Students will construct graphs of the extent of sea ice over time.
Students will use technology to analyze data and draw conclusions about natural phenomena in the Antarctic
Students will compare the graphs and charts of the extent of sea ice over time between Antarctic and the Arctic
Students will explain the factors that affect Antarctica’s climate
Background Information Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves fringe lands in Earth’s polar regions. Glaciers and larger ice sheets move slowly over land in polar regions. Glaciers are also found on high mountaintops around the world. The soils of polar regions, called permafrost, are filled with frozen water. Together, these different types of frozen water are known as the Earth’s cryosphere. Approximately three-quarters of the world’s fresh water is frozen in the cryosphere.
Some parts of the cryosphere, such as snow and the ice on ponds and lakes in mid-latitude locations, are only around during winter months. Other parts of the cryosphere, such as glaciers and ice sheets, stay frozen year-round and, in fact, can stay that way for tens of thousands or even hundreds of thousands of years. Some of the ice in the ice sheet that covers most of the continent of Antarctica has been there for nearly a million years.
Sea ice is frozen seawater. It can be several meters thick and it moves over time. Although the salts in the seawater do not freeze, pockets of concentrated salty water become trapped in the sea ice when it first forms. The pockets of salty water can work their way out of the sea ice over a few years. During the summer months much of the sea ice melts and during the winter months it forms again. Some sea ice stays around all year long.
The Arctic Ocean has a large amount of sea ice floating at its surface, especially in winter. Sea ice is very important for the people and animals that live in the Arctic region. Animals like polar bears live on the sea ice and find their food in the surrounding and underlying ocean. Marine life exists under the Arctic sea ice too. Over the past few decades, more and more of the sea ice has been melting in the summer as Earth’s climate warms. Scientists predict that with continued rates of global warming there will be no sea ice in the Arctic in the summer months by the end of the 21st century. Ice thickness has also been decreasing.
In the South Polar Region, there is evidence that sea ice is important for the breeding cycle of certain penguin species. Emperor penguins breed on sea ice. One of the most northerly colonies of Emperor penguins, the one where the documentary “March of the Penguins” was filmed, has declined over the past few decades, probably because of warming temperatures, which cause the sea ice to melt and break apart earlier in the spring, before the chicks are ready to fledge. Melting sea ice might have some benefit to Adelie penguins. Adelie penguins build nests made of pebbles on land. In search of food, they travel over sea ice that is attached to the shore, called fast ice, to get to the ocean, and then bring seafood back to their hungry chicks on land. With less sea ice, the journey to the ocean to find food becomes shorter. However, Adelie penguins are adapted to the cold conditions. The benefit of a shorter trip to the ocean is overshadowed by the harm of warmer temperatures. In the northern part of the Antarctic Peninsula, the warmest part of Earth’s coldest continent, the Adelie penguin colony is declining rapidly. In this area sea ice used to be common, but now is absent even in winter. The penguin nests made of rocks on the Antarctic Peninsula have been abandoned. The warming climate has restricted the Adelie penguins to colder areas further south.
A rise in sea levels is one of the most well-known consequences of global warming. There are two ways that higher temperatures cause higher sea level: (1) melting ice sheets and glaciers and (2) thermal expansion of seawater. How much is sea level rising? Since 1900, sea level has risen between 1 and 2 millimeters per year (10-20 cm or 3.9-7.9 inches per century) on average. During the preceding 3,000 years, scientists estimate that sea level was almost constant, rising at a rate of 0.1 to 0.2 mm per year.
Scientists use averages from a large number of tide gauges around the globe to estimate global average sea level. Since 1992, global sea level has been observed using satellite data too, with more accurate results than tide gauges (according to the Intergovermental Panel on Climate Change AR4 report). Satellite measurements show a rate of sea level rise of 3 mm per year, far more than the tide gauges. Some scientists suspect that the satellite is incorrectly calibrated. Others suspect that the difference may be because the satellite measurements cover much of the globe while tide gauges are near coastlines.
Change in global sea level in the future is predicted to occur at a faster rate. The amount of sea level rise depends in large part on the amount of warming. According to the IPCC Forth Assessment Report (2007) by the mid-2090s global sea level may be 22 to 44 centimeters above its 1990 level and rising at about 4 mm per year.
Sea Level Rise Due to Melting Ice Sheets and Glaciers There is between 24 and 30 million cubic km of ice on land. About 90% of this ice is in Antarctica. Most of the rest is in Greenland and a tiny fraction is locked up in mountain glaciers elsewhere.
As global temperatures have risen, some of this ice has begun to melt. And as ice melts, meltwater flows into the ocean, gradually raising sea level. Of course, each year the amount of ice on land changes with the seasons, but overall global warming has begun to disturb this equilibrium. Melting has outpaced snowfall, and the loss of ice has been greatest on mountain glaciers in the mid-latitudes and tropics and on the Greenland ice sheet. The Antarctic ice sheet seems less disturbed, however there’s evidence that the rate of ice flowing towards the ocean has increased.
Melting ice can produce a positive feedback loop - darker areas (especially oceans, but also land) beneath the high-albedo snow or ice absorb more light than the bright snow or ice had done, and thus warm still further, melting more snow and ice. This will be further discussed in the next week of the course.
Melting ice can alter the salinity of seawater as freshwater is added to the ocean. Changes in salinity alter seawater density, which can change major ocean currents that transport heat through the ocean driven by the currents, stimulating more climate change.
Complete melting of glaciers and ice sheets would raise sea levels worldwide almost 70 meters (230 feet) above current levels. 7.2 meters of this rise would be from the Greenland ice sheet, while 61.1 meters of this rise would be from the Antarctic ice sheet. Melting glaciers would add another half of a meter.
For some perspective on all this melting ice, consider this: sea level has risen about 120 meters since the last glacial maximum approximately 20,000 years ago when ice covered large parts of the Northern Hemisphere and wooly mammoths roamed the Earth.
New York State
STANDARD 1—Analysis, Inquiry, and Design
Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose ques- tions, seek answers, and develop solutions.
Students will access, generate, process, and transfer information, using appropriate technologies.
2.1b The transfer of heat energy within the atmosphere, the hydrosphere, and Earth’s interior results in the formation of regions of different densities. These density differences result in motion.
2.1i Seasonal changes can be explained using concepts of density and heat energy. These changes include the shifting of global temperature zones, the shifting of planetary wind and ocean current patterns, the occurrence of monsoons, hurricanes, flooding, and severe weather.
2.2c A location’s climate is influenced by latitude, proximity to large bodies of water, ocean currents, prevailing winds, vegetative cover, elevation, and mountain ranges.
Hypothesis – What is the relationship between the extent of sea ice and time in years for Antacrtica?