(Bloomberg) -- In the U.S., this past year has had more thanenough reminders of how weather can affect our lives.

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California is heading into its fourth year of drought because itdidn’t get enough snow. Boston is just emerging from a recordsnowpack. Almost every day, flights get canceled, children missschool and parents send checks off to insurance companies to guardagainst floods, hurricanes and tornadoes.

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Yet there are even longer-term impacts that most people mightnot notice. For instance, if you live in Canada, the northern U.S.or parts of Europe, the earth beneath your feet is rising. Thereason is, more or less, because of the weather.

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Not weather like yesterday’s rain, or last week’s wind. Thisphenomenon was caused by snows that piled up to create great icesheets that covered the land in the last Ice Age. OK, it was a lotof snow, over a long period of time, so it’s probably betterdescribed as climate than just weather.

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Regardless of the cause, the change can be seen.

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“We can monitor it in real time,” said Theresa Damiani, aresearch geologist at the National Oceanic & AtmosphericAdministration’s National Geodetic Survey in Camp Springs,Maryland.

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Earth Rebound

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The weight of the ice sheets, which were several miles thick inplaces, pushed down on the Earth’s surface. When the ice melted andretreated, the ground began to spring back.

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NOAA describes it as similar to what happens when an agingmattress returns to its original shape after a person gets up inthe morning. When the ice sheets first retreated, there was a quickrebound in many areas that slowed through the centuries, Damianisaid.

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“It has been rebounding and it still is,” Damiani said. “Ittakes a very long time.”

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The Earth’s surface rises about 1 millimeter a month in Canadaand about the same amount over the course of a year in the U.S.,she said. For a place like Canada’s Hudson Bay, the changes wouldbe apparent over a person’s lifetime, she said.

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“If you have a dock that you built, the ocean appears to begoing down,” Damiani said.

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It isn’t that the sea level is dropping -- it’s that the land isspringing back up.

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When researchers calculate the rise of the world’s oceansbecause of the current melting of glaciers and ice sheets, theyneed to keep the rebound rates in mind, according to a December2012 NOAA report.

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Area Covered

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Of course, the land is only rising in those areas covered by theice sheet. In the Western Hemisphere, that’s pretty much all ofCanada down through New England, across the Great Lakes and intothe Midwest, the northern Great Plains and Pacific Northwest.

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Beyond the limit of where the ice pushed the ground down, thereare areas where the surface is actually settling lower. Whathappened here is that the land at the edges of the ice sheets waslike jelly oozing out of a squashed sandwich.

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The changes can lead to small earthquakes, although those arevery weak and probably go unnoticed by most people.

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The motion is tracked using global positioning satellites and isused in making sure maps stay accurate, Damiani said.

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“My agency, the NGS, is tasked with monitoring the shape of theplanet,” Damiani said.

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The Scandinavian nations also track the rate of how the surfacehas been slowly rebounding over the past 14,000 years, give or takea century or two, since the ice sheets peaked in the last IceAge.

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Patience is definitely a job requirement.

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Copyright 2018 Bloomberg. All rightsreserved. This material may not be published, broadcast, rewritten,or redistributed.

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