Kasi Wilson - [Updated F23] MEA100 Lab 09 Meltdown
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MEA100 Lab 9: Meltdown - The Cryosphere and Sea-Level Rise
Instructions: This file provided to you through the Google Assignment for this lab is your personalized copy. You do NOT need to make copies, change sharing settings, or create any other file - just edit this file directly and click submit in the Google Assignment.
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After reviewing the background material on Moodle and completing the pre-
lab questions, complete the lab below. Fill in your answers in the blue boxes provided in this document.
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You are encouraged to collaborate with your peers and to seek help/feedback from your TA as you work through the lab.
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To submit your completed lab, open the Google Assignment in Moodle and click the blue button that says “Open in Assignments.” Then click the blue button labeled “Submit.” Again you do not need to create or add any additional files. You must follow these instructions and submit your lab or we will not be able to provide feedback on it.
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Help us improve the lab by keeping track of approximately how long it took you to complete, how you interacted with your peers and/or instructor, and anything else you’d like to let us know about your experience with this lab by
completing a few short questions at the end of the lab
.
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Optional: Hone key skills from the Earth Scientist’s Toolbox even more by completing the optional extension
to the lab to earn badges demonstrating further course engagement and learning.
Introduction
The Earth's surface contains many forms of snow and ice, including sea ice, lake and river ice, snow cover, glaciers, ice caps and sheets, and frozen ground. Together, these features are known as the cryosphere. Although concentrated in the Polar Regions, parts of the cryosphere can be found at nearly all latitudes, which make them useful indicators of global climate and climate change. Different parts of the cryosphere change on different timescales ranging from less than a day to more than a millennium, as shown in the figure below [1]. 1
Fig. 1 Components of the Cryosphere and their time scales. Source: IPCC Fourth Assessment Report: Climate Change 2007, Figure 4.1 [1].
Outcomes:
In this lab you will:
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Describe changes in Arctic sea ice extent over time and space from satellite observations.
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Download data from a scientific database, and plot data to make predictions about future sea ice loss.
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Calculate changes in sea level due to observed melting of ice. ●
Apply systems thinking to identify effects of melting sea ice and land ice. Skills:
This lab makes use of the following tools from our “Earth Scientist’s Toolbox”: Change over time: Quantitative Literacy:
Time series, rates, prediction
Scatter plots
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Part I. Sea ice
In the first part of this lab, we will investigate changes in Arctic sea ice over the past 40+ years by observing satellite-based measurements of sea ice extent.
A. Seasonal changes in sea ice extent
First you will examine maps of average monthly sea ice extent in the Northern hemisphere for each month of two years: (1) last year, and (2) the year you were born. (If you were born before 1979 or simply prefer to choose another year, you may choose any year at least 10 years in the past.) Access the data in this folder containing maps of sea ice extent
, downloaded from the National Snow and Ice Data Center's data archives
[2]
. To find the years and months you are looking for, look at the file names, which indicate the year and month the image corresponds to: for example, N_197811_extn_blmrbl_hires_v3.0 copy.png
is an image of the extent of Northern he
misphere sea ice in November
of 1978
, as indicated by the prefix N
_
1978
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. 1.
Note which years you looked at and when the maximum and minimum areas of ice appeared to occur. What were the minimum and maximum extent of Arctic sea ice each year, and during which months did the minimum and maximum extent occur?
“Birth year” or other chosen year
Last year
Year
2003
2022
Month with maximum area of sea ice
February
February/March
Maximum sea ice extent (sq km) that year
15.2 million sq km
14.6 million sq km
Month with minimum area of sea ice
September
September
Minimum sea ice extent
(sq km) that year
6.1 million sq km
4.9 million sq km
2.
In what ways were the patterns of changes in sea ice extent over the course of the year last year similar to those in the year you were born? In what ways 3
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were they different? (e.g., Did the sea ice always form in the same locations? Did the minimum and maximum sea ice extents for the year occur at the same time of year? Was the area of ice in each of those years approximately the same for the same month? If not, how were they different?)
The minimum and maximum sea ice extent for each year occurred at the same time of year. Overall the area of the ice was greater in 2003 than it was in 2022 by about 1 million sq km.
B. Annual changes in minimum sea ice extent
We will now investigate how the annual minimum extent of Arctic sea ice has varied over the course of the full satellite record.
Tabulated monthly averages of sea ice extent (in million sq km) can be downloaded from the National Snow and Ice Data Center's data archives
[2]
. We have downloaded this data ahead of time for you. Files for each month can be found in the following “Monthly Sea Ice Extent and Area Data Files 1979-Present” folder
.
Each data file lists the average sea ice extent for a particular month, for each year from 1979 to the present. For example, the file “N_
01_extent_v3.0” shows the average sea ice extent in the northern hemisphere each January from 1979 to this year. Based on the month in which you observed the Northern Hemisphere sea ice extent to be at a minimum in question 1, the appropriate file to compare how the annual minimum sea ice extent has changed since satellite measurement of sea ice began in 1979.
3.
After selecting the appropriate file for annual minimum sea ice extent, create your own copy of the file or download the file. Create a plot showing minimum sea ice extent* vs. time in years, and add a trend line to your plot. Make sure your plot includes a title and clearly labeled axes. Once finished, 4
right-click on your plot, Copy it, and Paste it in the box below.
*If you’re curious why there are two columns in the data sheet you downloaded, one labeled “extent” and one labeled “area”, the difference between ice extent and ice area is explained here: http://nsidc.org/arcticseaicenews/faq/#area_extent
.
4.
(a) Use the plot you just made to predict when you would expect the Arctic Ocean to be ice-free for the first time (sea ice extent = 0). Describe how you made your prediction.
2080 because the sea ice goes down by 0.75 extent every 10 years.
(b) What factors might affect whether future sea ice extent matches your prediction?
The amount of pollution and greenhouse gasses, if they go up the sea ice extent might go down quicker, and if they go down the sea ice extent could
go down slower.
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Part II. Observing changes in land ice – ice sheets & glaciers
The GRACE twin satellites, launched 17 March 2002, were designed to make measurements of changes in Earth's gravity field. GRACE can be thought of as an accurate scale that can detect and quantify how the distribution of mass at Earth’s surface changes. The GRACE satellite data provides a detailed record of how the mass of large glaciers and ice sheets have changed over time—i.e., whether they are melting (losing mass) or growing (gaining mass). Monthly GRACE data for the Antarctic and Greenland ice sheets can be viewed on NASA’s Climate Change: Vital Signs of the Planet website
[3]. Table 1 below shows the average annual mass change of the Antarctic and Greenland ice sheets and smaller glaciers around the world. The ice sheet data is based on GRACE data from 2002 to 2017. The mass change data for smaller glaciers are based on a combination of GRACE data, satellite imagery, and local glaciological measurements for smaller glaciers and were published in Gardner et al. 2013 [4].
Table 1: Annual change in ice mass of glaciers and ice sheets
Location
Rate of ice mass change (Gt/year)
Glaciers - Alaska
-50
Glaciers - W. Canada/Contiguous U.S.
-14
Glaciers - Arctic Canada north
-33
Glaciers - Arctic Canada south
-27
Glaciers - Iceland
-10
Glaciers - Svalbard
-5
Glaciers - Scandinavia
-2
Glaciers - Russian Arctic
-11
Glaciers - Central Europe
-2
Glaciers - North Asia
-2
Glaciers - Caucasus and Middle East
-1
Glaciers - Himalayas
-26
Glaciers - Low latitudes
-4
Glaciers - Southern Andes
-29
Glaciers - New Zealand
0
All mountain glaciers (Total of all glaciers
listed above)
-216
Ice sheets - Antarctica
-127
Ice sheets - Greenland
-286
5.
Write out an equation to convert annual change in ice mass (in Gt/year) to 6
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rise in sea level (in mm/year). Be sure to include units! For reference: Density = mass / volume
Volume = depth x area
Density of water = 1 Gigaton (Gt) per cubic kilometer. Area of Earth surface covered by ocean = 360,000,000 square kilometers.
1 km = 1000 m
1 m = 1000 mm
(mass/360,000,000)x1,000,000
Hint: You are converting a mass to a volume of water and spreading that volume of water over the area of the entire ocean. You should not need to look up anything in addition to the information that has been provided. 6.
Calculate the average annual sea level rise in mm/year due to ice loss from mountain glaciers (total, you don’t have to calculate each one individually), Antarctic ice sheets, and Greenland ice sheets using your equation from the previous question, the data provided at the bottom of Table 1, and appropriate unit conversions.
Source of ice loss
Annual equivalent sea level rise (mm/yr)
Mountain glaciers
0.6
Antarctic ice sheets
0.35
Greenland ice sheets
0.79
TOTAL (rate of sea level rise from mountain glaciers + ice sheets)
1.74
7.
Why didn’t we ask you to calculate sea level rise from melting sea
ice in the previous part of this lab?
If you’re not sure, try the following experiment: Fill a glass with water, add 3 or 4 free-floating
ice cubes, and mark the water level. Wait for the ice to melt...where is the water level now?
The water level stays the same because sea ice is already a part of the water.
8.
Inspect satellite observations of variations in global mean sea level since 7
1993: Sea Level | Vital Signs – Climate Change: Vital Signs of the Planet
[5]. How does this compare to the rate of sea level rise you calculated from melting ice? What accounts for the difference?
Sea level has gone up due to global warming which makes water expand therefore rising sea level.
Hint: Relates to a fundamental property of matter.
9.
Besides effects on sea level, how does melting of sea ice and land ice affect other parts of the earth system (geosphere, hydrosphere, atmosphere, biosphere, Earth’s energy balance)?
Melting land ice affects the biosphere on land by taking away habitats for animals from the Antarctic. Melting ice also affects the hydrosphere by adding more liquid water back into the system. Methane is stored in glaciers so when they melt it is released. The geosphere is affected because melting glaciers affects land mass.
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Help us improve the labs in this course by answering a few more questions in the following Google Form: MEA100 Lab 9 Feedback
Earth Scientist's Toolbox extra-credit extension activities on next page… (you can opt to do one or the other, both, or none at all)
Optional extra credit extensions: Earth Scientist's Toolbox Skills (you can do one or the other, both, or none at all)
Quantitative reasoning - Carbon Cycle & Climate Change Looking at the observed rate of sea level rise and observed rates of ice loss, from the activities above, calculate what fraction of observed sea level rise over the past couple decades is due to melting of land ice around the globe, and fill in the table below. ●
Copy the rate of sea level rise you calculated for mountain glaciers, Greenland ice sheets, and Antarctic ice sheets from your answer to question 6 from Part II. ●
Subtract the total contribution of glaciers and ice sheets from the observed rate of sea level rise noted in question 8 of Part II to calculate the contribution of other causes of sea level rise.
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Divide the rate of sea level rise due to melting of different ice sheets and glaciers by the overall rate of sea level rise to calculate the “fraction of rate of observed sea level rise”.
Source
Contribution to sea level rise
(mm/year)
Fraction of rate of observed sea level rise
Mountain glaciers
Greenland ice sheets
Antarctic ice sheets
Other causes of sea level rise
Now look at the table below to compare the total mass of ice stored in these different reservoirs, and calculate how much sea level rise would occur if each of
these melted entirely (using the same equation you used in Part II of the lab).
Location
Gigatons of ice present
Potential sea-level rise (m)
East Antarctic ice sheet
23,870,000
West Antarctic ice sheet
2,990,000
Antarctic Peninsula
208,000
Greenland
2,402,000
All other glaciers
165,000
Based on the information above, which parts of the cryosphere do you think present the most cause for concern in a warming world and why? (There is no single correct answer; just explain your reasoning.)
Spatial Reasoning - Carbon Cycle & Climate Change
How much of the ice sheets ultimately melt will depend on how much warming occurs due to burning fossil fuels. Even though the equilibrium amount of melting (and associated sea level rise) could take centuries to be reached, our carbon pollution choices this century will “lock in” the eventual 9
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amount of melting. For example, if all fossil fuel resources were to eventually be used, then almost all ice sheets on Earth would melt! (See your own calculation above to see just how much of a rise in sea level that would mean…) However, if rapid action is taken to drastically reduce emissions over the next decades, the locked-in long-term rise in global sea level could be as “little” as 1m from partial melting of the Greenland ice sheet plus 2m from partial melting of the Antarctic ice sheets.
Explore this interactive sea-level map
[6] that shows what areas would be below sea-level at different levels of sea-level rise. Choose two coastal areas on different continents and describe direct and indirect effects of possible future sea-level rise on these areas over the next few centuries. Paste appropriate screenshots of the map to support your reasoning.
References / Sources
[1] Lemke, P., J. Ren, R.B. Alley, I. Allison, J. Carrasco, G. Flato, Y. Fujii, G. Kaser, P. Mote, R.H. Thomas and T. Zhang (2007) Observations: Changes in Snow, Ice and Frozen Ground. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
[Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. https://archive.ipcc.ch/publications_and_data/ar4/wg1/en/figure-4-1.html
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[2] Fetterer, F., K. Knowles, W. N. Meier, M. Savoie, and A. K. Windnagel. 2017, updated daily. Sea Ice Index, Version 3
. Boulder, Colorado USA. NSIDC: National Snow and Ice Data Center. doi: https://doi.org/10.7265/N5K072F8
. Last accessed June 05, 2020.
[3] NASA. Ice Sheets | NASA Global Climate Change. Retrieved June 05, 2020 from
https://climate.nasa.gov/vital-signs/ice-sheets
[4] Gardner, A. S., Moholdt, G., Cogley, J. G., Wouters, B., Arendt, A. A., Wahr, J., . . . & Paul, F. (2013). A reconciled estimate of glacier contributions to sea level rise: 2003 to 2009.
Science, 340
(6134), 852-857. doi:10.1126/science.1234532
[5] NASA. Sea Level | NASA Global Climate Change. Retrieved June 05, 2020 from
https://climate.nasa.gov/vital-signs/sea-level/
[6] Climate Central. Coastal Risk Screening Tool. Retrieved October 31, 2021 from https://coastal.climatecentral.org/
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