Salinity Matters (final)

Salinity Matters (final)
Created by: Carla Companion

In this activity, you will study the variation in concentration of dissolved salt (a.k.a. "salinity"). In addition, you will analyze water temperature and air temperature to discover how these have changed over the past 30 days. Video and interactive concept maps will provide a "bigger picture" view of ocean salinity and how it affects the water cycle, ocean circulation, and climate.

In this activity, you will study the variation in concentration of dissolved salt (a.k.a. "salinity"). In addition, you will analyze water temperature and air temperature to discover how these have changed over the past 30 days. Video and interactive concept maps will provide a "bigger picture" view of ocean salinity and how it affects the water cycle, ocean circulation, and climate.

Instructional Tips

Note that the data visualization instances (i.e., "near-river" and "near-ocean" examples) are set for the 30 days prior to when the student views them. So the data that they analyze will depend on when they view the two visualizations of their choosing (i.e., one "near-river" and one "near-ocean"). Note that the unit used for salinity graph is "psu" or "Practical Salinity Units," which is roughly equivalent to parts per thousand (ppt). PSU expresses salinity in the form of a mass fraction, i.e. the mass of the dissolved salts (grams) in a unit mass of seawater (kilogram). Given that students have a choice of stations to view, they could potentially choose two at vary different latitudes: i.e., Galveston, TX ("near-river") and Prince William Sound, AK ("near-ocean"). This exercise focuses on data ranges, trends and correlations for each station, followed by comparing / contrasting their results from the two stations. Thus, latitudinal differences between the stations should not be an important factor. However, if you would prefer that students examine two stations at similar latitudes, then you should instruct them to choose Dover, DE ("near-river") and Narragansett Bay, RI ("near-ocean"). In general, however, they will see that the ranges of salinity will be higher at the "near-river" stations because of river input and lower at "near-ocean" stations since these are located farther from freshwater river sources. They should notice that salinity values vary with tides since the estuary is being influenced by the ocean's motion (i.e., incoming tides move saltier water up the estuary and outgoing tides allow fresher water to travel further down the estuary). At any given station, the ranges for air temperature should be higher than those of water temperature because of the latter's higher heat capacity. Similarly, water temperature and air temperature may follow similar trends (e.g., higher at the beginning of the month and lower at the end of the month), although the water temperature may lag because of its higher heat capacity. There is a common misconception that salinity and water temperature are correlated (i.e., warmer water is saltier) but it is not the case. Higher salinities are associated with higher evaporation (which are not necessarily in warmer regions) or the freezing of seawater (which removes liquid water but leaves salt behind). There are many relationships between ocean salinity, the water cycle, ocean circulation and climate. These are summarized on the concept maps and their attached images/videos. However, the student should be able to distinguish when salinity values are a passive result of water cycle processes (i.e., evaporation, precipitation, etc.) versus an active "ingredient" in driving ocean circulation (i.e., determining seawater density along with temperature). Thus monitoring global ocean surface salinity helps us better understand climate patterns and change, specifically by (1) showing changes in the water cycle over the oceans; and (2) along with temperature, helping to determine how heat is distributed by ocean currents. The potential impact of dynamic environmental conditions on organisms in estuaries is complicated (for example, see http://estuaries.noaa.gov/About/Default.aspx?ID=231). However, the student should be able determine that estuaries have a variety of habitats (http://estuaries.noaa.gov/About/Default.aspx?ID=233; e.g., water column, oyster reefs, coral reefs, kelp and other macroalgae, rocky shores and bottoms, soft shores and bottom, submerged aquatic vegetation, coastal marshes, mangroves, deepwater swamps and riverine forests). In each of these estuarine habitats, native (or invasive) species have adapted to the natural variations in salinity. In terms of "global scale" impacts to organisms such as humans, changes in salinity and seawater density could affect ocean circulation patterns. Changes in the distribution of ocean heat could result in dramatic changes in weather and climate. For feedback or more information, please contact: Annette deCharon annette.decharon@maine.edu Carla Companion carlajean@gmail.com

Resources

NASA Aquarius website => http://aquarius.umaine.edu NOAA National Estuarine Research Reserve's "Estuaries Education" => http://estuaries.noaa.gov/Default.aspx

Data Investigation Details | Begin this Investigation