Updated with 2014 results

links scipy-conference#1

2014/entry12/index.rst

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+Entry 12
+========
+
+.. image:: entry12.png
+
+Authors
+-------
+- Filipe Pires Alvarenga Fernandes
+
+Abstract
+--------
+
+The IPython notebook demonstrate how to calculate and plot the mixing
+percentage of the three major `water masses`_ from the South Atlantic.
+
+The data used is freely available, and consist of temperature and salinity
+downloaded from the `World Ocean Atlas 2009`_.
+
+The mixing percentage of each water mass is obtained by solving a linear system
+of equations where we have 3 unknowns and three equations according to `Mamayev
+(1975)`_:
+
+:math:`m_1T_1 + m_2T_2 + m_3T_3 = T`
+
+:math:`m_1S_1 + m_2S_2 + m_3S_3 = S`
+
+:math:`m_1 + m_2 + m_3 = 1`
+
+where,
+- :math:`T, S` are the temperature and salinity data where we want to know the mixing rations;
+- :math:`T_n, S_n` the temperature and salinity pairs for the water masses core 1, 2, and 3;
+- :math:`m_1, m_2, m_3` the water mass mixing percentages we are looking for.
+
+The water masses we will investigate are the: South Atlantic Central Water
+`SACW`_ formed in the center of the South Atlantic Subtropical Gyre; the
+Antarctic Intermediary Water `AAIW`_ formed in the Antarctic Convergence zone
+originated by upwelling the North Atlantic Deep Water `NADW`_; and last but not
+least the NADW, which is formed across the Greenland-Iceland-Scotland Ridge.
+We could include more water masses in the analysis, for example: the Antarctic
+Bottom Water `AABW`_ and/or the Circumpolar Deep Water `CDW`_.  However, that
+would require two more equations, and therefore two more conservative
+properties.  Temperature and Salinity are the easiest conservative variables to
+compute.  Other variables like oxygen, silicate and etc could be used, but
+would require a special treatment to became quasi-conservative to be included
+in the analysis.
+
+The contouring of the mixing percentages is a simple, yet powerful tool to
+understand mixing the ocean.
+
+Caveat: The water masses cores used here were modified and may not correspond
+directly with the cores found in the `literature`_.  The reason for that was to
+show both the Tropical Water and the South Atlantic Central Water as one water
+mass.
+
+The figure: Matplotlib allows us to contour the results with three separated
+colormaps, facilitating the interpretation.  A world map inset shows the
+transect (in red) of the data.  In additional, we plot the Temperature-Salinity
+Diagram (T-S), to help visualize each the water mass center.  The T-S diagram
+displays the seawater density (as gray contours) from lighter to heavier water
+(at the top and at the bottom of the figure respectively) and the meridional
+mean of the temperature and salinity.
+
+interpretation: We can see that we have both AAIW and SACW cores (100%) in our
+domain.  We can also note that, even though the SACW occupies the majority of
+the T-S diagram range, it is not the major water mass in our domain.  Another
+important remark is that the NADW reaches from the North Atlantic all the way
+to the Antarctica, where it mixes with colder and fresher water to creates the
+AAIW.  That is an important part to the global Conveyor Belt (or Thermohaline
+Circulation).
+
+The "white" gap at bottom the contour represents the AABW and the CDW that are
+not resolved in our model.  The overlap of the contour is an evidence of a poor
+choice for the water mass cores (probably bad choices for the water masses
+cores).
+
+.. _water masses: http://glossary.ametsoc.org/wiki/Water_mass
+
+.. _World Ocean Atlas 2009: http://www.nodc.noaa.gov/OC5/WOA09/pr_woa09.html
+
+.. _Mamayev (1975): http://www.elsevier.com/books/temperature-salinity-analysis-of-world-ocean-waters/mamayev/978-0-444-41251-5
+
+.. _SACW: http://glossary.ametsoc.org/wiki/Central_water
+
+.. _AAIW: http://en.wikipedia.org/wiki/Antarctic_Intermediate_Water
+
+.. _NADW: http://en.wikipedia.org/wiki/North_Atlantic_Deep_Water
+
+.. _AABW: http://en.wikipedia.org/wiki/Antarctic_Bottom_Water
+
+.. _CDW: http://en.wikipedia.org/wiki/Circumpolar_deep_water
+
+.. _literature: http://archimer.ifremer.fr/doc/00110/22090/19731.pdf
+
+Products
+--------
+
+- :download:`PDF <mixing_ratio.pdf>`
+
+Source
+------
+
+- :download:`IPython notebook <water_mass.html>` (:download:`ipynb <water_mass.ipynb>`)