NOAA Great Lakes Environmental Research Laboratory

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


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Update on Lake Erie hypoxia forecasting stakeholder workshop (May 23, 2017)

Researchers partner with drinking water plant managers to forecast hypoxia in Lake Erie

By Devin Gill, Cooperative Institute for Great Lakes Research and Kristin Schrader, Great Lakes Observation Systems

Lake Erie’s “dead zone” not only impacts the lake’s ecosystem, but also poses challenges for managers of drinking water treatment facilities. The Lake Erie dead zone is a region of the central basin where oxygen levels within the water become extremely low, creating a condition known as hypoxia. Great Lakes researchers are sharing their scientific expertise to help managers be fully prepared for threats to drinking water resulting from hypoxic conditions.

Scientists from NOAA GLERL, Cooperative Institute for Great Lakes Research (CIGLR) and the Great Lakes Observing System (GLOS) met on May 23 in Cleveland, Ohio with water plant managers from the southern shore of Lake Erie for a stakeholder engagement workshop to discuss the hypoxia issue. An important focus of the workshop was the development of a new hypoxia forecast model that will act as an early warning system when hypoxic water has the potential to enter intakes of water treatment facilities. The depletion of oxygen in hypoxic water occurs when the water column stratifies (separates into warm and cold layers that don’t mix). Oxygen in the lower, cold layer becomes depleted from the lack of mixing with the upper (warm) layer that is exposed to air, as well as from the decomposition of organic matter (dead plants and animals) in the lower layer. The process of hypoxia is illustrated by GLERL’s infographic, The Story of Hypoxia.

Stakeholders who attended the workshop explained that water treatment operators must be prepared to respond quickly during a hypoxic event to ensure that drinking water quality standards are met. Hypoxic water often is associated with low pH and elevated manganese and iron. Manganese can cause discoloration of treated water, while low pH may require adjustment to avoid corrosion of water distribution pipes, which can introduce lead and copper into the water.

At the workshop, researchers shared information on lake processes that contribute to hypoxia and on development of the Lake Erie Operational Forecasting System that provides nowcasts and forecasting guidance of water levels, currents, and water temperature out to 120 hours, and is updated 4 times a day. Information was also shared on preliminary hypoxia modeling results that simulated an upwelling event (wind-driven motion in the Great Lakes, pushing cooler water towards the lake surface, replacing the warmer surface water) that brought hypoxic water to several water plant intakes in September, 2016. Water plant managers reported that advance notice of a potential upwelling event that could bring hypoxic water to their intakes would be useful to alert staff and potentially increase the frequency of testing for manganese.

Dr. Mark Rowe from University of Michigan, CIGLR, researcher and co-lead on this initiative, comments on the value of this hypoxia stakeholder engagement workshop: “At both NOAA and the University of Michigan, there is an increasing focus on co-design of research, which refers to involving the end-users of research results throughout the entire project, from concept to conclusion. If we succeed, a new forecast model will be developed that will be run by the operational branch of NOAA. This can only happen if there is a group of users who request it. This workshop provided critical information to the researchers regarding the needs of the water plants, while also informing water plant managers on how forecast models could potentially help them plan their operations, and on the latest scientific understanding of hypoxia in Lake Erie. ”

Stakeholder Scott Moegling, Water Quality Manager at City of Cleveland Division of Water, also recognizes the value of  engagement between the stakeholders and the Great Lakes researchers. Moegling points out that “the drinking water plant managers not only benefit from sharing of operational information and research, but also by establishing lines of communication between water utilities and researchers that help identify common areas of interest. The end result—researchers providing products that can be immediately used by water utilities—is of obvious interest to the water treatment industry on Lake Erie.”  Moegling also views the GLERL/CIGLR research on the hypoxia forecast model as holding great potential in predicting hypoxic conditions in Lake Erie and believes that once the model is developed and calibrated, there may be a number of other possibilities for highly useful applications.

In addition to sharing the latest research on hypoxia, the stakeholder engagement workshop provided a forum for water plant managers to share information with each other on how to recognize hypoxic events and efficiently adjust water treatment processes. Researchers at CIGLR and NOAA GLERL are committed to conduct research that serves society, and will continue to work with this stakeholder group over the course of the five-year project to develop a hypoxia forecast model that meets their needs.

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Tracking Changes in Great Lakes Temperature and Ice: New Approaches

In a new study, scientists from GLERL, the University of Michigan, and other institutions take a new look at changing ice cover and surface water temperature in the Great Lakes. The paper, set to be published in Climatic Change, is novel in two ways.

While previous research focused on changes in ice cover and temperature for each lake as a whole, this study reveals how different regions of the lakes are changing at different rates.

While many scientists agree that, over the long term, climate change will reduce ice cover in the Great Lakes, this paper shows that changes in ice cover since the 1970s may have been dominated by an abrupt decline in the late 1990s (coinciding with the strong 1997-1998 winter El Niño), rather than gradually declining over the whole period.

NOAA tracks ice cover and water surface temperature of the Great Lakes at a pretty fine spatial scale. Visit our CoastWatch site and you’ll see detailed maps of surface temperature and/or ice cover updated daily.

However, when studying long-term changes in temperature and ice cover on the lakes, the scientific community has used, in the past, either lakewide average temperature data or data from just a few buoys. We knew how each lake was changing overall, but not much more.

Now, for the first time, researchers are using our detailed data to look at the changes happening in different parts of each lake.

Using GIS (geographic information system) analysis tools, researchers calculated how fast ice cover and temperature were changing on average for each of thousands of small, square areas of the lakes (1.3 km2 for ice cover, and 1.8 km2 for temperature).

The maps below show the results. Changes in ice, on the left, are reported in the number of days of ice cover lost each year. Temperature changes are reported in degrees Celsius gained per year.

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Panel a shows the change in seasonal ice cover duration (d/yr) from 1973 to 2013, and panel b shows the change in summer surface water temperature (°C/yr) from 1994 to 2013. Maps from Mason, L.A., Riseng, C.M., Gronewold, A.D. et al. Climatic Change (2016). doi:10.1007/s10584-016-1721-2. Click image to enlarge.

The researchers also averaged these values across major subbasins of the lakes. Maps of those results are below. The color coding is the same, and again, ice cover is on the left while temperature is on the right.

Note: These subbasins aren’t random, and were outlined by scientists as a part of the Great Lakes Aquatic Habitat Framework (GLAHF), which is meeting a need (among other things) for lake study at intermediate spatial scales.

The panel on the left shows the change in seasonal ice cover duration (d/yr) from 1973 to 2013, and the panel on the right shows the change in summer surface water temperature (°C/yr) from 1994 to 2013. Maps created by Kaye LaFond for NOAA GLERL. Click image to enlarge.

Depth, prevailing winds, and currents all play a role in why some parts of the lakes are warming faster than others. A lot of information is lost if each lake is treated as a homogenous unit. With so much variation, it may not make sense for every region of the Great Lakes to use lakewide averages. Studying changes at a smaller scale could yield more useful information for local and regional decision makers.

The second part of the story has to do with how ice cover has changed in the lakes. Previous studies typically represent changes in ice cover as a long, slow decline from 1973 until today (that would be called a ‘linear trend’). However, when looking at the data more carefully, it seems the differences between the 70’s and today in many regions of the Great Lakes are better explained by a sudden jump (called a ‘change point’).

The figure below shows yearly data on ice cover for the central Lake Superior basin. It is overlaid with a linear trendline (the long, slow decline approach) as well as two flat lines, which represent the averages of the data before and after a certain point, the ‘change point’.

Annual ice cover duration (d/yr) for the central Lake Superior basin, overlaid on the left with a linear trend-line, and overlaid on the right with a change-point analysis. Graphic created by Kaye LaFond for NOAA GLERL. Click image to enlarge.

Statistical analyses show that the change point approach is much better fit for most subbasins of the Great Lakes. 

So what caused this sudden jump? Scientists aren’t sure, but the change points of the northernmost basins line up with the year 1998, which was a year with a very strong winter El Niño. This implies that changes in ice cover are due, at least in part, to the cyclical influence of the El Niño Southern Oscillation (ENSO).

All of this by no means implies that climate change didn’t have a hand in the overall decline, or that when there is a cyclical shift back upwards (this may have already happened in 2014) that pre-1998 ice cover conditions will be restored. The scientific consensus is that climate change is happening, and that it isn’t good for ice cover.

This research just asserts that within the larger and longer-term context of climate change, we need to recognize the smaller and shorter-term cycles that are likely to occur.