New images that came in from the NASA Earth Observatory revealed the staggering ice cover that has accumulated over the Great Lakes this winter. The Great Lakes, which is the largest group of freshwater lakes in the world, is seen almost entirely frozen in the images NASA captured using its Aqua satellite. When the satellite took these pictures on February 19, over 80 percent of the five lakes were covered by thick ice, according to the Great Lakes Environmental Research Laboratory (GLERL), which comes under the National Oceanic and Atmospheric Administration.
For the first time in two decades, since 1994 to be precise, ice cover on the Great Lakes hit 88 percent earlier this month. According to NASA’s Earth Observatory, the average ice cover recorded in the Great Lakes is a little over 50 percent and only once in a while the cover crosses the 80 percent mark. The winter ice over the lakes has exceeded the 80 percent mark only five times in the last four decades.
Persisting cold temperatures, which have been blamed on the meandering North Atlantic Jet Stream, have a huge role to play in this year’s excessive ice cover. But, clouds, wind and snow, which cryospheric scientist Nathan Kurtz classified as secondary factors, are also responsible. Some lakes among the Great Lakes have frozen more than others: Lake Erie, Lake Huron and Lake Superior are fast approaching 100 percent ice cover, while Lake Michigan and Lake Ontario are covered around 60 percent and 20 percent respectively. These percentages are based on the latest update from GLERL.
The effect of the massive ice covering the Great Lakes can be felt in the environment of the surrounding region. The director of Michigan Technological University’s Great Lakes Research Centre, Guy Meadows thinks the thick ice could virtually shut down the “lake-effect” snow that is typical around the lakes. The lake-effect snow depends on the capacity of winds blowing from the north and the west to pick up moisture while they move over lake surfaces. If the lake is almost free of ice cover, the winds pick up a lot of moisture and then dump huge quantities of snow on the lake’s eastern and southern shores. But with NASA images showing the Great Lakes almost entirely frozen this season, the effect has been generally less pronounced.
The technology used by NASA to distinguish ice from water, snow and clouds combines shortwave infrared, near infrared and red wavelengths to piece together a false-color image. The elements above appear white in images with visible-wavelength. The false-color image, on the other hand, is capable of isolating ice and creating well-defined images of its extent. In this kind of image, the thicker the ice cover, the more blue it appears. Water, meanwhile is depicted in navy blue; clouds appear either blue-green or white; and snow looks blue-green, according to the Earth Observatory. Very highly detailed, the images even show the shipping lanes that were carved by icebreakers that let cargo vessels carrying essentials to pass through the lakes.
The silver lining to all this ice cover is that it presents great prospects for reviving the Great Lakes’s water levels, which dropped down to record lows in 2013. The ice covering the water beneath is so thick that evaporation can be considered suspended for the near future. The ice cover has kicked up renewed interest in the Great Lakes, with the Apostle Island’s ice caves being opened for visitors for the first time since 2009.
According to Meadows, the freezing lakes will also be able to better support the spawning beds of white fish and some other delicate species of fish from harsh winter storms. In the end, the Great Lakes freezing almost entirely as seen in the NASA images, may prove to be more beneficial than not, given the projected impact on water levels.
By Aruna Iyer