8/6/2019 Ice Cover on the Great Lakes

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Ice Cover on the Great Lakes  NA

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Great Lakes Ice Cover Trends

Total ice cover on the Great Lakes has shown an

overall decline of ~15% over the period 1973-2009.

Over the middle to deepest parts of the Great Lakes,

the occurrence of very densely packed ice declined

by more than 30% over the period 1973-2002.

Near the lake shores, the occurrence of very densely

packed ice declined by ~20% over the period 1973-

2002.

Lake Superior has shown the greatest decrease in

total ice cover (~20% over the last 37 years).

Lake Ontario has shown the smallest decrease intotal ice cover (less than 10% over the last 37 years).

This past winter (2008/09) has shown that heavy ice

cover years do still occur and that natural interannual

variability in the internal climate system is a big

factor for ice cover on the Great Lakes, in addition to

anthropogenic causes.

EFFECT OF ICE ON THE REGION

The Fishing Industry: Ice cover in the shallow waters where whitesh spawn protects their eggs rom destructive windand wave action. Ice cover with little or no snow cover allowlight penetration at the surace to promote algae growth Algae are the base o the ood chain supporting all other liein the lakes, including valuable commercial and sportshspecies. With $4 billion owing into the commercial andsport shing industry each year, ice cover is a signicantconsideration.

The Costal Zone: In bays and other nearshore areas, iceorms a stable platorm or winter recreational activity suchas ice shing. Tis stable ice also protects wetlands and theshoreline rom erosion. Tough these are positive efects, theyalso have negative consequences. Huge ice jams can orm inrivers connecting the Great Lakes. Tese jams constrict theow o water rom one lake to another, causing oodingupstream and less water or hydropower plants downstream When the jam nally breaks, the resulting surge o ice and water can damage the shoreline and property.

Lake Water Levels and Navigation:  Heavy ice cover inthe winter can reduce the amount o evaporation rom theGreat Lakes, thus contributing to higher water levels. Tis isgood news or shippers because it means they can carry morecargo. However, heavy ice conditions in early spring candelay the shipping season and cause navigational problemsHigh lake levels are also a benet to marina operators, whospend millions to dredge boat slips, channels, and harbors when lake levels were low.

Ice on the Great Lakes is more than just a signal of winter.

In fact, the lakes were formed over several thousands of 

years as mile-thick layers of glacial ice advanced and

retreated, scouring and sculpting the basin. In addition,

the ebb and ow of glacial meltwater and rebound of theunderlying land from the weight of the massive ice sheets

further changed the basin’s shape and drainage patterns.

Ice cover still has a major effect on the Great Lakes,

making it more important than a connection to the past

and a measure of the winter’s harshness. Ice cover has an

effect on almost every aspect of life on the Great Lakes,

from hydropower generation to commercial shipping to the

shing industry. The amount of ice cover and how long it

remains on the lakes during the winter season changes from

year to year, and long-term changes may occur because of global warming. Studying, monitoring, and predicting ice is

important to determine climate patterns, lake water levels,

water movement patterns, water temperature structure, and

for predicting spring plankton blooms.

Grand Marais Observation Platform in Lake Superior on

February 13, 2008. Photo courtesy NWS Marquette, MI.

NOAA Great Lakes Environmental Research Laboratory ◆ 4840 S. State Rd. ◆ Ann Arbor, MI 48108 ◆ www.glerl.noaa.gov ◆ January 201

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GLERL Research

Forecast capability needed On Feb. 7, 2009, a warm and sunny winter day n Lake Erie, a large ice ow broke away romhe shoreline and stranded 134 sherman 1,000

yards ofshore. One man ell into the water andater died. Tough ice on western sections o 

he lake was nearly 2 eet thick, the ice broke ups temperatures rose, and southerly wind gusts 35 mph pushed the ice ofshore.

Te ability to orecast and predict ice covers important or recreation saety and rescueforts. It is also necessary or winter navigationnd predicting Great Lakes ecosystem impactsuch as lake circulation, water level variability,nd biological lie in the Great Lakes.

GLERL scientists have developed a computer model or LakeErie to predict ice ormation and break up. Te model willbe incorporated into the GLERL-developed Great LakesCoastal Forecasting System, which is now used operationally by the National Weather Service in orecasting circulation,emperature, and wave conditions in Lake Erie. Adding ance orecasting capability to this existing system will better

predict ice concentration and thickness, and improve winterwave orecasts, as ice cover signicantly afects how suracewaves behave. Te Great Lakes Ice-Circulation Model (GLIM)

will eventually be extended to cover all ve Great Lakes oregional climate change studies.

MODIS Satellite photo showing Lake Erie ice cover on February 8, 2009, 14:03 EST.

 Arctic Sea Ice ResearchTe Arctic Sea has been experiencing record low ice covesince 1995. Strong winds have been increasing the amouo Arctic ice being pushed into the northern Atlantic. Textent o Arctic sea ice reached its all time low in Septem2007, shattering all previous lows since satellite record-keeping began.

 Arctic sea ice and Great Lakes ice variability are relatedbecause they are controlled by the Arctic Oscillation (AO

– also called the North Atlantic Oscillation (NAO) – viathe Icelandic Low pressure system. Generally speaking, th AO in a phase o high or low pressure can afect the ArctOcean and thereore the Great Lakes climate. I the AOproduces a low pressure (positive phase), the Great Lakesexperience a warmer climate, leading to less ice cover, andvice versa.

http://www.glerl.noaa.gov/res/glcfs/glcfs.html

Example of Lake Erie ice concentration forecast map. Maps are available

for forecasts up to 120 hours into the future.