Tag Archives: sea level rise

Climate Ocean Linkage

In recent years there seems to be somewhat of a kerfuffle over the use of the terms Global Warming and Climate Change. Some in denial about the scientific concerns for changes in our planetary environment have suggested that “they” have changed the terminology to confuse the public. Or denialists claim that the term climate change is employed to cover up for the fact that the planet is not actually warming. Nothing could be further from the truth.

Both terms have been around and in use for years by scientists and mean different things. Realistically climate change is a result of global warming and includes many derived effects in addition to warming. The best way to look at is yet more terminology. Anthropogenically (man-made) driven changes to our planet include overall warming, which directly drives things such as warmer land and sea temperatures, the melting of the polar ice sheets and the recession of glaciers. All of the above has been going on and accurately measured for a couple of centuries. The rate of change is not always constant but the trend is undeniable.

The warming is due to something called radiative forcing. Certain gases produced through human activities, mainly burning fossil fuels, absorb infrared energy (heat ) in the atmosphere. The heat is trapped in the atmosphere rather than radiated out to space. Essentially planetary heat gain and heat loss are out of balance. Carbon Dioxide not only drives the heat cycle but also negatively impacts the oceans.

The oceans are getting warmer due to the direct heating effect, and as there is more water from melting ice, the salinity or saltiness of the oceans is decreasing. Coral bleaching is being observed around the world. Bleaching is the term given to the die-off of coral due to heat and acidity. All that is left is the lifeless exoskeletons which appear white without the living matter present. Coral makes up the reefs that constitute the nurseries of the much of the ocean fish populations.

Wetlands on the continental shelves are being drown from rising sea levels. Wetlands also constitute nurseries for fin fish and shellfish stocks which are threatened. As the water levels rise the brackish water moves farther inland. Jellyfish, which have little nutritional value and therefore aren’t part of a food chain seem to be replacing other valuable organisms around the globe.

The world’s oceans are actually acting to moderate the rate of global warming by absorbing some the Carbon Dioxide from the atmosphere, but this comes at a cost. As the Carbon Dioxide from the atmosphere dissolves in the oceans, it reacts chemically to become more acidic. The same effect is achieved in bottled soda drinks. Carbon Dioxide is the stuff that makes a soft drink fizzy, and also more tart, due to the acidity. The acidity of oceans is directly proportional to the amount of Carbon dioxide absorbed. The worst case scenario is that Calcium Carbonate, the stuff of shells and the bones of animals won’t form.

All these changes are being accelerated by what are known as positive feed back loops. As sea ice melts the surface of the earth becomes less reflective. Less reflectivity means more heat absorption, which leads to more sea ice melting. The longer we delay action the more difficult our predicament becomes.

Global Warming; Freshwater, Saltwater

Will fighting over freshwater replace fighting over oil? The snowpack in mountains has been exploited by humans since the beginning of civilization. The slow release of water as the snowpack melts provides not only drinking water but also water for irrigation of crops where seasonal rainfall is insufficient.

Billions of people around the world depend on melt water. The regions which include the western United States, Alpine Europe, Central Asia and downstream of the Himalayas and Tibetan Plateau contain nearly nearly half the human population of the planet. Global warming is threatening the timely delivery of freshwater. More cold season runoff can overwhelm reservoir storage of water, and less warm season runoff means less water for irrigation during the growing season.

Researchers at Stanford have published a paper examining the projected impact of global warming and water resources, especially those related to the snowpack in the northern hemisphere. Using the average and extreme rates for precipitation, accumulation and runoff for the 30 years from 1976 to 2006 as a baseline, they then used computer modeling to project out through the 21st century.

They found that as global warming intensifies, low snowfall years will increase, and the snow melt will occur sooner, disrupting water management. “”While the greatest impacts are likely to occur at higher levels of global warming, our results highlight the fact that continued emissions over the next few decades are likely to substantially reduce snow accumulation in a number of regions, increasing the risk of both flooding and drought in different parts of the year,” said the lead author of the paper.

A second, obvious threat posed by global warming is the melting of ancient land bound ice. As the ice reservoirs on the antarctic continent, Greenland, and other interior glaciers melt away, sea levels will rise threatening the great coastal cities of the world. Sea level rise is happening now and recent data suggests that it is happening at an accelerating rate.

Based on long term measurements of tidal gauges and more recent satellite data, on average the rate of sea level rise from 1880 to 2013 has been 0.06 inches per year. If one looks at more recent data however the rate of rising is much greater, over twice as fast. Looking at data from 1993 to the present shows a rate of change of sea level of 0.14 inches per year. Taking account of the accelerating rate of change of sea levels, experts predict a sea level rise of up to 6 feet by the end of the century.

It is extremely difficult to stop the seas from rising but by active approaches to slow global warming we can slow the rate of change of sea levels, giving us more time to protect coastal populations through mitigation.

Sea Level Rise

Global warming is the result of somewhat complex atmospheric dynamics which can result in a warmer planet, stronger storms, both floods and droughts, political instability and elevated sea levels. Probably the simplest of these outcomes to understand is sea level rise. If it gets warmer ice melts to water and drains into the oceans, raising the global water level. Additionally as the oceans warm, the warmer water takes up more space and adds to sea level rise.

Those that deny the risks of global warming might say that melting icebergs or the melting of the north polar ice won’t change sea level and if that is all you consider, it is true. But there is much more ice trapped on land in the form of glaciers, the Greenland ice sheet and the vast Antarctic ice sheet. Enough in fact to raise the level of the seas eighty meters, or over two hundred and fifty feet.

A sea level rise of two hundred fifty feet would leave only Lady Liberty’s head above the New York Harbor. Only the tippy-tops of the skyscrapers in most coastal cities will be above water. The Atlantic coastal plain, South Florida, and the state of Louisiana will be fishing grounds.

This level of rising seas is the worst case scenario based on hundreds of years of unabated burning of fossil fuels, according the Intergovernmental Panel on Climate Change. So what about sea level rise in the near term, say within the twenty first century? There are people alive today who will see the turn of the next century. If the combustion of fossil fuels is not reined in, a modest projection is a two meter (over six feet) rise. If anything combustion of fossil fuels is accelerating due to advanced recovery techniques like horizontal drilling and fracturing.

The impact of a two meter rise in sea level varies from a minor nuisance to a catastrophe depending on location. Some islands in the South Pacific are already suffering from the one quarter of a meter rise over the past one hundred years or so.costal The combination of rising sea level and more severe storm surges due to global warming are causing coastal erosion. Increased salinity of the remaining soils which decreases agricultural productivity is as troublesome as the erosion.

The real catastrophe is the flooding of large coastal cities. Miami, New Orleans, and Tampa are three of those at greatest risk because most exist at sea level already, and are also sensitive to more flooding due to tropical storms and hurricanes. Estimates of fifty billion dollars per city per year may be necessary to prevent or mitigate damage due to flooding.

The most recent experience with severe coastal flooding was due to Hurricane Katrina. Economic losses to Louisiana and Mississippi are estimated to be over one hundred fifty billion dollars.
Our thrust for the cheapest energy up front may very well cost us a lot more when all the costs are accounted for. Solar, wind, and geothermal which don’t drive global warming are looking cheaper every day.