Ice cores

Module: Ice Core Data

February 23, 2012, 11:55 pm
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SUMMARY

 

This is a data-driven module designed to address key questions about the stability of the Earth’s climate in the past and the factors that drive climate change. This information is essential for students who want to study current climate change using NASA data, and interprets this in a correct historical context.

 

This set of exercises focuses on data from ice cores and addresses questions such as:

 

·       Is the climate stable?

·       How has climate changed in the past?

·       How is the level of carbon dioxide in the atmosphere related to global temperature?

·       How has sea level changed in the past?

 

This module is based on real data, freely available online, but often difficult for inexperienced students to import and analyze. These data have been collected and presented in a format that allows students to make their own analyses and interpretations. Each exercise has two sections: The first a spreadsheet tab with original data; the second, a tab with graphs that students use to answer a set of related questions.

 

These original data are presented in the hope that students can be encouraged to make their own observations, formulate their own questions, construct their own plots, and reach their own conclusions about the nature of climate change. Faculty may decide to present students with the data first and use the graphs for later interpretation in class.

GOALS

 

Use data based on ocean and ice cores to investigate how sea level, global temperature and the level of atmospheric CO2 have changed over the last 170 million years

   

Identify how changes in these and other data over the last 2 million years can be related to the formation of polar ice sheets

CONTEXT FOR USE

Instructions

 

Open the spreadsheet (see below) and click on the tab for the first exercise. Each exercise has two tabs: one for the data, and a second with some graphical analysis to help you with your answer these questions.

 

Click here to download the Spreadsheet (Microsoft Excel)

Click here to download only the graphs (PDF)

 

Answers?:

Suggested answers to all exercises are available below.

 

Exercise One:

The Phanerozoic Record of Global Sea-Level Change

 

Aim: Use data based on ocean cores to investigate how sea level has changed over the last 170 million years and identify how changes over the last 2 million years can be related to the formation of ice sheets.

 

Learning Outcome: Students will understand that large changes in sea level are quite normal and natural, and that over the last 2 million years, pronounced cycles in sea level of over 100 m have occurred due to the growth and decay of continental ice sheets.

 

Added value: Teachers can encourage students to select data from specific intervals of time and investigate the rate of sea level change over this time. This also presents an opportunity to review the difference between eustatic sea level change and regional change.

This exercise uses data from ocean cores that have been used to estimate how much sea level in the past has changed relative to the current day.

 

For the following questions please look at graph number one; "The Phanerozoic Record of Global Sea-Level Change"

 

1.     Look at the data sheet for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

 

2.     Look at the frequency of change in the sea level curve

a.      Over what interval is the frequency highest?

b.     Over what interval is the frequency lowest?

c.      What is the reason for this difference?

 

3.     What is the general trend in sea level between 170 mya and 55 mya?

a.      Can you explain this trend?

 

4.     Look at the two major cycles that occur between 82 mya and 70 mya

a.      What is the duration of each cycle?

b.     What is the most likely reason for each cycle?

c.      Why is global glaciation not likely to be the answer?

 

5.     When does the maximum peak in sea level occur in this record?

a.      What happened in the geological record at this time?

b.     What was the most likely cause of sea level rise?

c.      Describe what happened to sea level after this pronounced maximum.

d.     What is the most likely cause of this change?

 

For the following questions please look at graph number two; "Estimated Global Sea Level" (0-6 mya)

 

This graph uses the same data as used in the exercise above.

 

1.     What time span does this expanded section of these same data cover?

 

2.     Describe what happens to average sea level over this interval.

 

3.     Look at how the amplitude of the sea level curve changes...

a.      What is the range between maximum and minimum from 6.2 mya to 3 mya?

b.     What is the range between 3 mya and 1 mya?

c.      What is the range between 1 mya and the start of the record?

d.     What do these changes in amplitude actually represent?

 

For following questions please look at graph number three; "Estimated Global Sea Level" (0-2 mya)

 

1.     What time span do these data cover?

 

2.     Look at the amplitude and frequency of this curve

 

3.     What happens to the frequency from around 1 mya to the start of the record?

 

4.     What happens to the amplitude of the signal over this same period?

 

5.     Can you explain the changes?

Exercise Two:

Changing Global Temperature

 

Aim: Investigate how δ18O data from the shells of foraminifera recovered from sediment cores can be used as a proxy for ocean temperature, and explore how both how ocean temperature and sea level have changed in step over the last 2 million years.

 

Learning Outcome: Students identify the close relationship between ocean temperature and sea level and understand how changes in ocean temperature reflect the growth and decay of ice sheets

 

Added value: Students are encouraged to use Sheet Ex_2 Data to convert the raw δ18O to temperature using the graph of δ18O vs. Temperature on Sheet Ex_3 Graphs.

 

This second exercise uses data from the combined record of a number of Ocean Drilling Project (ODP) cores. The first two graphs are the ODP data at different scales. The third graph is a copy of the sea level data from the first exercise for comparison.

 

For following questions please refer to the graph labeled “LR404 Global Pliocene-Pleistocene Benthic Stack”

L404 Benthic Stack

 

1.     Look at the data sheet for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

d.     What has been measured on the Y-Axis?

 

2.     What was the overall trend in sea level between 5.2 mya and around 3.4 mya?

 

3.     What happened to the overall trend in sea level between 3.4 mya and the youngest part of the record (towards the left hand side)?

 

For the following questions please refer to the second graph and third graphs labeled “LR404 Global Pliocene-Pleistocene Benthic Stack” and “Estimated Sea Level” (2 mya-present)

 

L404 Benthic Stack and Sea Level Data

 

1.     Compare the range in amplitude of these data records between 2 mya and the start of the record

 

2.     How does the temperature record compare with the sea level record?

 

3.     Do both records record the same changes?

 

4.     For both records, what is the average duration of each cycle before (older then) 1 mya?

 

5.     For both records, what is the average duration of each cycle between 0.8 mya and the present?

 

6.     For both records, compare the minimum range on the Y-axis both before and after 0.1 mya

 

7.     What does this change signify?

 

8.     Why is this change represented in both the isotope data from foraminifera and sea level record?

Exercise Three:

NGRIP Oxygen Isotopes

 

Aim: To explore how the climate in Greenland changed between the height of the last interglacial (Eemian) period and the present day.

 

Learning Outcome: Students learn that there are many short and medium term cycles superimposed on long term climate trends. They will contrast the amplitude, frequency, and rate of climate change over different intervals of time, and compare the rate of climate change to the changes we observe today.

 

Added value: Students with some knowledge of this period can identify Dansgaard Oeschger cycles and discuss their origin(s).

 

The NGRIP Greenland Ice Core (Oxygen isotope data δ18Ο)

 

This graph is based on data from the Northern Greenland Ice Core Project spanning an interval from 120,000 during the last Eemian interglacial period to the modern era. Be sure to locate this core on the map provided before starting the exercise.

 

Note: On this graph the data is younger towards the right hand side

 

1.     From the NGRIP Graphs tab on the spreadsheet determine;

a.      What is this graph measuring?

b.     How is this related to temperature?

 

2.     How would you describe the overall pattern of temperature change?

a.      Would you say that rapid climate change was unusual during this period?

b.     Which was most common: a rapid rise in temperature, or a rapid fall in temperature?

c.      How many major shifts in climate occurred over the last 60,000 years?

d.     What is the difference in δ18Ο between the warmest period during this interval and the coldest period?

 

3.     Using the graph provided, estimate the change in temperature this represents

 

4.     Look at the interval between 50,000 and 30,000 years ago. These are Dansgaard Oeschger cycles.

a.      What was the change in temperature on the ice sheet during this time?

 

5.     Estimate the change in temperature over the interval between 12,000 and 10,000 years ago

a.      What was the average rate of change per decade over this interval?

b.     How does this compare to the rate of change in temperature over the last 50 years?

 

6.     Are all the cycles you observe in this data of the same length?

a.      Is there a clear pattern to the cycles you see?

b.     How does the interval between these visible cycles match the internals of known Milankovitch cycles?

 

Exercise Four:

GISP2 Oxygen Isotopes

 

Aim: In this exercise students use temperature data derived from oxygen isotope data from the Greenland GISP2 core to investigate how the climate changed towards the end of the most recent glaciation.

 

Learning Outcome: Students identify Dansgaard Oeschger cycles, the Bölling Allerød and Younger Dryas events, the start of the current interglacial period, and investigate how the rate of climate change varied over these intervals.

 

Added value: Students can use the original data to calculate a first order derivative and plot the rate of climate change.

 

The GISP Greenland Ice Core

 

These data are from the Greenland Ice Sheet Project and focuses on the record of climate change at the end of the most recent glacial period. Be sure to locate this core on the map provided before starting the exercise.

 

Please refer to the first graph “Greenland GISP Core 2” (50 kya-0 kya) to answer this exercise

 

1.     What time interval do these data span?

 

2.     What is measured on the y-axis?

 

3.     How many Dansgaard Oeschger cycles can you identify in the interval between 50,000 and 10,000 years ago

 

4.     How does this compare to data from the NGRIP ice core?

 

5.     Use the original data from this ice core to estimate how rapidly the temperature rose at the start of the Bölling-Allerød event

 

6.     How long did it take the temperature to fall from the Bölling-Allerød maximum to the minimum of the Younger Dryas event?

 

The GISP Greenland Ice Core (II)

 

Please refer to the second graph “Greenland GISP Core 2” (15 kya-10 kya) to answer this exercise

 

This graph is taken from the same data as the last, but covers a much shorter interval during the end of the last glaciation.

 

1.     What was the average rate of warming over the interval 10,000 to 11,000 years ago?

 

2.     What was the maximum rate of warming over the interval 11,600 to 12,000 year ago?

 

3.     What was the average rate of cooling from 14,500 to 12,000 years ago?

 

4.     What was the maximum rate of cooling during this same interval?

 

The GISP Greenland Ice Core (III & IV)

 

Please refer to the third and fourth graphs “Greenland GISP Core 2” (0 kya-50 kya and 5 kya-15 kya) to answer this exercise (note the scale is reversed with younger data on the left hand side)

 

These graphs show the same data with a simple calculation of the rate of climate change superimposed in red.

 

1.     Look at the peaks and troughs that represent rapid climate change

a.      Which are most common: rapid rises in temperature of rapid falls in temperature?

b.     What is the maximum rate of temperature you observe?

c.      When did this occur?

 

2.     Look at the fourth graph on this page that plots these data over a shorter period of time.

a.      Compare the stability of climate before 11,000 years ago with the period from 11,000 to 3,000 years ago.

b.     What are the main differences you observe?

c.      How would you compare and contrast climate stability during glacial and interglacial periods?

Exercise Five:

NGRIP_GRIP and Dye_3

 

Aim: Students compare oxygen isotope data from three Greenland cores spanning the end of the last glacial period and the first 10,000 years of the current interglacial period.

 

Learning Outcome: Students observe both the Younger Dryas event and the 8,000 year cooling events, contrast the stability of the interglacial period with the climate record prior to 10,000 years, and compare cores the consistency of the ice records over thousands of years. Students should also identify the general cooling trend over Greenland that started around 8,000 years ago.

 

Added value: Students can discuss possible reasons for the periodic low amplitude oscillations in climate that punctuate the climate record over the last 10,000 years of relative climate stability.

 

The GRIP Greenland Ice Core

 

Please refer to the graphs “Greenland GRIP”, “GISP DYE-3” and “Greenland NGRIP” to answer this exercise

 

These data are from three ice cores from the Greenland Ice Cap. Be sure to locate these cores on the maps provided before starting the exercise.

 

1.     Look at the data sheet for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

 

2.     How well do the data agree?

 

3.     Can you find a record of the Younger Dryas event in these data?

 

4.     What happens to the record between 8,000 and 8,300 years ago?

a.      What change in temperature does this represent?

b.     What could be the reason for this temperature change?

c.      How does it compare to the Younger Dryas event?

 

5.     What is the general trend in climate on Greenland from 8,000 years ago to the present?

 

6.     How representative is this likely to be of the overall climate of the northern hemisphere?

 

7.     How representative is this likely to be of global climate?

Exercise Six:

GISP (Greenland) and Byrd (Antarctica) Isotopes

 

Aim: In this exercise students compare data from cores in Greenland and Antarctica to investigate how the timing of climate change varies in the Southern and Northern Hemispheres.

 

Learning Outcome: Students recognize that cooling in the Arctic was often accompanied by warming in the Antarctic (the bipolar seesaw) and that the Bölling Allerød and Younger Dryas events are not apparent in the Antarctic record.

 

Added value: Students can use this data to contrast the temperature record in both the Northern and Southern Hemispheres at the end of the last glaciation.

The GISP Greenland Ice Core and Byrd Antarctic Ice Core

 

These data are from cores on Greenland and Antarctica. Be sure to locate these cores on the maps provided before starting the exercise.

 

1.     Look at the data sheet for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

 

2.     How well do the records compare?

a.      Find one interval where these is close agreement

b.     Find one interval where there is little agreement

c.      How do the records compare between 70,000 and 40,000 years ago?

d.     What does this tell us about the link between the Arctic and Antarctic?

 

3.     Look at the data over the interval between 20,000 and 10,000 years ago

a.      Did warming occur at the same time at both sites?

b.     At which site did the greatest amount of warming occur?

c.      Find the record of the Younger Dryas event on the Greenland data

d.     Can you find any record of this event in Antarctica?

e.      Why should the record of warming be so different at both sites?

Exercise Seven:

Vostok Ice Cores (Antarctica)

 

Aim: This exercise investigates the relationship between temperature and carbon dioxide recorded in the Antarctic Vostok ice core.

 

Learning Outcome: Students observe the close relationship between CO2 and temperature and discuss the reason why changes in CO2 often lag behind changes in temperature.

 

Added value: Students can observe the approximately 100,000 year periodicity of glacial cycles over the last 400,000 years and discuss what factors could be responsible. They also compare the duration of interglacial periods the maximum temperatures recorded during these times.

The Vostok Antarctic Ice Core

 

These data are the Vostok core on Antarctica. Be sure to locate this core on the maps provided before starting the exercise.

 

1.     Examine the data sheet for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

 

2.     How many glacial and interglacial periods can you recognize from this data?

 

3.     How long has the present interglacial period lasted compared with previous interglacial periods?

 

4.     How well does the carbon dioxide record agree with the temperature record?

 

5.     Which tends to fall first: temperature or CO2?

 

6.     Which tends to increase first: temperature or CO2?

 

7.     Why should this happen?

Exercise Eight:

EPICA (Antarctica)

 

Aim: This exercise uses data from the EPICA ice core from Antarctica to investigate the relationship between solar insolation, temperature, carbon dioxide, sea level and wind intensity.

 

Learning Outcome: Students will:

·       Identify eight major climate cycles that have occurred over the last 800,000 years

 

·       Observe the close relationship between solar insolation and long-term climate change.

 

·       Observe that (like ocean temperatures during the year) global temperatures lag behind changing Milankovitch cycles

 

·       Identify changes in temperature and carbon dioxide that occurs during each cycle

 

·       Discover how changes in carbon dioxide often lag being changes in temperature

 

·       Contrast changes in sea level, temperature and the amount of dust in ice cores that occur over each cycle and be able to explain these in terms of glacial processes.

 

Added value: Students can measure the length of past interglacial periods and discuss how long it will be before we return to another cycle of glacial advance.

 

The EPICA Antarctic Ice Core

 

This data is from the EPICA Antarctic Ice core, the deepest to date. Be sure to locate this core on the map provided before starting the exercise. This chart is data intensive and my take some time to open on an older computer.

 

Please refer to the graphs “EPICA Milankovitch Insolation”, “Antarctica EPICA Temperature and CO2”, Antarctica EIPCA” and “Estimated Global Sea Level” to answer this exercise

 

1.     Look at the data sheets for this exercise.

a.      What is being measured?

b.     How is this determined?

c.      What time span do they cover?

 

2.     How many glacial and interglacial periods can you recognize from these data?

 

3.     How long has the present interglacial period lasted compared with previous interglacial periods?

 

4.     The first graph “EPICA Milankovitch Insolation”, is a measure of the amount of solar radiation arriving at 65°N of the equator as determined by Milankovitch orbital cycles.

a.      What is the overall pattern in these data?

b.     What is the periodicity of the major cycles you observe?

c.      How is the 100,000-year cycle represented on this data?

d.     How is the 42,000-year cycle represented on this data?

e.      Which Milankovitch cycle is most closely related to interglacial phases?

 

5.     Can you find a past pattern in the Milankovitch cycles that closely resembles recent changes?

a.      Find the interglacial period associated with this time

b.     How long does that interglacial last compared to the next three?

c.      What does that tell us about the probable length of the present interglacial period?

 

 

EPICA: Temperature and CO2

 

1.     Draw a series of lines from points where the temperature starts to increase rapidly to the Milankovitch data curve.

a.      Do rapid increases in temperature occur at the same time as more energy is reaching the northern hemisphere?

b.     Why is there a difference?

 

2.     How well do temperature and CO2 agree over this interval?

 

3.     Can you see any more examples of temperature leading changes in CO2? (Note: you may have to expand this data to look at some sections in more detail)

 

Dust in the ice cores

 

1.     Where does dust come from and how does it get into ice cores?

 

2.     Compare the dust record with the temperature record

a.      When is the record of dust at its greatest?

b.     Why should this be so?

 

Global Sea Level

 

1.     This data is an estimate of sea level using data from exercise one

a.      How well does the sea level curve follow the temperature curve

b.     Do closely do sea level maxima coincide

c.      Why would you expect a difference?

 

Suggested Answers

Click here to download the Ice Core Data Module as a PDF

Funded by NASA Global Climate Change Education Grant NNXO9AL64G.

Go to the NCSE-NASA Interdisciplinary Climate Change Education Homepage 

Glossary

Citation

Kitchen, D. (2012). Module: Ice Core Data. Retrieved from http://www.eoearth.org/view/teachingunit/51cbf1557896bb431f6a5245

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