The deep, cold water flows into the South Atlantic, Indian, and Pacific Oceans, eventually mixing again with warm water and rising back to the surface. Changes in water temperature and salinity, depending on how drastic they are, might have considerable effects on the ocean conveyor belt. Ocean temperatures are rising in all ocean basins and at much deeper depths than previously thought, say scientists at the National Oceanic and Atmospheric Administration NOAA.
Arguably, the largest oceanic change ever measured in the era of modern instruments is in the declining salinity of the subpolar seas bordering the North Atlantic. Robert Gagosian, president and director of the Woods Hole Oceanographic Institution, believes that oceans hold the key to potential dramatic shifts in the Earth's climate.
He warns that too much change in ocean temperature and salinity could disrupt the North Atlantic thermohaline circulation enough to slow down or possibly halt the conveyor belt—causing drastic climate changes in time spans as short as a decade.
The future breakdown of the thermohaline circulation remains a disturbing, if remote, possibility. But the link between changing atmospheric chemistry and the changing oceans is indisputable, says Nicholas Bates, a principal investigator for the Bermuda Atlantic Time-series Study station, which monitors the temperature, chemical composition, and salinity of deep-ocean water in the Sargasso Sea southeast of the Bermuda Triangle.
Oceans are important sinks, or absorption centers, for carbon dioxide, and take up about a third of human-generated CO2.
Data from the Bermuda monitoring programs show that CO2 levels at the ocean surface are rising at about the same rate as atmospheric CO2. But it is in the deeper levels where Bates has observed even greater change. In the waters between and 1, feet and meters deep, CO2 levels are rising at nearly twice the rate as in the surface waters.
While scientists like Bates monitor changes in the oceans, others evaluate CO2 levels in the atmosphere. In Vestmannaeyjar, Iceland, a lighthouse attendant opens a large silver suitcase that looks like something out of a James Bond movie, telescopes out an attached foot 4. Two two-and-a-half liter about 26 quarts flasks in the suitcase fill with ambient air. In North Africa, an Algerian monk at Assekrem does the same. Around the world, collectors like these are monitoring the cocoon of gases that compose our atmosphere and permit life as we know it to persist.
When the weekly collection is done, all the flasks are sent to Boulder, Colorado. There, Pieter Tans, a Dutch-born atmospheric scientist with NOAA's Climate Monitoring and Diagnostics Laboratory, oversees a slew of sensitive instruments that test the air in the flasks for its chemical composition.
In this way Tans helps assess the state of the world's atmosphere. Walking through the various labs filled with cylinders of standardized gas mixtures, absolute manometers, and gas chromatographs, Tans offers up a short history of atmospheric monitoring.
In the late s a researcher named Charles Keeling began measuring CO2 in the atmosphere above Hawaii's 13,foot 4,meter Mauna Loa. The first thing that caught Keeling's eye was how CO2 level rose and fell seasonally. That made sense since, during spring and summer, plants take in CO2 during photosynthesis and produce oxygen in the atmosphere. In the fall and winter, when plants decay, they release greater quantities of CO2 through respiration and decay.
Keeling's vacillating seasonal curve became famous as a visual representation of the Earth "breathing. Something else about the way the Earth was breathing attracted Keeling's attention.
He watched as CO2 level not only fluctuated seasonally, but also rose year after year. Carbon dioxide level has climbed from about parts per million ppm from Keeling's first readings in to more than ppm today.
A primary source for this rise is indisputable: humans' prodigious burning of carbon-laden fossil fuels for their factories, homes, and cars. Tans shows me a graph depicting levels of three key greenhouse gases—CO2, methane, and nitrous oxide—from the year to the present. The three gases together help keep Earth, which would otherwise be an inhospitably cold orbiting rock, temperate by orchestrating an intricate dance between the radiation of heat from Earth back to space cooling the planet and the absorption of radiation in the atmosphere trapping it near the surface and thus warming the planet.
Tans and most other scientists believe that greenhouse gases are at the root of our changing climate. The three lines on the graph follow almost identical patterns: basically flat until the mids, then all three move upward in a trend that turns even more sharply upward after We know their radiative properties," he says.
Exactly how large that effect might be on the planet's health and respiratory system will continue to be a subject of great scientific and political debate—especially if the lines on the graph continue their upward trajectory. Eugene Brower, an Inupiat Eskimo and president of the Barrow Whaling Captains' Association, doesn't need fancy parts-per-million measurements of CO2 concentrations or long-term sea-level gauges to tell him that his world is changing. In his fire chief's truck, Brower takes me to his family's traditional ice cellars, painstakingly dug into the permafrost, and points out how his stores of muktuk—whale skin and blubber recently began spoiling in the fall because melting water drips down to his food stores.
Our next stop is the old Bureau of Indian Affairs school building. The once impenetrable permafrost that kept the foundation solid has bucked and heaved so much that walking through the school is almost like walking down the halls of an amusement park fun house. We head to the eroding beach and gaze out over open water. We continue our tour. Barrow looks like a coastal community under siege.
The ramshackle conglomeration of weather-beaten houses along the seaside gravel road stands protected from fall storm surges by miles-long berms of gravel and mud that block views of migrating gray whales. Yellow bulldozers and graders patrol the coast like sentries.
The Inupiat language has words that describe many kinds of ice. Piqaluyak is salt-free multiyear sea ice. Ivuniq is a pressure ridge. Sarri is the word for pack ice, tuvaqtaq is bottom-fast ice, and shore-fast ice is tuvaq. For Brower, these words are the currency of hunters who must know and follow ice patterns to track bearded seals, walruses, and bowhead whales.
There are no words, though, to describe how much, and how fast, the ice is changing. A ribbon lake is a long, narrow lake. The water in the lake fills a trough, or hollow area in the ground. This trough once contained soft rock that a glacier carved out long ago. Erratics are large rocks that have been carried, often long distances, from where they originally were by a glacier.
A floodplain is a flat valley floor beside a stream that becomes flooded from time to time. Flooding occurs when the stream overflows, such as after heavy rain or when mountain snow melts. A pyramidal peak is a mountain peak, or top, left when a glacier has worn away all the sides of the mountain.
It has this name because it looks like a pyramid. Global warming has caused them to be less stable, to move faster towards the ocean, and add more ice into the water. If the Greenland Ice Sheet melted or moved into the ocean, global sea level would rise approximately 6.
If the West Antarctic Ice Sheet were to melt or move into the ocean, global sea level would rise approximately 8 meters. Skip to main content. Meltwater at the top of the Greenland ice sheet flows through a hole in the ice, down to the base. In recent years the ice has been melting faster, and water at the base causes the ice to move faster towards the ocean. Image: University of Colorado Most of us do not live in polar regions. Melting ice causes more warming. Melting permafrost releases greenhouse gases.
Less ice on land means sea level rises. Image: University of Colorado.
0コメント