Lesson 2. Antarctic Oceanography: Component I - Ice/Glaciers Component II - Marine Snow

ANTARCTIC

Lesson Objectives: • Introduces students to the different kinds of ice found in Antarctica, • Students will become familiar with ice sheets, icebergs and glaciers. • Marine snow is found in the oceans surround Antarctica. We will discuss what it is and what function it serves to our oceans. Component I - Ice/Glaciers

Antarctica's cold, thick hard whose sides are often bounded covering, called an ice sheet, by mountains or the walls of a began to form 25 million years valley. Ice sheets, or caps, ago. Approximately 98% of which are also formed from Antarctica is covered by ice. compacted snow, are so Antarctica actually changes massive that they cover entire size – during the summer landscapes, mountains as well months (October-March), the as valleys. Glaciers and ice coastal ice melts and Antarctica sheets flow slowly toward the "shrinks." sea where the temperature is slightly warmer. This causes Although almost all of chunks of ice to break off; since Antarctica's land mass is ice is lighter than water, it floats covered by ice, in a few places when it reaches the sea. Once on the continent, mountain these chunks of ice are free- peaks poke through. The floating, they are called Transantarctic Mountains icebergs. The process of divide the areas of the "birthing" an iceberg is called continent known as West and calving. Only about one-tenth East Antarctica. of the iceberg is visible above water. The largest iceberg ever A glacier is a huge mass of ice, recorded measured 200 miles formed from compacted snow, by 60 miles.

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Parts of the West Antarctic ice are less stable than the ice on sheet rest on the sea floor and land. Scientists carefully toward a warmer climate and monitor it to see whether it will begin to melt, leading to a be affected by global warming. sharp increase in sea level If the temperature rises, large which would cause severe parts of the ice sheet will melt flooding on a global scale. and float freely. As they float, these ice sheets will move Component II - Marine Snow

Marine snow is the debris or and denser than the dust that falls through the surrounding ocean, but have oceans and settles on the sea many cavities. While the floor, the same way as dust in particles have to be at least the air settles on an object in one-half millimeter in diameter your home. The difference is to be considered snow, they that this ocean dust is full of can grow to be quite large, on nutrients and life. Marine snow the order of feet, but the are helps transport material from rare. Most marine snow in the the surface ocean to the deeper ocean is 1-2mm in size. layers of the sea. Scientists Marine snow plays an important believe marine snow is a major ecological role by moving food source for life in the atmospheric carbon from the abyssal deep, bringing surface of the oceans to the important nutrients into the seafloor. This can affect the deep sea while carrying with it climate over thousands of years diverse populations of by removing carbon from the microorganisms. This marine atmosphere and transporting it snow consists of bits of dead to the deep sea. Atmospheric animals and plants bound carbon dioxide dissolves in the together by mucus, which is ocean water, and algae take up produced by the ocean the gas as they dwellers. The mucus glues photosynthesize, converting the together scraps of crustacean atmospheric carbon into plant shells, remnants of plants and carbon as the algae grow. The excrement of animals. The algae contribute to the particles are all different shapes formation of the debris that

©PROJECT OCEANOGRAPHY ANTARCTIC OCEANOGRAPHY 101 ANTARCTIC sinks through the ocean in abundant krill feeding on the marine snow. Some small blooming algae produce lots percentage of the total carbon and lots of fecal pellets that remains at the bottom of the sink to the deep-sea. This ocean as marine snow and is process of marine snow and largely consumed by benthic krill fecal pellets settling into the (bottom dwelling) organisms. deep Antarctic over millions of This percentage can be as high years has transported huge as ten percent of the total amounts of algal materials to carbon in coastal waters and the Antarctic sediments. The less than one percent in the result is that these sediments deep oceans. contain the world’s largest amounts of algal skeletons Sinking marine snow in the made of silica. Antarctic is primarily made up of algae and so it is an Geological oceanographers important source of organic who study ocean sediments, carbon and silica to the deep study the Antarctic sediments Antarctic waters and the and the algal skeletons in sediments. The silica is sediment cores they obtain contained in the tiny algal cell from the seafloor. The cores skeletons that are of intricate are often many, many feet long, shape and design. There is a and are collected with special very short season between equipment on oceanographic approximately late November research vessels. Sediments and February in the Antarctic and algae in the cores which (called the “austral spring and have been deposited over summer”) when every year millions and millions of years algae grow very rapidly due to are used by scientists to look at the high amount of sunlight at how the algae populations have this time and the supply of changed through time. Such important nutrients from changes are usually the result upwelling deeper waters. of changes in the ocean During this time of rapid algal environment where the algae growth, which we call a lived and are caused by climate “bloom”, large amounts of variations affecting the water marine snow containing algae temperature, circulation are formed and sink rapidly patterns, and nutrient levels. through the ocean. In addition,

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The Greenhouse Effect

The greenhouse effect is a areas and cities. Another effect condition that causes the is a change in weather average global temperature to patterns. rise over a period of time. Carbon dioxide and methane, The increase in CFC's in the air two gases in the atmosphere, also causes a thinning of the absorb heat as it radiates from ozone layer in the air. This the Earth's surface. They act ultimately affects marine life in like the glass in the Antarctica. With less ozone in greenhouse, not allowing the the atmosphere, more outgoing heat to radiate back ultraviolet radiation reaches the out into space, thus the term Earth. Higher ultraviolet may "greenhouse effect". With have damaging effects on the modern industry, we have put ability of phytoplankton to grow new greenhouse gases into the in the Antarctic surface waters. atmosphere, nitrous oxide and If so, there may be less food chlorofluorocarbon. These (algea) for the krill to feed on. gases come from sources such Less food for the krill means as car exhaust and aerosol less krill; less krill means that sprays. As the amount of the Antarctic animals that feed greenhouse gas increases, the on and survive on krill will Earth's temperature will rise. If suffer. Because it is so cold in that happens, some polar ice Antarctica, the ozone thins out can melt and there will be a rise even more than elsewhere on in sea level, flooding coastal the globe.

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Activity 2-1 Classroom Discussion

1. Describe the experience of Calving by imagining what you would see, hear and feel. 2. What effect would Polar melting have on other continents? (If the Antarctic ice were to melt, the sea would rise almost 200 feet.) 3. For what reasons would Amundsen leave his supplies at the South Pole for Scott? 4. Is Marine Snow really "snow"? (No. Marine snow is the debris or dust that falls through the oceans and settles on the sea floor. Marine snow helps transport material from the surface ocean to the deeper layers of the sea.)

Student Information Sheet 2. Antarctica II: Component I Ice/Glaciers Component II Marine Snow

Ice/Glaciers

Antarctica's cold, thick hard Transantarctic Mountains covering, called an ice sheet, divide the areas of the began to form 25 million years continent known as West and ago. Approximately 98% of East Antarctica. Antarctica is covered by ice. Antarctica actually changes size – during the summer A glacier is a huge mass of ice, months (October-March), the formed from compacted snow, coastal ice melts and Antarctica whose sides are often bounded "shrinks." by mountains or the walls of a valley. Ice sheets, or caps, Although almost all of which are also formed from Antarctica's land mass is compacted snow, are so covered by ice, in a few places massive that they cover entire on the continent, mountain landscapes, mountains as well peaks poke through. The as valleys. What is Marine Snow?

Marine snow is the debris or helps helps transport material dust that falls through the from the surface ocean to the oceans and settles on the sea deeper layers of the sea. floor, the same way as dust in Scientists believe marine snow the air settles on an object in is a major food source for life in your home. The difference is the abyssal deep, Marine snow that this ocean dust is full of plays an important ecological nutrients and life. Marine snow role by moving atmospheric

©PROJECT OCEANOGRAPHY STUDENT INFORMATION SHEETS 2 105 ANTARCTIC carbon from the surface of the formation of the debris that oceans to the seafloor. This sinks through the ocean in can affect the climate over marine snow. Some small thousands of years by percentage of the total carbon removing carbon from the remains at the bottom of the atmosphere and transporting it ocean as marine snow and is to the deep sea. Atmospheric largely consumed by benthic carbon dioxide dissolves in the (bottom dwelling) organisms. ocean water, and algae take up This percentage can be as high the gas as they as ten percent of the total photosynthesize, converting the carbon in coastal waters and atmospheric carbon into plant less than one percent in the carbon as the algae grow. The deep oceans. algae contribute to the Greenhouse Effect

The greenhouse effect is a new greenhouse gases into the condition that causes the atmosphere, nitrous oxide and average global temperature to chlorofluorocarbon. These rise over a period of time. gases come from sources such Carbon dioxide and methane, as car exhaust and aerosol two gases in the atmosphere, sprays. As the amount of absorb heat as it radiates from greenhouse gas increases, the the Earth's surface. They act Earth's temperature will rise. If like the glass in the that happens, some polar ice greenhouse, not allowing the can melt and there will be a rise outgoing heat to radiate back in sea level, flooding coastal out into space, thus the term areas and cities. Another effect "greenhouse effect". With is a change in weather modern industry, we have put patterns.