Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "fastened" to a fixed object, drift ice is carried along by winds and sea currents, hence its name. When drift ice is driven together into a large single mass (>70% coverage), it is called pack ice. Wind and currents can pile up that ice to form ridges up to tens of metres in thickness. These represent a challenge for icebreakers and offshore structures operating in cold oceans and seas. Drift ice consists of ice floes, individual pieces of sea ice or more across. Floes are classified according to size: ''small'' – to ; ''medium'' – to ; ''big'' – to ; ''vast'' – to ; and ''giant'' – more than . Drift ice affects: * Security of

navigation Navigation is a field of study that focuses on the process of monitoring and controlling the movement of a craft or vehicle from one place to another.Bowditch, 2003:799. The field of navigation includes four general categories: land navigation ...

* Climatic impact (see Polar ice packs) * Geological impact * Biosphere influence (see Ecology of sea ice) Drift ice can exert tremendous forces when rammed against structures, and can shear off rudders and propellers from ships and strong structures anchored to the shore, such as piers. These structures must be retractable or removable to avoid damage. Similarly, ships can get stuck between drift ice floes. The two major ice packs are the

Arctic ice pack The Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall ...

and the Antarctic ice pack. The most important areas of pack ice are the polar ice packs formed from

seawater Seawater, or salt water, is water from a sea or ocean. On average, seawater in the world's oceans has a salinity of about 3.5% (35 g/L, 35 ppt, 600 mM). This means that every kilogram (roughly one liter by volume) of seawater has appro ...

in the Earth's

polar region The polar regions, also called the frigid zones or polar zones, of Earth are the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitudes are dominated by flo ...

s: the Arctic ice pack of the

Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately and is known as the coldest of all the oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, a ...

and the Antarctic ice pack of the

Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. With a size of , it is regarded as the second-smal ...

. Polar packs significantly change their size during seasonal changes of the year. Because of vast amounts of water added to or removed from the oceans and

atmosphere An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...

, the behavior of polar ice packs has a significant impact on global changes in

climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologi ...

. Image:Kontio towing.jpg, The icebreaker ''Kontio'', which in this picture became stuck in drift ice while towing a cargo ship in pack ice in the northern

Baltic sea The Baltic Sea is an arm of the Atlantic Ocean that is enclosed by Denmark, Estonia, Finland, Germany, Latvia, Lithuania, Poland, Russia, Sweden and the North and Central European Plain. The sea stretches from 53°N to 66°N latitude and from ...

Image:IceNomenclature-2LightPack.jpg, Ice floes / pack ice Image:Wrangelisland.jpg, Satellite image of drift ice in the

around Wrangel Island Image:Icebreaker Aurora on drift ice at Sea of Okhost.jpg, Drift ice in the

Sea of Okhotsk The Sea of Okhotsk ( rus, Охо́тское мо́ре, Ohótskoye móre ; ja, オホーツク海, Ohōtsuku-kai) is a marginal sea of the western Pacific Ocean. It is located between Russia's Kamchatka Peninsula on the east, the Kuril Islands ...

Image:Aboard Aurora Icebreaker at Sea of Okhost.jpg, Aboard the ''Aurora'' icebreaker in the Sea of Okhotsk Seasonal ice drift in the

by the northern coast of

Hokkaidō is Japan, Japan's Japanese archipelago, second largest island and comprises the largest and northernmost Prefectures of Japan, prefecture, making up its own List of regions of Japan, region. The Tsugaru Strait separates Hokkaidō from Honshu; th ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

, has become a tourist attraction, and is one of the

100 Soundscapes of Japan In 1996, as part of its efforts to combat noise pollution and to protect and promote protection of the environment, the Ministry of the Environment designated the . There were 738 submissions received from all over the country and the 100 "best" wer ...

. The Sea of Okhotsk is the southernmost area in the

Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's Nort ...

where drift ice may be observed.

References

External links

"Ice in the Sea"
: chapter from

Nathaniel Bowditch Nathaniel Bowditch (March 26, 1773 – March 16, 1838) was an early American mathematician remembered for his work on ocean navigation. He is often credited as the founder of modern maritime navigation; his book '' The New American Practical Navi ...

's ''American Practical Navigator''
Cryosphere Today : Current Arctic sea ice conditions

Data source for sea ice picture

Marine Modeling and Analysis Branch

* ttp://www.arctic.noaa.gov/detect/animations/halfsize_20030928-20040510.avi Animation of the movement of sea ice, September 2003 through May 2004
Atlas of Antarctic Sea Ice Drift

The Papers of Paul Gordienko on Ice and Ice Drifts
at Dartmouth College Library {{DEFAULTSORT:Drift Ice Sea ice Oceanography

See also

References

External links