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5.13: Coastal Plains, Climate Change, and Predicted Sea-Level Rise

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    Coastal Plains, Climate Change, and Predicted Sea-Level Rise

    Climate change is a theory that has growing significance as overwhelming evidence shows that observable changes have been and are occurring in the atmosphere and oceans. Several factors are responsible. First, the natural cycles of continental glaciation associated with cyclic changes in the amount of solar energy the polar regions the Earth receives (ice ages are discussed in more detail in Chapter 9). The second factor is the modern impact of greenhouse gases on global warming created in the modern era of industrialization.

    Impact of Melting Glaciers On Sea-Level Rise

    Global warming has been taking place since the end of the last ice age, and the impact of sea level rise caused the melting of the massive continental glaciers is easily observable (this is discussed more detail in following chapters). The peak of the natural part of latest global warming cycle may have happened nearly 7,600 years ago, as warming of the atmosphere and the associated sea level rise drastically slowed down at about that time. The peak of the last ice age, about 26,500 years ago when massive continental ice sheets, ice caps, and alpine glaciers cover much of northern Europe and North America, more extensive glaciers in Antarctica (Figure 5.39). This displaced nearly 10 million cubic miles of ocean water onto the land to be stored as ice. Research shows that onset of deglaciation began about 20,000 years ago in the Northern Hemisphere with a massive rise in sea level starting starting about 14-15,000 years ago with deglaciation of the West Antarctic Ice Sheet. The location of shelf breaks around the world shows that sea level has risen about 400 feet (120 meters) since the peak of the last ice age.

    Continental Glaciers
    Figure 5.39.
    Extent of glaciers and sea ice during the peak of the last ice age and today in the Northern Hemisphere.

    The effects of sea-level rise is very obvious on the landscape. Perhaps most obvious are that coastal river valley are now submerged in seawater in most locations around the world. If example, Chesapeake Bay and Delaware Bays were a river valleys about 400 feet deep at the peak of the last ice age; it is now submerged as salt-water estuaries (Figure 5.40).

    Chesapeake and Delaware Bays and the Delmarva Peninsula
    Figure 5.40.
    Chesapeake and Delaware Bays (estuaries), and the Delmarva Peninsula. Sea-level rise has back filled river valleys draining into the Atlantic Ocean. Ridges on land became peninsulas.

    Global Warming and Sea Level Rise have happened many times in the geologic past.

    Figure 5.41 shows a map of the Fall Line. The map also shows the location of Fall-Line Cities along the inland margin of the Atlantic and Gulf coastal plains). The Fall line is an imaginary line, marked by waterfalls and rapids, where rivers descend abruptly from an upland to a lowland. Historically, it is the location that major cities became established because it was the farthest point up a river ships could travel before they encountered rapids, waterfalls, or conditions too shallow for ships to continue farther inland. In the Eastern U.S. the imaginary fall line is between the Appalachian Piedmont and the Atlantic coastal plain physiographic provinces. Similar fall lines can be observed along coastal plains in locations around the world. In the United States, the Fall Line boundary roughly follows an elevation of about 60 meters (200 feet) above sea level, This elevation is what sea level was before glacial ice started forming on Antarctica and Greenland when the Earth was ice free about 35 million years ago. At that time, the entire Atlantic and Gulf Coastal Plains were submerged and were part of the continental shelf. Since then sea level has risen and fallen many times as continental glaciers have formed and melted. Sea level is now rising again, but cause of that increased rate is what is the problem.

    Fall line cities
    Figure 5.41
    . Fall line cities on along the inland margin of the Atlantic and Gulf coastal plains.

    The Great Problem of Our Times: Accumulation of Greenhouse Gases In The Atmosphere

    The demand for energy and agricultural resources by the world's expanding human population began to increase significantly since the beginning of the Industrial Revolution in the mid 1900s. Awareness of the environmental impact of this consumption began to become obvious most obvious when air pollution levels first began to intolerable in large urban regions around the world beginning in the 1960 (on into the present). With satellite technologies and collaborative international action in gathering of atmospheric and oceanographic data the Scientific Community is gathering and presenting evidence of active changes taking place around the world. These changes are caused by the introduction of vast quantities of greenhouse gases from the burning of fossil fuels (coal, oil, gas) and from deforestation and poor agricultural practices (soil destruction and livestock). The world's Scientific Community almost unanimously agrees that the effects of climate change are very real. Projections are being made about the plausible impacts climate change is going to have on the destruction of ecosystems, the rise in sea level.

    The environmental impacts of climate change associated with greenhouse gas emissions are monumental. Here is a partial list:

    • A summary of scientific research presented in 2013 by the United Nations' Intergovernmental Panel on Climate Change (summarized by by the Washington Post in 2016) suggests that sea level rise is estimated to rise between 0.52 and 0.98 meters (1.7 and 3.22 feet) by the year 2100, with other estimates ranging higher. This report also suggest that melting of ice on Antarctica alone could cause seas to rise more than 15 meters (49 feet) by 2500.

    Global temperatures have risen by 1.5° Celsius since the pre-Industrial Era began, and this increase is projected to continue with the most significant rise happening in the past 20 years on an annual basis. A 2° Celsius rise alone is projected to have catastrophic impacts on ecosystems around the world. Warm-climate species will expand their ranges to the detriment of cold-climate species on all levels on of the world's food chains (oceanic and terrestrial). Estimate reported by the Natural Resources Defense Council suggest that global warming may cause the global temperature by as much at 8° Celsius by 2100 if the projected consumption of fossil fuels and other releases of greenhouse gases continues unmitigated.

    • Global distribution of rain fall is expected to change, and major tropical storms are expected to increase in intensity.
    • Increased level of CO2 in the air is increasing the acidity of ocean surface waters, negatively impacting many species.
    • Arctic regions are particularly experiencing climate change impacts involving the gradual disappearance of sea ice, the melting of permafrost, and the rapidly increasing rate of melting of glaciers.

    Examples: The effects of sea-level rise are quite obvious in Louisiana (where the land is sinking and eroding, Figure 5.42). Figure 5.43 shows how the Gulf and Atlantic coastal regions will change with a rise of 1, 2, 3, and 4 meters. Figure 5.44 shows the 4 meter water line in Washington DC. It will be interesting to see how the political world will deal with these changes!

    The political and economic consequences caused by inaction to stop potential calamities caused by climate change are staggering to ponder. The world faces economic crisis driven, in part, by the conflicting greed by international carbon-gas-producing industries, and largely by the increasing demand for energy and natural resources by individuals to entire nations that are unable or unwilling to accept their share of responsibility.

    Land loss in Louisiana Sea Level Rise in Florida 4 meter sea level rise in Washington DC
    Figure 5.42. 50 years of land loss from sea level change and coastal erosion in Louisiana. Figure 5.43. Projected changes from 1,2,3, & 4 meters of sea-level rise on the East Coast. Figure 5.43. Projected flood zone of Washington DC if sea level rises 4 meters. Congress will have to paddle canoes to get to the White House!

    Here is a quote the human impacts from climate change published by Human Rights Watch [2018] (a global environmental watch media organization):

    "As the world urbanizes and industrializes, and as effects of climate change intensify, environmental crises will increasingly devastate the lives, health, and livelihoods of people around the globe. A lack of legal regulation and enforcement of industrial and artisanal mining, large-scale dams, deforestation, domestic water and sanitation systems, and heavily polluting industries can lead to host of human rights violations. Activists and ordinary citizens defending their rights to land and the environment may face intimidation, legal harassment and deadly violence. The primary victims of environmental harm are often impoverished and marginalized communities with limited opportunity to meaningfully participate in decision-making and public debate on environmental issues, and have little access to independent courts to achieve accountability and redress."