Satellite view of the southern half of Lake Michigan Friday, one day before the ice extent record was set. (NASA)

On Saturday, 93.29 percent of Lake Michigan was covered by ice, the most in records dating back to 1973.

This extent bested the previous record of 93.1 percent set in 1979.

Related: Lake Michigan Ice Cover Reaches Record Coverage! (National Weather Service)

The ice levels rose steadily December and January before sharply falling in late February.  But in early March, following an arctic blast, they surged to Saturday’s peak level.

Time series showing lake ice cover over Lake Michigan this winter (NOAA)

Ice cover across the Great Lakes collectively this winter has reached historic levels.  On Thursday, ice covered 92.19 percent of the Great Lakes, second most on record.

Snow-covered fields appear as geometric patterns on Lake Michigan’s Washington Island in this photograph taken by the crew of the International Space Station. (NASA)

This winter’s Great Lakes ice cover runs counter to the long-term trend, which is in a steep decline.  As Jeff Masters explains at Weather Underground:

The long-term trend in recent decades is sharply downward; Great Lakes ice cover declined 71% between 1973 – 2010. A 2012 study published in the Journal of Climate by researchers at NOAA’s Great Lakes Environmental Research Laboratory found that the biggest loser of ice during the 1973 – 2010 time period was Lake Ontario, which saw an 88% decline in ice cover. During the same time period, Superior lost 79% of its ice, Michigan lost 77%, Huron lost 62%, and Erie lost 50%. The loss of ice is due to warming of the lake waters. Winter air temperatures over the lower Great Lake increased by about 2.7°F (1.5°C) from 1973 – 2010, and by 4 – 5°F (2.3 – 2.7°C) over the northern Lakes, including Lake Superior.

This winter’s snow and ice bonanza in the Great Lakes is a positive for their water levels, which have been well below normal in recent years.  The Associated Press discusses how rising waters may reverse some of the economic hardships associated with depleted levels over the last decade or so:

The prolonged slump hammered the shipping industry, forcing vessels to carry lighter loads to avoid scraping bottom in channels and ports. Marina owners lost money as slips were too shallow for boats to dock. Vegetation sprang up along waterfronts, frustrating hotel and cottage owners.

But the last 14 months have seen a long-awaited comeback, fueled by plentiful snow and rain. Superior and Michigan-Huron’s seasonal rises were almost double their average gains in 2013.

And the signs continue pointing upward. The snow’s water content is the highest in a decade on Lakes Superior, Michigan and Huron.

While water rises will benefit Great Lakes tourism and commerce, there’s concern about possible flooding from rains and melting snow and ice this spring.

“The towering snowpack rimming the watershed will melt this spring and much of the water will flow into the lakes or the streams that feed them,” reports the AP. “The runoff is expected to be so bountiful that some areas will be in danger of flooding, a prospect that could be worsened by ice jams on swollen rivers.”