NOAA Great Lakes Environmental Research Laboratory

The latest news and information about NOAA research in and around the Great Lakes


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Five decades of Great Lakes ice cover data – and where to find it

Understanding the major effects of ice on the Great Lakes is crucial. Ice cover impacts a range of societal benefits provided by the lakes, from hydropower generation to commercial shipping to the fishing industry. The amount of ice cover varies from year to year, as well as how long it remains on the lakes. With almost five full decades of ice data to look at, GLERL scientists are observing long-term changes in ice cover as a result of climate change. Studying, monitoring, and predicting ice coverage on the Great Lakes plays an important role in determining climate patterns, lake water levels, water movement patterns, water temperature structure, and spring plankton blooms.

Maximum ice cover on the Great Lakes every year from 1973 to 2018. Credit: NOAA GLERL.

NOAA GLERL has been exploring the relationships between ice cover, lake thermal structure, and regional climate for over 30 years through the use of historical model simulations and observations of ice cover, surface water temperature, and other variables. Weekly ice cover imaging products produced by the Canadian Ice Service (CIS) started in 1973. Beginning in 1989, the U.S. National Ice Center (NIC) produced Great Lakes ice cover charts that combined both Canadian and U.S. satellite imagery. Today, these products are downloaded and processed at GLERL by our CoastWatch program, a nationwide NOAA program within which GLERL functions as the Great Lakes regional node. In this capacity, GLERL uses near real-time satellite data to produce and deliver products that support environmental decision-making and ongoing research. While the Great Lakes CoastWatch Program is a great resource for near real-time ice cover data, historical data is just as important – and that’s where GLERL’s Great Lakes Ice Cover Database comes in. Originally archived by GLERL through the National Snow & Ice Data Center, the Great Lakes Ice Cover Database houses data that dates back to 1973 and continues to be updated daily during the ice season every year.

Ice caves on Lake Michigan’s Glen Haven beach in 2005. Credit: National Parks Service.

Even though the CIS and NIC are the ones who actually collect Great Lakes ice cover data, GLERL plays the important role of re-processing this ice data into more accessible file formats, making it readily usable to anyone who needs it. Agencies and organizations that have used ice cover data from GLERL in the past include the NASA Earth Observatory, U.S. Army Corps of Engineers, U.S. Coast Guard, and National Geographic. Types of data requested might include historic minimum and maximum ice coverage for certain regions or lakes, or dates of the first and last ice cover in a region from year to year. This information can be helpful for managers in industries like energy production and commercial shipping.

This graph shows annual maximum ice coverage on the Great Lakes every year from 1973 to 2020. The red dashed line marks the long-term average maximum ice cover of 53.3%. Credit: NOAA GLERL.

GLERL scientists can also use this historic ice cover data to analyze how current ice cover conditions compare with previous years. For example, here’s how the ice cover during January 2021 stacks up against data for past Januarys:

  • Lake Michigan and the five-lake average had their second lowest January ice cover (with January 2002 being the first lowest).
  • The other lakes are all in the top five lowest ice cover for the month of January.
  • Six out of ten of the Januarys with the lowest ice cover have occurred during the last decade for the five-lake average (though 2014 was fourth highest January ice cover).
This graph shows average Great Lakes ice cover for the month of January every year from 1973 to 2021, organized by lowest ice cover (far left) to highest ice cover (far right). Credit: NOAA GLERL.

GLERL is also working to make this data more user-friendly for anyone looking to utilize it. This recent paper from GLERL and the Cooperative Institute for Great Lakes Research (CIGLR) describes the scientists’ efforts to standardize two existing formats of historic ice cover data. The authors explain that “technology has improved and the needs of users have evolved, so Great Lakes ice cover datasets have been upgraded several times in both spatial and temporal resolutions.” The paper documents the steps the authors took to reprocess the data in order to make it more consistent and accessible, which ultimately makes it easier for users to study long-term trends.

Timeline of ice chart evolution and frequency, from the research paper described above (Yang et al 2020). Credit: Ting-Yi Yang, Cooperative Institute for Great Lakes Research.

Whether you’re looking for decades of Great Lakes ice data or just a few days, GLERL’s got you covered! Looking for more Great Lakes ice cover information? Visit our ice cover homepage here.

MODIS satellite image of ice cover on the Great Lakes, March 16, 2014. Credit: NOAA Great Lakes CoastWatch.


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Scientists are people with questions: a conversation with GLERL limnologist Craig Stow

A man in a baseball cap stands in the GLERL lobby in front of some 3-d bathymetry maps of the Great Lakes

Craig Stow, a GLERL limnologist, says scientists are “people with questions.”

Craig Stow is a Limnologist (that means somebody who studies freshwater systems) at NOAA GLERL. He models nutrients cycling through (Great) lakes. His research is super applicable; notably, he’s part of the team trying to deal with nutrient loads in Lake Erie – he wrestles with the question of how much phosphorous is coming into the lake, and how it gets there.

Read on to see how Craig deals with mental blocks, why science isn’t like the movies, and what he thinks people get wrong about researchers.

How would you describe your job?

“I try to learn about things so that I can usefully apply any enhanced insight I might gain. Currently I’m trying to better understand the separate influences of tributary flow and tributary nutrient concentration on nutrient loads to Lake Erie. We have set new phosphorus load targets and those can be achieved by managing tributary flow, tributary nutrient concentration, or both, but the effects in the lake will differ in ways that are not obvious.”

What is the most interesting thing you’ve accomplished?

“The most interesting things are those that are counter to what you expect a priori. Though it can take a while to come to grips with the realization that you didn’t know what you were talking about at the outset. When I was a master’s student my adviser told me it was good to be humbled; I didn’t expect it to happen so frequently. Astounding revelations are more prevalent in movies than real life — at least in my office. Most of what I accomplish involves incremental insights that nudge the field along.”

Where do you find inspiration? Where do your ideas come from in your research or other endeavors in your job?

“Read a lot, talk to colleagues, recognize unresolved tensions, think really hard, then do something else. Good insights often occur when your mind relaxes following a period of intense concentration.”

How would you advise high school students interested in science as a career path, or someone interested in your particular field?

“Learn to write well. Publishing requires recognizing a good story and telling it effectively. If you can’t express your thoughts clearly and succinctly you will struggle in this field.”

What do you like to do when you AREN’T sciencing?

“I like to play and listen to music, work outdoors, be at home with the family, and grill. And think about fishing. I used to actually go fishing, now I just think about it. I’m usually more successful and don’t jab the hook in my fingers as often.”

What do you wish people knew about scientists or research?

“Science is the collective process of searching for the truth. It occurs by assembling and synthesizing information to generate ideas, and sharing those ideas so that others can corroborate, contradict, or modify them. The peer-reviewed literature is the primary venue for that process; that’s why publication is important. Scientists are the individuals who participate in this process. Most are intrinsically curious, many are really smart, some live an illusion of objectivity, and there are a few charlatans. The successful ones are more tenacious than anything else. There’s a tendency to view scientists as people with answers, mostly they’re people with questions.”