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A-level section teachers' notes

Ice Land and Sea

1.1 Key physical features

Question 1 is designed to familiarise students with the general geography of Antarctica and surrounding seas, including the primary regions, islands, topographical features, and geographical reference points. The weblinks allow students to search for more information and introduce students to satellite imagery (remote sensing) through browsing the 'Lima' website (Landsat Image Mosaic of Antarctica).

Questions 2 and 3 are for students to practice their map skills (elevation, scale, distances). (The ice surface is highest in central East Antarctica, at Dome Argus or 'Dome A'.) (The nearest distance from the Peninsula to South America is just over 1000km.)

Questions 4 and 5 are for students to become familiar with the distances represented by degrees of latitude. The conversions are as follows: 1 degree of latitude contains 60 minutes, a minute of latitude is a nautical mile, 1 nautical mile is 1.852km. The latitude of the coastline at 90°W is approximately 72.5°S and at 90°E is approximately the Antarctic Circle (66.5°S). The difference in latitude is about 41° (so 2460 minutes or nautical miles) which is 4556km. The latitude of London is approximately 51.5°N and the latitude of the edge of the Fimbull Ice Shelf on the Prime Meridian is approximately 70°S. The difference in latitude is 121.5° which is about 13 500km.

1.2 Tectonic history: into the deep freeze

Question 1 is designed to familiarise students with the main divisions of geological time from the break up of Pangaea onwards and with the changes that occurred in Antarctica over this time frame. The link to the British Geological Survey website can be used in conjunction with the 'Cold facts' text (and the additional weblinks) to complete the time line.

Question 2 focuses on the most recent geological period (the Quaternary Period) which is also referred to as the 'Ice Age'. The Quaternary Period itself is divided into the Pleistocene Epoch and the Holocene Epoch. The Pleistocene extends from 2.6 myr ago up until the present warm phase (the Holocene interglacial) that started 11 700 years ago and continues at present. (Note that some older sources quote the Pleistocene as starting 1.8 myr ago and the Holocene as starting 10 000 years ago.)

Students should achieve a basic understanding of the idea that the planet has been relatively cold during the Quaternary Period; but that there have been large fluctuations in the amount and extent of glacier ice. Question 2b is concerned with the idea that these fluctuations have been larger in the Northern Hemisphere: although the size and thickness of the Antarctic ice sheets also varied in step with the glacial/interglacial cycles, the presence of the Southern Ocean limits how far Antarctic glaciers can expand. Northern Hemisphere ice sheets could grow and expand to much lower latitudes during glacial times because of the presence of a lot of land at mid-latitudes in the Northern Hemisphere; whereas in the Southern Hemisphere the mid-latitudes are mostly ocean.

1.3 Antarctica's geology

Question 1 focuses on Mount Erebus as a case-study of an active volcano. Through writing a briefing paper (or compiling a fact file) using the weblinks provided, students will gain an understanding of the physical nature of Mount Erebus and its tectonic setting. Even though it is specific to Antarctica, this exercise, and the associated websites, can be used more generally for the study of tectonics and tectonic hazards.

1.4 Ice sheets and glaciation

Question 1 requires students to identify the main areas of ice within and around Antarctica as well as some of the most well known glaciers. By using the suggested weblinks, students will gain experience with satellite imagery (the 'Lima' website) and of the storage and retrieval of data in a GIS (Geographical Information Systems) programme (the gisdata link produced by the USGS).

Question 2 is another skills activity focusing on interpretation of an aerial photograph. From the photo, students should be able to identify the classic features of glaciation listed, as well as the area of calving where the glacier meets the sea and the icebergs that have detached from the glacier. The flow directions of the glacier are fairly clear, and the areas with crevasses indicate where ice flow speeds up (causing extension of the ice mass). These areas of faster flow occur both where slope gradient increases, and where the glacier reaches the sea and becomes floated.

The answer to Question 3a is that glacier flow varies across a glacier, so more than one area of crevasses needs to be tracked to give a realistic average value for ice velocity. For Question 3b, crevasse tracking by satellites enables a much greater area to be analysed than is possible by ground-based surveying (which is both time consuming and costly).

Question 3c requires basic skills with Excel and gives students the opportunity to revise descriptive statistics (e.g. central tendency and variance) and to manipulate and interpret some real data for an Antarctic glacier (the Byrd Glacier). The arithmetic mean ice velocity for the surface of the glacier is 634m per year and the average compass bearing for the direction of flow is 63°. The maximum ice velocity is 875m per year and the minimum is 7m per year. The range is 868 and the standard deviation is 233. The main reasons for variation in the surface velocity across the Byrd Glacier relate to friction along the sides and bed of the glacier and slope gradient. By clicking on the weblink with the isoline map of ice velocity, students will see that ice flow is fastest near the centre of the glacier.

Question 4 builds upon the previous question by asking students to think about a research problem that would require evaluation of similar data. The hypothesis is that the disintegration of ice shelves leads to an increase in the flow velocity of the glaciers that were formerly buttressed by the ice shelves. The knock-on effect is that glacier ice would be discharged into the ocean more rapidly, causing the mass balance of glaciers to become negative thereby contributing to sea level rise. Students should be aware that testing this hypothesis requires comparison of similar glaciers in similar settings – at least one that is buttressed by an ice shelf and another that no longer has an ice shelf. By crevasse tracking and ground surveying, ice velocities across the surface of each glacier could be compiled, and the mean velocities and ranges for the two glaciers could be compared. If there is overlap between the range of velocity values for each glacier, then an 'inferential' statistical test may be required to decide if there is a significant difference between the two sets of velocity readings. (In other words to decide whether or not the hypothesis of difference can be supported at a statistically significant level.) A-level geography students should be familiar with the Mann-Whitney U Test, which is a test of 'difference between samples' using ranked values; however, the Student T-test (also a test of difference) would be more suitable for comparing such large data sets.

1.5 The coast and adjacent seas

Questions 1 and 2 ask students to make use of the suggested websites to identify and locate Antarctica's major ice shelves. Major ice shelves for the continent as a whole (Q. 1) include the Ross, Ronne-Filchner, Rilser-Larsen, Fimbul, Amery, and Shackleton ice shelves. For the Peninsula (Q. 2) ice shelves located should include Larsen C, Wordie, Wilkins, and George VI, as well as the former locations of Larsen A and Larsen B.

Question 3 requires basic skills with Excel giving students the opportunity to analyse data on changes in the area of Peninsula ice shelves. The percentage of the original area remaining for the George VI (north) ice shelf is obtained by typing in the formula: =(c7/b7)*100 into a cell in row 7 of a new column, and the percentages remaining for the other ice shelves are obtained by simply dragging this formula down the rest of the column. The total area lost between the periods of measurement is 27 207km2. The graph should be a simple bar chart that shows the percentage area remaining for each Peninsula ice shelf, and this can be drawn on Excel using the chart wizard or by hand with graph paper. The bars for each ice shelf should be shown in order of the ice shelf's latitude along the Peninsula (from more northerly to southerly) as follows: Prince Gustav, Larsen A, Larsen B, Müller, Jones, Larsen C, Wordie, George VI (north), Wilkins. The graph shows that the most northerly ice shelves have experienced the greatest decline in area (Q.3b); although students should also note that the trend is not perfect (e.g. the Wordie Ice Shelf has lost more area than Larsen C).

Question 3c requires students to evaluate and explain the evidence shown in the graph, drawing upon information in the text and any relevant websites. The key ideas are that the limit of viability for Peninsula ice shelves is retreating southwards due to climate warming, and that this trend is likely to continue. Ice shelves such as Wordie, Larsen C, and Wilkins are looking increasingly vulnerable.

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