What part of a lake thaws first?

Melting of lake ice usually occurs first near the shorelines or near the mouths of streams. At these points of contact with inflowing warm water, the ice melts faster than it does at central lake locations, where most melting is caused by the transfer of heat from the atmosphere.



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Lake ice freezes first at the surface starting at the edges or shoreline for two reasons. Water near the shore is typically shallower and contains less heat than deeper water so it can reach the freezing point faster than deeper water.

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Since water is good at holding heat, the more water there is, the more heat it will hold. This is why large deep lakes take longer freeze and melt than small shallow lakes. Water freezes from the perimeter of the lake to the center.

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The reason water freezes from the top down is because, unlike almost everything else, water gets less dense when it freezes. This is why ice cubes float in a drink.

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At some point, the ice layer itself on a lake will act as an insulator, preventing the cold air above the ice to remove heat from the unfrozen water below. This is why lakes don't typically freeze completely from top to bottom.

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Most lakes and ponds don't completely freeze because the ice (and eventually snow) on the surface acts to insulate the water below. Our winters aren't long or cold enough to completely freeze most local water bodies. This process of lakes turning over is crtically important to the life in the lake.

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Thick ice weakens slowly, but it also recovers slowly. While two inches of ice might last only two hours in moderate thaw conditions, a foot or more of ice can last several days.

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If you can see the ground through the ice, then there's going to be warmer water under it. Out in the middle, the ice grows thicker over the cold dark depths. Also, ice always melts away from the shore first.

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Ice is seldom the same thickness over a single body of water; it can be two feet thick in one place and one inch thick a few yards away.

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As a general rule of thumb, ice is safe to walk on when there is 4 inches or more of clear ice. It is important to understand that different types of ice varying in their strength. Clear blue or black ice is the strongest. This ice is formed from the lake water freezing.

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Just below the ice there is always a layer of colder water. The closer to freezing temperature, the closer to the ice. Once you get deep enough to where it gets to 4 C, then it will be that temperature all the way to the bottom.

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Do fish die in frozen lakes or in lakes that are partially frozen? Since fish are cold-blooded animals, they can survive because they are able to regulate their body temperature to match their environment. However, they could die if a body of water freezes over completely and remains frozen for an extended period.

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On the surface of lakes, or other bodies of still freshwater, congelation ice is often called black Ice. This ice has frozen without many air bubbles trapped inside, making it transparent. Its transparency reveals the colour, usually black, of the water beneath it, hence the name.

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That doesn't mean, however, when the air temp reaches 32 the lakes freeze. Water is a great insulator and good at holding heat, which is why the lake temperature doesn't fluctuate much day to day like the air does. Therefore, below freezing temperatures are needed for a week or more to form ice on a large lake.

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In water that is around the freezing point, a person is likely to survive only 15 to 45 minutes with flotation and possibly up to an hour or so with flotation and protective gear before the brain and heart stop (Table 1). The surface temperature of Lake Superior in early to mid-summer is about 40 to 50 F.

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Warm wind is the primary driver behind top surface melting. For example, over a 24-hour period at 50°F, strong (20-30 mile per hour) winds can cause over two inches of ice loss. In the same period, heavy rain and only moderate wind result in just one inch of ice loss.

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Ice will increase at a rate of 1 inch/15 freezing degree days. For example, if the average temperature over the last 24 hours was 25 degrees, subtract that from 32 degrees which will give you 7. Put 7 over 15 like a fraction, 7/15 equals about a 1/2 inch of ice over a 24-hour period.

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The high concentration of salt in ocean water lowers its freezing point from 32° F (0° C) to 28° F (-2° C). As a result, the ambient temperature must reach a lower point in order to freeze the ocean than to freeze freshwater lakes.

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