which cooling at high latitudes has played an increasingly important role, Changes in the latitudinal distribution of epicontinental seas due to the motions of the lithospheric plates also occur.
How Does the Movement of Plate Tectonics Affect Climate Change?
This movement may transport flooded regions into or out of the net evaporation belt. These movements appear to have had little effect on the areas producing WSBW in the Mesozoic and Cenozoic but may have been more important in earlier times.
The chemical state of the ocean at times when WSBW was dominant would have been very different from that which exists at present, and evidence of these differences should be present in the chemistry and isotopic composition of marine sediments. The solubilities of many gases are strongly dependent on temperature and salinity, and Page 87 Share Cite Suggested Citation: As a consequence, WSBW variations should leave a signature in the accumulation rates of organic carbon and carbonate in the deep sea, The distribution of both oxygen and carbon dioxide within the ocean is the result of the formation and destruction of organic matter, exchange with the atmosphere, and physical transport processes.
As a result of respiration by animals and bacteria, oxygen is depleted in most subsurface ocean waters. The longer a water mass is isolated from the atmosphere the lower its oxygen content becomes.
Climate Change due to Plate Tectonics
This fact has enabled oceanographers to use O2 as a circulation tracer. Anoxic conditions develop in deep water when the consumption of oxygen by organisms exceeds the rate of oxygen supply. When anoxic conditions exist, organic carbon accumulates at a higher rate. Deep-sea anoxic events have been observed in the geologic record by many authors e. Many mechanisms have been proposed to explain these events, including stagnation resulting from a layer of fresh or brackish surface water or expansion of the oxygen-minimum layer by inhibited oceanic circulation.
These events may also be explained within the context of our model as resulting from a decrease in ventilation of FIGURE 7. The Mediterranean escapes anoxic conditions owing to the short residence time of its deep waters yr, Lacombe and Tchernia, and its low nutrient content Miller et al.
The CO2 system is of interest because changes in atmospheric CO2 may affect climate by altering the Earth's thermal balance. Dissolved inorganic carbon is present in seawater in the form of bicarbonate and carbonate ions in addition to the dissolved gas.
The ocean is a much larger reservoir of CO2 than is the atmosphere and ultimately determines the atmospheric CO2 content. Significant variations in rates of accumulation of carbonates and organic carbon in the ocean basins suggest corresponding variations in atmospheric CO2 in the past. Thus, at times in the geologic past when WSBW production was large, atmospheric CO2 levels may have been larger than at present and may have played a major role in forcing climate.
We believe that the change to the present climate may be a consequence of the decrease in WSBW production, which is, in turn, a consequence of tectonic and eustatic activity. Two mechanisms may explain the effects of WSBW production on climate: Incoming solar radiation is more intense in low than in high latitudes.
Chapter 5: Section 3 - How Do Plate Tectonics and Ocean Currents Affect Climate?
The outgoing reradiation is also more intense in low latitudes; however, the difference is much less, and there is a net heating in low latitudes. This heating imbalance requires a poleward transport of heat across latitude to maintain the entire Earth's mean temperature distribution in steady state.
This transport is accomplished by sensible heat transport in the atmosphere and ocean and by latent heat transport in the form of water vapor in the atmosphere. The poleward transport of sensible heat in the atmosphere for the same circulation intensity would be curtailed by an equable climate because of the reduced meridional temperature gradient.Plate Tectonics Explained
Lorenz noted that in the present-day atmosphere most of the mid-latitude Page 88 Share Cite Suggested Citation: There would be less available potential energy in an equable climate, and, therefore, this mechanism should be less effective. Manabe and Wetherald suggested that large-scale monsoonal circulations might accomplish the mid-latitude transport of moisture. Our model requires an increase in net evaporation from low latitude marginal seas to produce WSBW and implies a freshening of surface water at high latitudes to inhibit the sinking of cold water.
The link between these two phenomena is higher poleward transport of water vapor in the atmosphere with its equivalent latent heat. Manabe and Wetherald studied the climatic structure in a model atmosphere forced by an increase in CO2 content and found a striking increase in latent heat transport One of the causes for the reduced thermal gradient was the poleward retreat of highly reflective snow cover. With the change in the tectonic plates, this larger land drifted to form different smaller land areas.
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Climate is one of the systems adversely affected by these movements. For instance, a larger land area is likely to follow a strong seasonal pattern of climate. One fine example of the plate tectonics effects on climate is the conversion of the flourishing forests of the Andes Mountains into deserts, leading to increased temperature levels. Interestingly, a study on the Andes Mountains made by scientists at Harvard University suggests the movement of the tectonic plates reduced the amount of rain and further diminished the level of soil erosion.
However, what disturbs the global climate cycle is the change in the location of water bodies that help in regulating heat and moisture on Earth.
Determining Climate Change There are various important indicators that help in determining a change in the climate. Glaciers, insects, vegetation, change in sea level, and dendroclimatology are included in this list.
Many weather stations detect the temperatures, rains, and wind movement too.
Weather balloons and weather satellites are devices that are launched into the atmosphere and space to avail information on the temperature of the globe.
Environmentalists also conduct studies on glaciers to estimate the amount of time since the ice formed in the particular location. The most popular method is that of studying the sedimentary deposits of the Earth.
In addition to these, dendroclimatology helps analyze the level of precipitation.