Lab 7 – Water Masses
Watch this video clip:
This PBS video (https://www.youtube.com/watch?v=VumtklaO0SA) highlights one prediction of the impact of climate change – the slowing down of ocean circulation due to disruption of circulation in the north Atlantic. The sinking of dense water masses is one of the driving factors of global ocean circulation as are wind-driven surface currents, like the Gulf Stream. Both are part of what is called the Atlantic Meridional Overturning Circulation (AMOC). In this lab you will learn about water masses and their movements to explore what happens when density runs AMOC.
In the previous lab (Lab 6 Investigating Density and Layering in the Ocean), you learned how temperature and salinity control the density of seawater and how changes in density with depth lead to stratification (layering) in the ocean. Let’s do a quick check of what you learned in the video above and in Lab 6.
In this lab, you will continue to investigate the importance of seawater density and discover how it leads to circulation in the deep layers of the ocean, known as thermohaline circulation. You will also discover how differences in density can lead to unique bodies of water with distinct temperatures and salinities, referred to as water masses. You will learn how variations in water masses at locations along the east coast of the United States occur and can be detected, and the impact they have on marine organisms.
Learning Outcomes
- LO1. Demonstrate basic data literacy in graph interpretation by identifying changes in temperature, salinity and density through time, with water depth, and among water masses.
- LO2. Predict locations that are sources of deep-water thermohaline circulation and provide evidence to confirm this process.
- LO3. Describe how variation in water masses at a location can be identified and the impact these variations have on marine organisms.
- LO4. Interpret a TSD diagram to identify water masses in the ocean.
Background Information
Review concepts:
- Lab 3 – Building Data Skills – The display of oceanographic data
- Lab 3.1 – Reading a Time Series Graph
- Lab 6.1 – What is the Relationship Between Temperature, Salinity, and Density?
Key terms: salinity, density, thermohaline circulation, Gulf Stream, Mid Atlantic Bight
Data collection: We will use data collected by the Ocean Observatories Initiative, an initiative that has stationed equipment for collecting data in different locations around the world. Our data comes from the Coastal Pioneer Array MAB (Mid-Atlantic Bight), Coastal Endurance Array, and the Irminger Sea (see map below).
Image Credit: National Science Foundation’s Ocean Observatories Initiative
Sensors:
- Coastal Pioneer NES Offshore Surface Mooring Near Surface Instrument, Central Offshore Profiler Mooring Wire-Following Profiler
- Coastal Pioneer MAB Northern Profiler Mooring Wire-Following Profiler, Southern Surface Mooring Near Surface Instrument frame (would like to get Northern Profiler Mooring Surface Buoy
- Irminger Sea Flanking Mooring B (30, 90, 350, 100m)
Activities in this Lab
- Lab 7.1 – Thermohaline circulation: How does seawater density drive deep circulation in the oceans?
- Lab 7.2 – Importance of water masses along the coast: How do Gulf Stream influences impact fish populations on the East Coast?
- Lab 7.3 – TSD Diagrams: How do we use data to identify different water masses?
