Geography 2010A/B Study Guide - Quiz Guide: Geomorphology, Figured Bass, Permafrost

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29 Aug 2018

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Lake ice break up: lake ice melt occurs from both the surface and base once the ice was isothermal at. Melting at the surface depends on the albedo of the ice, which varies depending on snow and debris cover. Once surface snow melts, exposure of relatively dark congelation ice and high albedo snow ice will melt differentially. Melting occurs along the congelation ice crystal boundaries, resulting in candled ice. Continued melt thins the ice and the candling becomes increasing distinctive. During the melt process, ice on the shore is subject to enhanced melt. Shore ice is also thinner, and usually disintegrates early. Results in the formation of a moat around the perimeter of the lake. The open water of the moat is of tremendous biological significance and supports a variety of aquatic organisms. Ongoing ice decay is a combination of both melt and fragmentation of candled masses that rapidly melt.

Related Questions

An important question to consider when thinking about globalwarming is, "If the ice sheets near the poles melt, how much willthe sea level rise?" This seems like a difficult question, giventhe odd shapes of both the ice sheets and the oceans. But there aresome accurate approximations that allow the answer to be estimatedfairly accurately with reasonably simple calculations.

The critical idea is that both the thickness of the ice sheets andthe amounts of the sea-level rise are extremely small compared tothe radius of the earth. The radius of the earth is about 2/p x 107m -- more than 6000 kilometers. The ice sheet thicknesses we willbe concerned with are single digit miles and the sea level riseswill be in dozens of feet. As a result, in thinking about them, wecan essentially ignore the curvature of the earth. We can imaginepeeling the map of the earth off a globe and flattening it out (bymaking cuts, not by stretching it, so that we preserve the area).Then, both the ice and the sea level rise can be treated as right(not tilted) cylinders (though with funny shaped bases and tops).Since we know that the volume of a right cylinder is the area ofthe base times the height, we can easily estimate all the volumeswe need. A schematic picture of this approximation (with the heightof the ice mass greatly exaggerated -- you couldn't see it if Ididn't) is shown below. The error in these approximations is on theorder of the height of the cylinder considered divided by theradius of the earth; a very small number.
a. Assume that (after flattening the surface of the earth in ourimaginations) the ice sheet to be considered covers an area, A, andhas a thickness, d. The oceans currently cover about 75% of theearth's surface, and note that the surface area of a sphere is 4pr2where r is the radius of the sphere.

Generate an equation that will allow you to calculate h, the heightthe ocean levels will rise due to the melting of a an ice sheet interms of A, d, and r

b. As shown in the combined satellite photo on the right (fromGoogle Earth), Greenland is covered by a sheet of ice. This ice hasbeen measured to have a mean thickness of about 2 km. Recentobservations indicate that this ice sheet is beginning to retreat-- that it is melting at an accelerating rate.

Using the depth of the ice sheet and the scale given on thepicture, estimate how much sea level rise would be produced by themelting of the entire ice sheet lying on Greenland. (Note: You caneasily look this information up on the web. But the goal of thisproblem is in part to develop your estimation skills for thepurpose of building your ability to decide for yourself whether anygiven piece of information you find on the web is reasonable orbogus.)

Setup: I have an experiment testing a heat enging; with a gasfilled cylinder containing a piston with a scale on top of it, andthe cylinder is also connected to an aluminum can. The experimentis performed in four parts: 1) adding a weight onto the scale onthe cylinder (aluminum can in ice-water) - adiabatic process:pressure goes up but volume stays the same, 2) removing thealuminum can into bioling water - isobaric process: volumeincreases but pressure is same, 3) removing the weight from thescale - again adiabatic process: volume decreases, 4) taking thecan out of the boiling water and slowly submerging it into icewateragain - isobaric process.

What is a possible systematic error if the piston at the beginningof the experiment is placed high up in the gas cylinder (but stillhas room to move freely) instead of close to the bottom as in ourexperiment?

Geography 2010A/B Study Guide - Quiz Guide: Geomorphology, Figured Bass, Permafrost

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