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15.2: Assignment- Changes in Extent of Sea Ice at the Poles

  • Page ID
    6110
  • Module 15 Assignment

    Changes in Extent of Sea Ice at the Poles

    a15_scientists_full.jpg
    Figure 1. South African scientists work putting trackers on the ice in the Marginal Ice Zone of Antarctica on the Cape Agulhas II during a scientific cruise to the area in the winter of 2017

    Overview

    With regard to arguments supporting (or not supporting) climate change, climate scientists agree that climate change is happening and that it is indeed exacerbated by human activity. However, there are still a few skeptics and whole organizations outside of the field of climate science that are dedicated to debunking climate change. They might use real data to support their argument, but important data are often omitted or presented in such a way as to paint a very different or skewed picture of the evidence for or against climate change. In this lab activity, you will have an opportunity to explore and compare data presented from different points of view, including data presented in a widely circulated (but unattributed) article entitled “Antarctic Sea Ice for March 2010 Significantly Greater Than 1980,” which was published in April 2010 by a website called “Global Warming Hoax”. Feel free to visit the website and read the article before completing this lab, although it is not required.

    How to Draw a Best Fit Line

    All of the data provided in this lab originally come from the National Snow and Ice Data Center (NSIDC), housed at the University of Colorado, and can be freely downloaded at nsidc.org. You will be graphing these data and drawing a “best fit line” through the points in order to calculate the slope of line and examine trends in the data. An example of this process is shown below.

    a15_plot_full.png
    Figure 2.

    Instructions

    Part A – Original Data

    The two data points on sea ice extent that are included in the Figure 2 were obtained from the article “Antarctic Sea Ice for March 2010 Signicantly Greater Than 1980,” which was published on a website called “Global Warming Hoax.” The data, which is included to the left of the graph below, is the extent of Antarctic sea ice in millions of square kilometers as measured in March of 1980 and 2010. This data is accurate and is consistent with data that can be downloaded from NSIDC. To do this, follow the instructions on how to draw a best-fit line (above). In this case, steps two and three are the same and you can easily calculate slope using the original data.

    1. Based exclusively on the data provided and the graph, what conclusion would one make regarding climate change? Explain.
    2. Using the method illustrated in Figure 1, what is slope of the line of best fit for these two data points? Show all your work.
    3. Even though the above data are accurate, give and explain two reasons why this dataset might lead you to an incorrect conclusion regarding global climate change.
      1. Reason #1:
      2. Reason #2:
    a16_seaice_full.png
    Figure 3. Sea Ice Extent

    Part B – South Pole Sea Extent

    a15_antartica_full.png
    Figure 4. Map of Antarctica showing the extent of the polar ice cap and the extent of the floating ice shelves.

    In part B, you will explore an expanded dataset of Antarctic sea ice extent measured during March 1980 through 2018, downloaded from NSIDC. Only the even-numbered years are presented, but the addition of odd years does not alter the trend in the data. Following the instructions for how to draw a best-fit line (above), graph the data, draw a line of best fit, and calculate the slope of the line.

    Ice Extent – Southern Hemisphere
    Year Ice Extent, million square kilometeres
    1980 3.29
    1982 4.29
    1984 3.61
    1986 3.7
    1988 3.97
    1990 3.97
    1992 3.57
    1994 4.55
    1996 4.18
    1998 4.11
    2000 4.09
    2002 3.75
    2004 4.53
    2006 3.21
    2008 5.28
    2010 3.85
    2012 4.55
    2014 4.9
    2016 4.07
    2018 3.53
    a15_seaicesouth_full.png
    Figure 5. Sea ice extent in Southern Hemisphere measured in million square kilometers
    1. What is the slope of the line of best fit you estimated for this data set? Show all your work.
    2. What do these data tell you about how sea ice extent is changing in the southern hemisphere? How does your result for the extended dataset compare to the results from the data presented from the article presented in Part A?
    3. What can you say about the data variability, or how wide of a range the data points cover, between the earlier years and the later years on the graph?
    4. Please offer one suggestion for why the variability in sea ice extent has been changing between 1980 and 2018.

    Part C – North Pole Sea Ice Extent

    a15_greenland_full.png
    Figure 6. Map of Greenland showing the extent of the polar ice cap.

    Next, we will examine the ice-extent patterns of the northern Arctic polar ice sheet that is located on Greenland. The ice-extent data are from March 1980 through 2018 for even-numbered years, also downloaded from NSIDC. Again, here you will graph the data, draw a line of best fit, and calculate the slope of the line.

    Ice Extent – Northern Hemisphere
    Year Ice Extent, million square kilometeres
    1980 16.04
    1982 16.04
    1984 15.58
    1986 15.91
    1988 15.96
    1990 15.87
    1992 15.48
    1994 15.55
    1996 15.12
    1998 15.6
    2000 15.22
    2002 15.35
    2004 14.99
    2006 14.42
    2008 15.18
    2010 15.14
    2012 15.2
    2014 14.76
    2016 14.4
    2018 14.3
    a15_iceextentnorth_full.png
    Figure 7. Sea ice extent in Northern Hemisphere measured in million square kilometers
    1. What is the slope of the line of best fit you estimated for this data set? Show all your work.
    2. What do these data tell you about how sea ice extent is changing in the northern hemisphere? How does your result for the North Pole compare to that of the South Pole (Part B)?
    3. Explain why you might see a different trend, or slope of the best-fit line, when comparing the sea-ice extent data between the northern and southern hemispheres.