ice, the ocean and pack ice

8/6/2019 Ice, The Ocean and Pack Ice

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Presented By: Colin Bursey and Carla Penney


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` Sea ice forms where seawater cools below its initial

freezing point (which is typically around -2C)

`

The cooling water continues to sink awayfrom thesurface until ice begins to form

` As ice forms, a majority of the dissolved salts are

excluded from the ice and remain in the unfrozen

water (thus, the salinity increases in the unfrozenwater which decreases its freezing point)


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` Grease Ice Grease ice is formed when frazil ice (tiny, needle-like ice particles) on

the surface of the water is stirred by wind and waves

` Pancake Ice

Pancake ice isformed when newly

formed ice is broken apart by wavesand wind and smashed against each other

` Ice Floes Pancake ice fuse together to form ice sheets when are then broken

apart by waves and wind to form ice floes. Ice floes constantly move andshift, freeze together and break loose, buckle up orflatten out as ice

moves

` Pack Ice Pack is generally formed when ice floes expand and begin to raft onto

one another to cover the seas surface


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` The North and South Poles (polar ocean zones) arecovered with ice and their ocean surface temperatureremain at or close to freezing year round because of theheat-buffering effect of ice (ice is not a good conductor!)

` The polar ocean zones, subpolar zones and particularly theArctic Ocean have relatively low salinity Salinity is lowered by ice exclusion during the continual freeze-

and-thaw cycle that creates sea ice

` When sea ice melts in the spring and summer, the non-

salty water that is released from the ice mixes with theupper layer of the ocean, lowering its salinity


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` Characteristics Forms at sea and moves with currents and winds

This movement of ice causes them to fuse together

forming mounds called hummocks orpressure ridges

Can be up to ~2m thick during winter in polar latitudes


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` Distribution Pack ice forms around the margin of the Arctic Sea

It extends through the Bering Strait and into the sea on

the Pacific side and as far south as Newfoundland and

Nova Scotia (in the North Atlantic)

Reaches its maximum extent during May and breaks to

cover its least area in September

The polar ice cap is composed ofmulti-year pack ice


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` Transportation Pack ice is generally transported by wind but also can be

carried by surface currents


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` The main effect ofpack ice on the Earth is thedeposit ofboulders on coastlines to formbarricades

` These barricades are formed when boulder-ladenice rafts are grounded during ice break-up in thespring

` Often times these boulder barricades can beseen in a linearfashion or randomly deposited


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` Pack ice found in the polar regions can have an

effect on the Earths climate

` Additionally, it can have an effect on the Earths

atmosphere by influencing the atmospheric

concentration ofcarbon dioxide (pCO2)


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` Gross M. G. & Gross E (1996) Oceanography: A View of the Earth(7th ed.),Prentice Hall: USA

` Pinet, P.R. (2009) Invitation to Oceanography(5th ed.) Jones and Bartlett:Sudbury, MA.

`

Segar,D

. A. (2007) Introduction to

Ocean Science (2

nd

ed.)W

.W

. Norton &Company: New York, NY.

` Sun, X., and K. Matsumoto (2010), Effects ofsea ice on atmosphericpCO2: Arevised view and implications for glacial and future climates, J. Geophys. Res.,115, G02015, doi:10.1029/2009JG001023.

` Rosen, P. S. (1979), Boulder Barricades in Central Labrador, Journal of

SedimentaryPetrology., 49(4), 1113-1124

` Thruman, H.V. (1997) IntroductoryOceanography(8th) Prentice Hall: UpperSaddle River, NJ.

ice, the ocean and pack ice

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