I Would Like the Students to Retrieve and Clean the Data, So That They Can See That This

Mentor Session 3

Objective:

Students will:

· download ice core data from Greenland

· clean and import the data into Excel

· develop a graph

· analyze these data using the graph

An ice core is a core sample from glaciers. Ice and snow re-crystallize and trap air molecules from previous time periods. Scientists analyze the Ice cores and the trapped gasses, especially measuring the presence of hydrogen and oxygen isotopes. The gasses’ composition provides a picture of the climate at the time they were trapped. (Information about atoms and isotopes can be found at the end of this lesson.)

Because water molecules containing heavier isotopes exhibit a lower vapor pressure, when the temperature falls, the heavier water molecules will condense faster than the normal water molecules. The relative concentrations of the heavier isotopes in the condensate indicate the temperature of condensation at the time, allowing for ice cores to be used in local temperature reconstruction after certain assumptions. In addition to the isotope concentration, the air bubbles trapped in the ice cores allow for measurement of the atmospheric concentrations of trace gases, including greenhouse gases carbon dioxide, methane, and nitrous oxide.

Read:

George H. Denton, Richard B. Alley, Gary C. Comer, Wallace S. Broecker (2005) The role of seasonality in abrupt climate change. Quaternary Science Reviews, Volume 24, Issues 10-11, Pages 1159-1182

You will be accessing archived data from research on the Greenland Glaciers. The ice cores were archived by:

Alley, R.B. 2004. GISP2 Ice Core Temperature and Accumulation Data. IGBP PAGES/World Data Center for Paleoclimatology Data Contribution Series #2004-013. NOAA/NGDC Paleoclimatology Program, Boulder CO, USA.

These are raw data. In order to analyze them, you will need to “clean” the data. That means you will prepare it in a format that can then be analyzed by a variety of different statistical programs, or, as in our case, used to build graphs.

Directions to the students:

· Open http://www.ncdc.noaa.gov/paleo/icecore.html. This is the site that scientists use to archive their data.

· Under the menu “Obtain Data” select the first choice, “Ice Core Data Search, pull-down menus” (http://hurricane.ncdc.noaa.gov/pls/paleo/fm_createpages.icecore).

Your page should look like this:

Select “Greenland” in Countries and hit “Start Search.”

Be sure that “Variable” and “Investigator” are set on “All.” In the example above, “Variable” is set to CO2. That needs to be changed to “All.”

This will get you to the data set page. You can search on “Temperature.”

That will get you to the correct data set, Temperature Reconstruction and Accumulation Data (Alley, R.B.). Open that file.

Select all (control A on PC) and copy. Open Word and paste the entire file into Word.

From Word, go to #2. Accumulation rate in central Greenland (on my document, starts on page 30). Highlight and scroll down to the end of the document. Delete these data. (We are not analyzing the accumulation rate, only the temperature reconstruction.)

2. Accumulation rate in central Greenland

Column 1: Age (thousand years before present)

Column 2: Accumulation rate (m. ice/year)

Age Accumulation

0.144043 0.244106

You will have this Temperature Reconstruction data remaining (and these are the data we are using, and I have it following the directions). To import into Excel, it is easiest to select on column at a time. Place the cursor several spaces before the word “Age”, press the “ALT” key, and keep that pressed as you highlight just the column and all the digits of the data. When you reach the end of the last page, copy the data, and paste it into Excel. You will have a total of 1632 lines of data, plus the heading of “Age.” Repeat for “Temperature.”

In Excel, you will want to build scatterplot graphs. The x axis is “Thousands of Years,” and the y axis is “Temperature.” That example is in the attached Excel file. Be sure students label their axes, and give the graph a good name.

In their paragraph about the data, be sure that they only talk about the data, and not to draw any conclusions. They must use words like The Ice Core Data of Reconstructed Temperature from (name of location) and then describe the graph. Be sure that they cite Alley. They can copy the citation directly from the data.

GISP2 Ice Core Temperature and Accumulation Data

---------------------------------------------------------------------

NOAA Paleoclimatology Program

and

World Data Center for Paleoclimatology, Boulder

---------------------------------------------------------------------

NOTE: PLEASE CITE ORIGINAL REFERENCE WHEN USING THIS DATA!!!!!

NAME OF DATA SET: GISP2 Ice Core Temperature and Accumulation Data

LAST UPDATE: 3/2004 (Original Receipt by WDC Paleo)

CONTRIBUTOR: Richard Alley, Pennsylvania State University.

IGBP PAGES/WDCA CONTRIBUTION SERIES NUMBER: 2004-013

SUGGESTED DATA CITATION:

ORIGINAL REFERENCE: Alley, R.B. 2000. The Younger Dryas cold interval as viewed from central Greenland. Quaternary Science Reviews 19:213-226.

ADDITIONAL REFERENCE:

Cuffey, K.M., and G.D. Clow. 1997. Temperature, accumulation, and ice sheetelevation in central Greenland through the last deglacial transition. Journal of Geophysical Research 102:26383-26396.

GEOGRAPHIC REGION: Greenland

PERIOD OF RECORD: 49 KYrBP - present

DESCRIPTION:

Temperature interpretation based on stable isotope analysis, and ice accumulation data, from the GISP2 ice core, central Greenland. Data are smoothed from original measurements published by Cuffey and Clow (1997), as presented in Figure 1 of Alley (2000).

ABSTRACT:

Greenland ice-core records provide an exceptionally clear picture of many aspects of abrupt climate changes, and particularly of those associated with the Younger Dryas event, as reviewed here. Well-preserved annual layers can be counted confidently, with only 1% errors for the age of the end of the Younger Dryas 11,500 years before present. Ice-flow corrections allow reconstruction of snow accumulation rates over tens of thousands of years with little additional uncertainty. Glaciochemical and particulate data record atmospheric-loading changes with little uncertainty introduced by changes in snow accumulation. Confident paleothermometry is provided by site-specific calibrations using ice-isotopic ratios, borehole temperatures, and gas-isotopic ratios. Near-simultaneous changes in ice-core paleoclimatic indicators of local, regional, and more-widespread climate conditions demonstrate that much of the Earth experienced abrupt climate changes synchronous with Greenland within thirty years or less. Post-Younger Dryas changes have not duplicated the size, extent and rapidity of these paleoclimatic changes.

DATA:

1. Temperature in central Greenland

Column 1: Age (thousand years before present)

Column 2: Temperature in central Greenland (degrees C)

Age Temperature (C)

0.0951409 -31.5913

0.10713 -31.622

0.113149 -31.6026

0.119205 -31.6002

0.119205 -31.598

0.125451 -31.6656

0.132407 -31.7235

0.138807 -31.7583

0.145126 -31.8098

0.152263 -31.8415

0.152263 -31.8813

0.15938 -31.9559

0.165464 -32.0241

0.171847 -32.038

0.179421 -31.9872

0.186623 -31.9689

Atoms and Isotopes:

The smallest discrete piece of matter is an atom. An atom is made up of particles including protons, neutrons (that form the nucleus), and electrons (that swarm around the nucleus in a cloud, although they are pictured as if they orbit in a plane). The nucleus is more than 99.9% of the atom’s mass, and the electron’s mass is so small, it is not included when calculating the total mass of atoms. The atomic number of the atom is the number of protons, but the weight of the atom is the total number of protons plus the total number of neutrons. In the example below, there are 2 protons, 2 neutrons, and 2 electrons in the helium atom. The atomic number of helium is 2 and the atomic mass is 4. The average atomic mass of Helium, however, is 4.003.

Protons have a positive charge, the neutrons are neutral, and electrons have a negative charge. If you think about magnets, a north pole will repel another north pole, but it attracts a south pole. It is similar with atoms. The protons are repelled, and the neutrons allow the protons to remain close together. The electrons have a negative charge, and they are attracted to the protons.

proton = neutron = electron =

Helium Element Helium Ion

Helium Isotope

Isotopes are atoms of an elements that differ in mass. The number of protons defines the element, so the difference in the mass is the number of neutrons in the nucleus. For example, our helium to the left now has an atomic mass of 5. The heavier atoms are much more rare than the lighter atoms, and we can find the percentage of the heavier elements by a simple ratio. Oxygen, with 8 protons, has three stable isotopes: 8 neutrons, 9 neutrons, or 10 neutrons.