Sea Level Rise

The processes that are projected to induce global sea level rise. Solar radiation is absorbed by the oceans of the world and this heat causes thermal expansion of the ocean water. The water melting from the glaciers and ice caps of the world are causing additional sea level rise. The melting polar caps inject cold, heavy water to the world’s oceans, which sink and flow towards the equator where it is heated, rises and completes the cycle flowing back towards the poles
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Current sea level rise is occurring at a rate of around 1.8 mm per year for the past century, mainly it is widely believed as a result of human-induced global warming. This rate may be increasing. Measurements from the period 1993–2003 indicated a mean rate of 3.1 mm/year.

It is believed unmitigated global warming will continue to increase sea levels over at least the coming century. Increasing temperatures result in sea level rise by the thermal expansion of water and through the addition of water to the oceans from the melting of continental ice sheets.

There is no physical capacity of humans to protect against long-term sea level rise. Since greater than 75 percent of the human population lives within 60 km of a coast, it is important that sea level rise be limited to the greatest extent possible to minimize loss of life, and economic and ecological impacts.

Thermal expansion, which is well quantified, is currently the primary contributor to sea level rise and is expected to be the primary contributor over the course of the next century. Glacial contributions to sea level rise are believed to be less important, and are more difficult to predict and quantify.

Values for predicted sea level rise over the course of the next century typically range from 90 to 880 mm, with a central value of 480 mm. Based on an analog to the deglaciation of North America 9000 years ago, some scientists predict sea level rise of 1.3 m in this century. However, models of glacial flow in the smaller present-day ice sheets show that a probable maximum value for sea level rise in the next century is 800 mm, based on limitations on how quickly ice can flow below the equilibrium line altitude and to the sea.

For the purpose of this invention the 480 mm value or .48 m is used for comparative purposes.

A simple model to demonstrate sea level rise due to thermal expansion assumes that the ocean consists of two parts: the surface ocean and the deep ocean. The surface ocean is uniform in depth, temperature, and salinity. The depth of the surface ocean is 500 m. The average initial temperature of the upper ocean is 14oC. The deep ocean is everything else, and is assumed to not change.

The volume of water in the ocean is given by the equation: V=A*d, where A is the surface area of the ocean and d is the depth of the ocean. The mass of an object is equal to its volume multiplied by its density; m=V*ρ. Therefore d = m/(ρ*A). The problems is to find the changes in sea level Δd, which =d-d0, where d0 is the initial height of the ocean, 500m.

Change in depth (sea level rise) is a function of density and the assumption for the purposes of this calculation is that the mass of the ocean and its surface area do not change. It is also assumed for the purposes of this calculation that the salinity of the ocean remains constant. The oceans density therefore is dependent solely on temperature. Since it has already been assumed the sea will rise by .48m over this century, this equates to a 4.4°C increase in the temperature of the ocean, which is the increase in ocean temperature used in other calculations in this application

Sea level rise will change the amount and pattern of precipitation, likely including an expanse of the subtropical desert regions. Other likely effects include Arctic shrinkage and resulting Arctic methane release, shrinkage of the Amazon rainforest, increases in the intensity of extreme weather events, changes in agricultural yields, modifications of trade routes, glacier retreat, species extinctions and changes in the ranges of disease vectors.

Sea temperatures increase more slowly than those on land both because of the larger effective heat capacity of the oceans and because the ocean can lose heat by evaporation more readily than the land.

Glacial isostatic adjustment (GIA) is causing some coastal lands to sink, increasing the rate of sea level rise for those areas. In some areas of the world, GIA is causing land to rise allowing for some compensation to rising sea level.

A 2008 study by a group of U.S. scientists found that the economic damages from hurricanes has increased in the U.S. over time due to greater population, infrastructure, and wealth on the U.S. coastlines, and not to any spike in the number or intensity of hurricanes.

They found that although some decades were quieter and less damaging in the U.S. and others had more land-falling hurricanes and more damage, the economic costs of land-falling hurricanes has steadily increased over time.

A paper published in Natural Hazards Review, found that economic hurricane damage in the U.S. has been doubling every 10 to 15 years because more and more people continue to move to the hurricane-prone coastlines. The researchers for this paper used two different methods, which gave similar results, to estimate the economic damages of historical hurricanes if they were to strike today. The first method utilized population increases at the county coastal level, while the second used changes in housing units at the county coastal level. Both methods used changes in inflation and wealth at the national level.

The results of their study indicates that if the 1926 Great Miami Hurricane were to hit today, it would cause the a loss of between $140 billion to $157 billion, compared to Hurricane Katrina, causing the second most damage at $81 billion.
The team concluded that potential damage from storms – currently about $10 billion yearly – is growing at a rate that may place severe burdens on exposed communities, and that avoiding huge losses will require a change in the rate of population growth in coastal areas, major improvements in construction standards, or other mitigation actions.
There are two types of inundation that will be caused by sea level rise: permanent inundation and episodic inundation.
A higher sea level will provide a higher base for storm surges. A one-meter rise in sea level would enable a 15-year storm to flood areas that today are only flooded by 100-year storms. Flood damages would increase 36-58% for a 30-cm rise in sea level and increase 102-200% for sea level rise greater than 90 cm. Larger storms cause loss of beach width and force large sediments into inlets.

Although the frequency of hurricanes may not be increasing due to global warming it is clear rising sea levels will increase the damage they produce.

Rising sea levels would allow saltwater to penetrate farther inland and up streams. Higher salinity impairs both surface and groundwater supplies. This effect would impair water supplies, ecosystems, and coastal farmland. Saltwater intrusion would also harm aquatic plants and animals as well as threaten human water supply.

The penetration of saltwater can be compared to what occurs during extreme droughts when river runoff is diminished, forcing a fallow period in agriculture

In addition to damage to ecosystems, sea level rise promotes saltwater intrusion into coastal aquifers. A freshwater lens overlies saltwater along barrier coasts, and volcanic and coral islands. This freshwater lens is 40 times thicker than the elevation of the water table above mean sea level Therefore each increment of sea level rise reduces the freshwater capacity of the lens by 40 times.

It is an objective of the current invention to limit the expected threat from sea level rise by generating power from a portion of the heat that would otherwise induce thermal expansion in the oceans and to sequester desalinated ocean water, which would otherwise inundate populated areas and produce other hazardous environmental effects, in the world’s arid deserts.