Alaska Sea Grant

Teacher Background

Investigation 1: Where Did the Rubber Bath Toys Go?
A great book to use for this entire unit is Tracking Trash: Flotsam, Jetsam, and the Science of Ocean Motion by Loree Burns. Chapters 1 and 3 are a perfect fit with Investigation One. Chapter 3 is about the rubber bath toy spill and Chapter 1 is about the Nike shoe spill.

Story about the Rubber Duckies

Investigation 2: Weather and Circulation Systems
Chapter 2 of Tracking Trash works well with this investigation. Its title is “The Science of Ocean Motion.”

If you are unfamiliar with using the Socratic Seminar method for group discussion, take a look at these sites:
How to prepare for a Socratic seminar
Socratic Seminar Strategy Guide
Socratic seminar guidelines for students

Ocean Current Information
A good basic approach to determining currents is to estimate the contribution of each of the forcing mechanisms. For nearshore currents tides generally dominate, whereas on the open shelf winds dominate, tides are involved, and density plays a small role. For long-term drift applications, winds and density are more significant than tides.

Weather and wind influence currents only where weather is occurring (this may seem intuitive), whether it is a large weather system encompassing a thousand miles of ocean or just a local sea breeze in a small inlet. The influence of wind on currents gets more complex when wind-generated waves and swells travel far from their source area and affect other regions of the ocean. In this way it can be seen how the effect of wind and weather on ocean currents ranges from small-scale geographic regions to larger ones, just as it ranges from short time scales (hours) to large time scales (seasons) in duration.

While tide effects are not significant in influencing currents in large open swaths of water like ocean basins, tides are very influential on currents close to land, especially in areas where the topography exaggerates tidal effects. Turnagain Arm south of Anchorage, Kachemak Bay near Homer, Whittier’s Passage Canal, Seward’s Resurrection Bay, and Cook Inlet all experience significant tidal impacts. Tidal cycles are roughly 12 hours long with about 6 hours between a high and low tide.

The direction of tides doesn't always dictate the direction of the current. A good investigation for this section is to have students pit tidal influence against an opposing wind; the students' arguments on which one has more influence will help clarify their understanding of the conceptual underpinnings of currents.

The influence of water density on currents, driven by both thermal and salinity gradients, is less in shallow water near land masses, and more significant at increased depths. In fact, density gradients are the main driver in the exchange of surface and deep water.

Currents Tutorial from NOAA
Surface Ocean Currents
Ocean Odyssey – Density Current video from NASASciFiles
Covers density, salinity, currents
Ocean Odyssey – Surface Currents video from NASASciFiles
Global current image
Global isobaric patterns for July and Sept.
Ocean Circulation article
Global ocean current circulation animation:
Global wind speed Jan and July plus an animation
NOAA National Data Buoy Center 
Ocean Currents and The Distribution of Life
Ocean in Motion: Ekman Transport background
Wind Driven Surface Currents, Gyres Background:
Coriolis effect. Examine the Coriolis effect, which is responsible for the “spin” of a weather system. A lesson plan for a hands-on activity.

Investigation 3: Waves and Tides
Engagement. If you and your students don’t have much experience with tides, it is not hard to find stories about tides in Alaska on the Internet. 
Story about a cruise ship stuck at low tide  
Description of the hazards on the Turnagain mudflats
Story of a fisherman in Anchorage getting trapped at low tide
NOAA Ocean Service Education
Tides and Water Levels lesson plans

If students need more learning activities centered around tides to better understand the concepts, NOAA has lesson plans: Tides: Ups and Downs
Tides and Moon with time-lapse and marigrams
Kachemak Bay tidal cycle: the movie (time-lapse of Kachemak Bay extreme tidal cycle)
Ocean Odyssey – Tides and Waves video from NASASciFiles
Ocean Tides at the Bay of Fundy video
From: Britannica Online
Waves Includes information and interactive wave section

Investigation 4: Temperature and Salinity Effects on Deep Ocean Currents
Density background: Density is defined as mass per unit volume, or grams per cubic centimeter in the metric system. In fluid systems, one fluid floats on top of another if it has a density that is less than the other. The downward gravitational force of the upper layer is less than the upward buoyant force of the underlying fluid. Density differences can be caused by temperature, compositional, or pressure differences. In this experiment, the differences are based primarily on composition of the fluid. Even though all layers are fluids, they do not mix rapidly if handled gently, and will stay separate for a class period or more. Masses of subtly distinctive (having different temperatures or salinities) ocean water can persist for months and over distances of hundreds of kilometers. Given these properties, scientists can identify and track water masses, and learn about the speed and path of various water masses around the world.

Online sources for Tornado Tubes
Edmund Scientifics

Investigation 5: Seafloor Topography
Sea Bottom Features draining the Atlantic and Pacific Oceans.

Investigation 6: Debris Detectives Field Trip
Chapter 5 of Tracking Trash is about monster debris.

Investigation 7: Global Conveyor Belt
Chapter 4 of Tracking Trash is about the North Pacific Gyre and the Pacific garbage patch.
Global conveyor belt audio radio show
Oceanic Conveyor Belt background
Turning the Tides video

Hypothetical Landmass resources:
Pangaea Supercontinent
Pangaea: Wikipedia

Exxon Valdez Oil Spill resources
Prince William Sound is a small inland sea in that it is wide enough to have appreciable horizontal cyclonic circulation. It is also a fjord in that it has basin depths to 700 m but is silled at 180 m to the open ocean. The general circulation pattern is defined by a portion of the westward flowing Alaska Coastal Current on the Gulf of Alaska shelf that enters Prince William Sound through Hinchinbrook Entrance and transits the sound from east to west before exiting through Montague Strait and rejoining the coastal current. However, there is much variability in this circulation, especially in the transport through Hinchinbrook Entrance.

Niebauer, H.J., T.C. Royer, and T.J. Weingartner. 1994. Journal of Geophysical Research 99(14):113-114, 126.
Map showing Bligh Reef and the spill location
NOAA Fisheries Office of Exxon Valdez Oil Spill (EVOS) Damage Assessment and Restoration
Map of where the oil went
The behavior of the oil
Radio show about currents in Prince William Sound

Hypothetical Spill resources
Oil and Chemical Spills
Beach: Nike Shoes Wash Up
LEGOs and Other Floating Flotsam
Flip Flotsam video
Drifter Buoys

Garbage Patch in the Pacific resources
Trashed: Across the Pacific Ocean, Plastics, Plastics, Everywhere
Why is the world’s biggest landfill in the Pacific Ocean?
Surface Ocean Currents
Wind Driven Surface Currents: Gyres Background
Plastics and Marine Debris video
6 min.
Turning the Tides video
The Garbage Patch video
Gorilla in the Greenhouse: The Great Pacific Garbage Patch

Alaska Sea Grant University of Alaska Fairbanks Alaska Department of Education and Early Development NOAA