Lab 7.1

Lab 7.1 – THE GULF STREAM CURRENT: HOW DO TROPICAL FISH SHOW UP IN NEW ENGLAND?

Fundamental concept: TBD
Estimated time to complete: 45 minutes
Data skills preparation: TBD
Materials needed: None

 

This cowfish was photographed offshore of Long Island, New York.  Cowfish are tropical species, found in warm waters near coral reefs.  So, what is this fish doing up near New York?  How did it get here?

It likely hitched a ride on the Gulf Stream!

In this lab, you will learn about the Gulf Stream, what type of data is used to detect its influence and the impact it has on fish populations.

 

Look at this animation of the currents at the surface of the ocean:

As the video zooms in on the east coast of the United States, you will notice an obvious current in the surface of the ocean shown by the concentration of moving white arrows. This is the Gulf Stream, and it is the most powerful surface current in the north Atlantic. You can think of the Gulf Stream as a river of warmer saltier water and, like rivers, the path of the current can meander (twist and turn).

Surface currents like the Gulf Stream are wind driven.  The water at the ocean surface moves as energy is transferred from the winds blowing along the surface of the ocean to the surface water. The surface currents are further modified due to the Coriolis Effect, the size and shape of ocean basins, and locations of the continents.

Let’s review some concepts before we dive into the Gulf Stream:

Quick Check Questions

As you have learned, the Gulf Stream is a powerful surface current that moves warm water northward along the western Atlantic  and tends to move offshore beginning near North Carolina. Sometimes there are intrusion events where the Gulf stream water moves over the continental shelf. Coastal waters over the continental shelf tend to remain cooler and less salty due to estuarine influences. Therefore, water in the Gulf Stream has a distinct temperature and salinity that allows oceanographers to distinguish it from other water masses such as water above the continental shelf.

Gawarkiewicz et al. (2018) did just that using data from the OOI Pioneer Array located over the New England shelf. The data suggested that onshore intrusions of warm, salty water (from the Gulf Stream) are becoming more prevalent. One consequence of this warm intrusion was the appearance of warm-water fish species that were presumably carried onto the continental shelf in January 2017 as part of one of these events.

The following graphs show data that points to this Gulf Stream intrusion event. The top graph shows salinity profiles over time. Each day is shown as a vertical bar that is color coded to show the salinity of the water from near the surface at 25m to the bottom at about 120m. The lower graph shows a time series of the salinity and temperature near the surface at 7m depth.  Notice the change in salinity during the event from January 8th through January 25, 2017.

[open in new window]

 

Application Question

1. Based on what you have learned, explain specifically how the cowfish that we featured at that start of this lab wound up off the coast of Long Island, New York. 

Reflection Question

1. If Gulf Stream intrusion events continue to become more frequent as the data suggests, speculate on the impact that you think this would have on the species that are native to the New England shelf ecosystem.

 

CITATION
Gawarkiewicz, G., R.E. Todd, W. Zhang, J. Partida, A. Gangopadhyay, M.-U.-H. Monim,
P. Fratantoni, A. Malek Mercer, and M. Dent. 2018. The changing nature of shelfbreak
exchange revealed by the OOI Pioneer Array. Oceanography 31(1):60–70.