De-mystifying the "Great Pacific Garbage Patch"
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Frequently Asked Questions
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Are the “garbage patches” the only areas where marine debris concentrates?
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What is the difference between the "gyre" and the “garbage patches”? Or are they the same thing?
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Is debris cleanup feasible in the “garbage patches” and other areas of our oceans?
NOTE: This map is an oversimplification of ocean currents and features in the Pacific Ocean. There are numerous factors that affect the location, size, and strength of all of these features throughout the year, including seasonality and El Nino/La Nina. Depicting that on a static map is very difficult.
What are the “garbage patches”?
The “garbage patch,” as referred to in the media, is an area of marine debris concentration in the North Pacific Ocean. The name “garbage patch” has led many to believe that this area is a large and continuous patch of easily visible marine debris items such as bottles and other litter—akin to a literal blanket of trash that should be visible with satellite or aerial photographs. This is simply not true. While litter items can be found in this area, along with other debris such as derelict fishing nets, much of the debris mentioned in the media these days refers to small bits of floatable plastic debris. These plastic pieces are quite small and not immediately evident to the naked eye. For more information on this type of debris visit our page on plastics.
What’s in a name? - The name “garbage patch” is a misnomer. There is no island of trash forming in the middle of the ocean nor a blanket of trash that can be seen with satellite or aerial photographs. This is likely because much of the debris found here is small bits of floating plastic not easily seen from a boat.
Where are the “garbage patches”?
Eastern Pacific garbage patch - Concentrations of marine debris have been noted in an area midway between Hawai‘i and California within the North Pacific Subtropical High, an area between Hawaii and California. Due to limited marine debris samples collected in the Pacific it is still difficult to predict its exact content, size, and location. However, marine debris has been quantified in higher concentrations in the calm center of this high-pressure zone compared to areas outside this zone. It should be noted that the North Pacific Subtropical High is not a stationary area, but one that moves and changes. This area is defined by the NOAA National Weather Service as "a semi-permanent, subtropical area of high pressure in the North Pacific Ocean. It is strongest in the Northern Hemispheric summer and is displaced towards the equator during the winter when the Aleutian Low becomes more dominant. Comparable systems are the Azores High and the Bermuda High." The High is not a stationary area, but one that rotates, moves, and changes.
Western Pacific garbage patch - There is a small "recirculation gyre" south of the Kuroshio current, off the coast of Japan that may concentrate floating marine debris; the so-called western garbage patch. The exact forces that cause this clockwise rotation are still being researched; however it may be caused by winds and ocean eddies (clockwise or counter-clockwise rotating waters). Research is ongoing by academia such as the University of Hawaii and Massachusetts Institute of Technology, to further understand the true nature of and forces behind these recirculation gyres.
Are the Pacific “garbage patches” the only areas where marine debris concentrates?
The “patches” are not the only open ocean areas where marine debris is concentrated. Another important area is the North Pacific is the Subtropical Convergence Zone (STCZ). This area, located north of the Hawaiian archipelago, has a high abundance of marine life, is a known area of marine debris concentration, and is one of the mechanisms for accumulation of debris in the Hawaiian Islands (Pichel et al., 2007).
Oceanographic features similar to the North Pacific Subtropical High and STCZ exist in other oceans of the world. Little research to date has been conducted on marine debris in these areas. Because of this no one can say for sure how large these areas are, especially since they move and change, sometimes daily, and no accurate estimate exists of how much debris is out there.
Regardless of the exact size, mass, and location of these areas of concentration, man-made litter and debris do not belong in our oceans or waterways.
See below and our page on Marine Debris Movement for more information.
North Pacific Subtropical Convergence Zone (STCZ)
The STCZ is located along the southern edge of an area known as the North Pacific Transition Zone (click here for detailed information on the Transition Zone). NOAA has focused on the STCZ because it is an area of high productivity, pelagic species feeding and migration, and documented marine debris concentration – and one of the reasons for marine debris accumulation in Hawaii (see below) (Kubota, 1994; Pichel et al., 2007). This area does not have distinct boundaries and varies in location and intensity of convergence throughout the year. This zone moves seasonally between 30° and 42° N latitude (approximately 800 miles), extending farther south (28°N) during periods of El Niño (Donohue and Foley, 2007). It is less well defined and located more northerly during the summer months, when convergence tends to be weaker, and is sharper and located farther south during winter months, when convergence is stronger.North Pacific Subtropical Convergence Zone as a mechanism for accumulation of marine debris in Hawaii:
The Hawaiian Archipelago, extending from the southernmost island of Hawaii 1,500 miles northwest to Kure Atoll, is among the longest and most remote island chains in the world. In Hawaii, marine debris continues to present a hazard to marine habitat, safe navigation, and wildlife, including the endangered Hawaiian monk seal (Monachus schauinslandi) and various species of sea turtles, seabirds, and whales. It is the location of this archipelago, between 18° and 28° N latitude, which makes it prone to the accumulation of marine debris. One of the reasons marine debris accumulates in these islands is the movement of debris within the North Pacific Subtropical Convergence Zone (STCZ). The STCZ concentrates debris and moves seasonally between 30° and 42° N latitude, dipping farther south (28°N) during periods of El Niño. This accumulation due to the STCZ is evidenced by an increase in the quantity of floating marine debris deposited on beaches during El Niño periods (Morishige et al., 2007). Additionally, a correlation has been noted between increased entanglements of endangered Hawaiian monk seals in marine debris and periods of El Niño (Donohue and Foley, 2007).
What is the difference between the "gyre" and the “garbage patches”? Or are they the same thing?
A gyre is a large-scale circular feature made up of ocean currents that spiral around a central point, clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. Worldwide, there are five major subtropical oceanic gyres: the North and South Pacific Subtropical Gyres, the North and South Atlantic Subtropical Gyres, and the Indian Ocean Subtropical Gyre. The North Pacific Subtropical Gyre is the one most notable because of its tendency to collect debris. It is made up of four large, clockwise-rotating currents – North Pacific, California, North Equatorial, and Kuroshio. It is very difficult to measure the exact size of a gyre because it is a fluid system, but the North Pacific Subtropical Gyre is roughly estimated to be approximately 7 to 9 million square miles—not a small area! This, of course, is a ballpark estimate. This is equivalent to approximately three times the area of the continental United States (3 million square miles).
While a gyre may aggregate debris on a very large scale, debris patches, as seen by those sailing the North Pacific, are actually the result of various smaller-scale oceanographic features such as oceanic eddies and frontal meanders (think of meanders as the deviation from a straight line. As energy (wind/currents) hit the front there are undulations and "curvature" which are described as frontal meanders (movements to the north and south along the front)).
How big are the “garbage patches”?
The reported size and mass of these "patches" have differed from media article to article. Due to the limited sample size, as well as a tendency for observing ships to explore only areas thought to concentrate debris, there is really no accurate estimate on the size or mass of the “garbage patch” or any other concentrations of marine debris in the open ocean. Additionally, many oceanographic features do not have distinct boundaries or a permanent extent, and thus the amount of marine debris (both number and weight) in this zone would be very difficult to measure accurately. The “patchiness” of debris in this expansive area would make a statistically sound survey quite labor-intensive and likely expensive.
Again, regardless of the exact size, mass, and location of the “garbage patch,” manmade debris does not belong in our oceans and waterways.
What is the main debris type found in these patches?
Plastics. Likely because of the abundance of plastics and the fact that some common types of plastic float.
Can you see the “garbage patches” with satellite photos?
NO. Relative to the expanse of the North Pacific Ocean, sightings of large concentrations of debris, especially of large debris items are not very common. A majority of the debris observed in the “garbage patch” is small plastic pieces. Small debris pieces are difficult to see due to their size, and many of these pieces may be suspended below the surface of the water, which would make them even harder to see, even with the human eye. For these reasons, the debris, or “patch” of debris is not visible with existing satellite technology.
Is debris cleanup feasible in the “garbage patches” and other areas of our oceans?
The answer to this is not as simple as you may think. It is certainly not cost-effective to skim the surface of the entire ocean. Even a cleanup focusing on “garbage patches” would be a tremendous challenge. Keep in mind these points:
- Concentration areas move and change throughout the year
- These areas are typically very large (see below)
- The marine debris is not distributed evenly within these areas
- Modes of transport and cleanup will likely require fuel of some sort
- Most of the marine debris found in these areas is small bits of plastic
This all adds up to a bigger challenge than even sifting beach sand to remove bits of marine debris. In some areas where marine debris concentrates, so does marine life (as in the STCZ). This makes simple skimming the debris risky—more harm than good may be caused. Remember that much of our ocean life is in the microscopic size range. For example, straining ocean waters for plastics (e.g., microplastics) would capture the plankton that are the base of the marine food web and responsible for 50% of the photosynthesis on Earth… roughly equivalent to all land plants!
Also, keep in mind that our oceans are immense areas! The Pacific Ocean is the largest ocean on the planet covering nearly 30% of Earth’s surface area (~96 million square miles, or ~15 times the size of the continental US). Surveying less than 1% of the North Pacific Ocean, a 3-degree swath between 30° and 35°N and 150° to 180°W, requires covering approximately 1 x 106 km2. If you traveled at 11 knots (20 km/hour), and surveyed during daylight hours (approximately 10 hours a day) the area within 100m off of each side of your ship (Mio et al., 1990), it would take 68 ships one year to cover that area! Now, add to that the fact that these areas of debris concentration have no distinct boundaries, move throughout the year, and are affected by seasons, climate, El Nino, etc.
Is there a “garbage patch” in the Atlantic Ocean?
Much like in the Pacific, there is a North Atlantic Subtropical Gyre made up of four major currents – North Equatorial, Gulf Stream, North Atlantic, and Canary Current. There is also a North Atlantic Subtropical Convergence Zone (STCZ). It’s Pacific sister is a known area of marine debris concentration and is in fact one of the mechanisms of debris deposition in the Hawaiian Islands. Similarly, there are areas of oceanic convergence and eddies (areas that in the Pacific concentrate debris – e.g., western garbage patch) in the Atlantic.
There has been research conducted and published on marine debris in the Atlantic, mainly on ingestion in Atlantic species of sea turtles and seabirds or on nearshore trawls for plastic particles. There have also been anecdotal reports and some studies of debris concentrations, most notably, Sea Education Association's work in the western North Atlantic and Caribbean Sea (Law et al., 2010). Still, compared to the North Pacific Ocean, there is a paucity of published literature on marine debris in the high-seas Atlantic Ocean.
Literature Cited
Donohue, M. and D. Foley. 2007. Remote sensing reveals links among the endangered Hawaiian monk seal, marine debris, and El Niño. Marine Mammal Science 23(2):468-473.
Kubota, M. 1994. A mechanism for the accumulation of floating marine debris north of Hawaii. Journal of Physical Oceanography 24:1059–1064.
Law, K., S. Moret-Ferguson, N. Maximenko, G. Proskurowski, E. Peacock, J. Hafner, and C. Reddy. 2010. Plastic Accumulation in the North Atlantic Subtopical Gyre. Science Express. 19 August 2010 issue.
Mio, S.I., S. Takehama, and S. Matsumura. 1990. Distribution and density of floating objects in the North Pacific based on 1987 sighting survey. In: R.S. Shomura and M.L. Godfrey, Editors, Proceedings of the Second International Conference on Marine Debris2–7 April, 1989, US Dept. Commer., NOAA Tech. Memo. NMFS, NOAA-TM-NMFS-SWFSC-154, pp. 212–246 Honolulu, Hawaii.
Morishige, C., M. Donohue, E. Flint, C. Swenson, and C. Woolaway. 2007. Factors affecting marine debris deposition at French Frigate Shoals, Northwestern Hawaiian Islands Marine National Monument, 1990-2002. Marine Pollution Bulletin 54: 1162-1169.
Pichel, W., J. Churnside, T. Veenstra, D. Foley, K. Friedman, R. Brainard, J. Nicoll, Q. Zheng, and P. Clemente-Colon. 2007. Marine debris collects within the North Pacific Subtropical Convergence Zone. Marine Pollution Bulletin 54: 1207-1211.
Acknowledgement
This information was compiled with the input and assistance of NOAA researchers, Hawaii longline fishermen, recreational boaters, Seba Sheavly (Sheavly Consultants), and in particular oceanographers with the NOAA Pacific Islands Fisheries Science Center.
