.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "api/gallery/glaciology/plot_11_dansgaard_isotope_thermometer.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_api_gallery_glaciology_plot_11_dansgaard_isotope_thermometer.py>`
        to download the full example code or to run this example in your browser via JupyterLite.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_api_gallery_glaciology_plot_11_dansgaard_isotope_thermometer.py:


Dansgaard's isotope thermometer (1964)
======================================

Willi Dansgaard collected rain and snow from stations worldwide and found
that their oxygen-18 content falls by about 0.7 permil per kelvin of mean
annual temperature at high latitudes: as moist air cools, its heavy
molecules condense first. Read backwards, the isotope ratio of ice is a
thermometer, and the glacial ice of Greenland, about 7 permil lighter than
Holocene ice, records a cooling of about 10 K.

.. GENERATED FROM PYTHON SOURCE LINES 12-35



.. image-sg:: /api/gallery/glaciology/images/sphx_glr_plot_11_dansgaard_isotope_thermometer_001.png
   :alt: Dansgaard: glacial ice 10 K colder
   :srcset: /api/gallery/glaciology/images/sphx_glr_plot_11_dansgaard_isotope_thermometer_001.png
   :class: sphx-glr-single-img





.. code-block:: Python


    import matplotlib.pyplot as plt
    import numpy as np

    from earthsciencekit.glaciology import dansgaard_delta, dansgaard_temperature

    slope, offset = 0.69, -13.6
    station = np.array([258.0, 248.0, 263.0, 241.0, 268.0, 253.0, 233.0, 271.0])  # K, synthetic stations
    scatter = np.array([0.6, -0.8, 0.3, 1.1, -0.4, -0.2, 0.7, -0.9])  # permil
    measured = dansgaard_delta(station, slope, offset) + scatter
    assert np.isclose(np.polyfit(station, measured, 1)[0], slope, atol=0.05)
    holocene, glacial = dansgaard_temperature(np.array([-35.0, -42.0]), slope, offset)
    assert np.isclose(holocene - glacial, 7 / slope)

    fig, ax = plt.subplots()
    line = np.linspace(225, 280, 2)
    ax.plot(station - 273.15, measured, "o", label="synthetic stations")
    ax.plot(line - 273.15, dansgaard_delta(line, slope, offset), label="0.69 permil/K")
    title = f"Dansgaard: glacial ice {holocene - glacial:.0f} K colder"
    ax.set(xlabel="mean annual temperature [degC]", ylabel="delta-18O [permil]", title=title)
    ax.legend()

    plt.show()


.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (0 minutes 0.085 seconds)


.. _sphx_glr_download_api_gallery_glaciology_plot_11_dansgaard_isotope_thermometer.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: lite-badge

      .. image:: images/jupyterlite_badge_logo.svg
        :target: ../../../lite/lab/index.html?path=api/gallery/glaciology/plot_11_dansgaard_isotope_thermometer.ipynb
        :alt: Launch JupyterLite
        :width: 150 px

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: plot_11_dansgaard_isotope_thermometer.ipynb <plot_11_dansgaard_isotope_thermometer.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: plot_11_dansgaard_isotope_thermometer.py <plot_11_dansgaard_isotope_thermometer.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: plot_11_dansgaard_isotope_thermometer.zip <plot_11_dansgaard_isotope_thermometer.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_