Changing Antarctic Climate


THE CO2 CONNECTION                                                                 
Earth’s climate is changing more rapidly these days and in a direction that is due to the increase in heat-trapping gases in the lower portion of our atmosphere --- the Troposphere --- or at least that is what 99% of scientists, who have investigated it, say is happening. The evidence is overwhelming and is no longer a “belief” but a fact. That means these gases --- carbon dioxide, methane, ozone and others ---  are increasing in the Troposphere, the lower part of Earth’s atmosphere (20 km/12 mi thick at Equator; but only 7 km/4.3 mi thick at the Poles). This has been happening since the dawn of the industrial revolution around 1850, along with the accelerating increase in Earth’s human population, use of fossil fuels, and increases in all their gas-emitting livestock and the destruction of carbon-dioxide-(CO2)-consuming forests. The warming, GLOBAL WARMING IT IS CALLED, occurs because the greater concentration of these gases absorbs more of the heat that is radiated by the surface of the Earth than it used to; that surface is warmed by Sun’s radiation (sunlight). Much less of the light/heat energy is escaping back into space these days. Yes, it’s like a greenhouse and this is called the “greenhouse effect.” Most of any contention among climate scientists in regard to CLIMATE CHANGE --- the more valid term for what is happening --- is about the rate at which the atmosphere will warm, and what the results will be and not so much anymore what the causes might be. Yes, volcanoes can pump greenhouse gases into the atmosphere, or can pump more dust/soot into the air (causing cooling); and, yes, the output of the sun can (and does) change and, yes, shifts in the Earth’s orbit do occur and contribute to warming or cooling BUT THESE FACTORS CAN’T ACCOUNT FOR THE RATE OF WARMING NOW BEING OBSERVED.

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This is a NASA photo of the Space Shuttle Endeavour (taken 21 Sept 2012). The orange layer is the Troposphere, with all its heat-trapping gases, moisture and clouds. The white layer is the Stratosphere.
While the “weather” has become very unstable leading to --- at least during the period of time since the Last Glacial Maximum (ended 10,000 years ago) --- unprecedented heat waves and droughts in some areas and rainfall and floods in others, what is most dramatic is the warming of the oceans, even if the average warming of surface waters is only around 0.9C. That is HUGE! Water is the most difficult substance there is to heat (that’s, for instance, why it’s used to cool nuclear reactors). It takes more energy to raise one cubic centimeter of water one degree Celsius than any other substance. As water is heated, to a point, it expands, and that plays a huge part in how much sea level has risen during the Industrial Age (since 1850), about 2/3 of a foot (~20 cm) on average. More and more, though, melting land ice (and not melting sea ice) is contributing to sea level rise.

The warming of the oceans, and the land, is leading to altered placements of persistent low and high atmospheric pressure centers, and in turn wind patterns and Jet Stream shifts in location. This changes storm tracks. This changing wind patterns is the most important aspect of climate change and is important especially for Antarctica. As the middle latitude oceans warm, and the Antarctic continent stays cold, the atmospheric pressure gradient between high (Antarctic) and low (surrounding ocean) pressure is getting stronger. This, in part (see below), has led to accelerating circumpolar winds. This change has had a huge effect on the seasonal formation and disappearance of sea in the high latitude Southern Ocean.

Antarctica’s climate is changing somewhat in response to this “global warming” but also because of another human-caused process, THE DEPLETION OF OZONE IN THE STRATOSPHERE, which leads to the ANTARCTIC OZONE HOLE. There is a lot more to lessened atmospheric Ozone than the fact that more ultraviolet light from the sun is getting through (easier to get a sunburn, and contract skin cancer). Very few people, including scientists, until recently have openly discussed this phenomenon because it is complex and confuses the story about “global warming.” The news media, from which the public gets most of its information, can deal only with simple stories, and often not even those very well.

Ozone is a major component of the Stratosphere, and is formed in a process using the energy contained in ultraviolet light from the Sun. The Stratosphere is colder than the Troposphere, due to the thinner gases (lower greenhouse effect), but is warmer than it would be due to the presence of Ozone. The gases that humans use in their air-conditioners (some spray cans, and other appliances) escape and find their way to the Stratosphere. At the low temperature of the Stratosphere especially over Antarctica, these gases, called chloroflourocarbons (CFCs) are able to break up Ozone. This process occurs especially over Antarctica because the Troposphere is thin (as noted above) and the continent is high (the South Pole is at 2800 m/9300 ft) and, therefore, represents one big ice cube projecting up through the Troposphere. If you’ve ever climbed a high mountain, you’ve discovered that the air gets colder as you approach the summit; it gets colder as you go higher owing to thinner air and less ability to hold heat (it’s called adiabatic cooling). In the Troposphere, as you climb higher above the mountain (in an airplane), the air gets even colder. Once you get to the Stratosphere, however, this cooling by higher altitude no longer occur. In fact, though it’s still very cold, it begins to get warmer with more altitude (and more Ozone), but over the Poles not as much as it did before the release of CFCs began in mid-1900s.  The chemical reaction that destroys Ozone requires it to be very cold; that’s why the Ozone Hole occurs over Antarctica. Countries have tried to ban the use of CFCs but have not succeeded. Oh well! They have a long way toward solving global warming as well.

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Thanks to NASA, the Antarctic Ozone Hole looks like this during the cold of winter; it gets slightly smaller during summer when temperatures of the Troposphere and lower Stratosphere are warmer due to Sun’s radiation.

Due to increasing CFC’s since the mid-1900s and the decrease of Ozone in the Stratosphere, the lower Stratosphere over the Antarctic has cooled ~9C. That is a huge change!! This changes the air pressure difference between the Antarctic continent and the surrounding ocean. At the same time, the oceans of the middle latitudes have been warming, as well as the air above them (or vice versa). Air flows from high pressure (Antarctica) to low pressure (surrounding, warmer ocean). The result is that the Polar Vortex of winds that surround the Antarctic --- the winds that propel the Antarctic Circumpolar Current that isolates Antarctica from the rest of the World’s ocean --- have been increasing in strength.

Because these days there is much more wind trying to get through the gap between the Andes Mountains of southern South America and the Transantarctic Mountains of the Antarctic Peninsula, the Polar Jet Stream is being forced to bend towards the north until it finally pours over the Andes. It then bends way to the south on the other side of South America. As very low pressure systems --- storms --- travel eastward along the Polar Jet, they are sucking cold air off the Antarctic continent where the Jet Stream bows way south (Pacific sector) but sucking warm air from the South Atlantic where it bows way north (Atlantic sector).

The result is that the Antarctic Peninsula, particularly its western coast, is being blasted by warm air from South America and the South Atlantic. This in turn has resulted in sea ice disappearing in this area. At the same time, sea ice has been growing in the Pacific sector. In fact, sea ice has been growing everywhere around Antarctic, or at least not decreasing, owing to another phenomenon, the effect of the Earth’s spin. Any moving object or particle, including water molecules and ice floes, subjected to wind in the Southern Hemisphere is forced to its left due to the Earth’s spin (objects in the Northern Hemisphere are deflected to their right). This --- called the Coriolis Force --- also causes the spin of water draining from a sink or toilet bowl. This is why the Polar Vortex of winds blow the direction they do, clockwise around the Antarctic continent just like the water in draining sinks in the Southern Hemisphere. Finally, this spin, which is increasing, is drawing the sea ice farther offshore in most of the Southern Ocean, particularly the Ross Sea/Pacific Sector.

AND THAT IS NOT EVEN THE WHOLE STORY, THOUGH IT IS THE PART MOST IMPORTANT TO ANTARCTIC PENGUINS. You see, the middle layers of the Southern Ocean, which are formed north of the Southern Ocean but flow south and descend below Antarctic’s surface waters, are warming. This warm layer beneath the cold Antarctic surface waters, is called Circumpolar Deep Water. This warmth is coming from the warming atmosphere in Earth’s middle latitudes (i.e. South America, Australia), as noted above. These warmer waters reach the surface (again owing to the wind and Earth’s spin) along the edge of the Antarctic continent. This is called “ocean upwelling.” These warmer waters, that flow southward and up the sub-sea valleys carved by glacial streams during the Last Glacial Maximum, are melting Antarctica’s ice shelves from the underside! The ice shelves are fresh-water glacier ice and not salt water sea ice. As a result, in part, Earth’s sea levels have been rising and will continue to do so, due both to water expanding as it warms and also to more fresh water input. Estimates are at least another meter (4 ft) of sea level rise in the next 80 years, and that’s the minimum possible. On the other hand, disappearing glaciers, and especially coastal ice shelves, bring more nesting habitat for Adélie Penguins, but see the next section of this discussion.