NOAA Great Lakes Environmental Research Laboratory

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

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The tricky business of predicting climate change impacts on Great Lakes water levels

An early online release of GLERL researcher Brent Lofgren’s paper entitled “Physically Plausible Methods for Projecting Changes in Great Lakes Water Levels Under Climate Change Scenarios” can be found on the American Meteorological Society’s Journal of Hydrometeorology website.

In the paper, Dr. Lofgren and his co-author, Jonathan Rouhana, explore two different ways to model the effects of climate change on evapotranspiration (the movement of water from the land to the atmosphere as the combined result of evaporation and transpiration), and, subsequently, on the water levels of the Great Lakes.

Predicting how climate change will affect the water levels of the Great Lakes is a tricky business. To answer questions like this, it is often best to use models. Modeling is central to what scientists do, both in their research as well as when communicating their explanations. Within their models, scientists study relationships between variables in nature and then apply those relationships to possible future scenarios with one or more tweaked variables.

However, earth systems are so complex and have so many moving parts, that it’s almost impossible to capture them completely in an equation or series of equations. The beauty of modeling, is that it allows scientists to start with a small amount of data and, as time goes on, to build up a better and better representation of the phenomenon they are explaining or using for prediction.

Sometimes, particularly when modeling climate change, problems arise with so-called empirically-based models. Empirically-based models are created by making observations about two or more variables over a certain time period and under certain conditions, and inferring relationships from those observations. Often, those models don’t hold up when conditions change.

An alternative is physically-based models, which use the laws of physics (like conservation of mass, energy, etc.) to make predictions. Complexity is still a hurdle, but the laws of physics hold up no matter what—even when the climate changes.

Dr. Lofgren’s paper details issues with an empirically-based model widely used in Great Lakes research, the Large Basin Runoff Model (LBRM). From the abstract:

This model uses near-surface air temperature as a primary predictor of evapotranspiration (ET); as in previous published work, we show here that its very high sensitivity to temperature makes it overestimate ET in a way that is greatly at variance with the fundamental principle of conservation of energy at the land surface. The traditional formulation is characterized here as being equivalent to having several suns in the virtual sky created by LBRM.

Several suns in the sky – wow! In the most extreme case, this method of calculating evapotranspiration behaves as though there were 565 suns. 

In the context of climate modeling, “The LBRM oversimplifies the physics of the interaction between the earth and the atmosphere,” says Dr. Lofgren.

This doesn’t mean the LBRM isn’t useful in specific instances (e.g. short-term forecasting), or that you shouldn’t ever trust empirically-based models. It just means that different types of models have their place in different circumstances, and that the LBRM probably isn’t the best choice for modeling hydrologic response under climate change conditions.

Scientists often argue about the rightness of their model, and in the process, the model can evolve or even be rejected. Consequently, models are central to the process of knowledge-building.

Scientists who dare to create models know that their models will be scrutinized and tested. Research like Dr. Lofgren’s ensures not only that models are used appropriately with an acknowledgment of their limitations, but that they are continually improved upon.


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Working to understand the drivers of bloom toxicity in Lake Okeechobee

IMG_0207Last week, GLERL scientist Tim Davis spent time down in Florida sampling and conducting field experiments in Lake Okeechobee and the St. Lucie River, two major freshwater ecosystems in Florida that are currently under a state of emergency due to the presence of harmful algal blooms.

IMG_0197The sampling and research we’re doing in Lake Okeechobeeo helps us get a better understanding of the environmental drivers behind changes in bloom toxicity—a main focus of the research we’re doing within our HAB research program. The work we’re doing throughout western Lake Erie, has led the creation of an experimental Lake Erie HAB Tracker and Lake Erie Experimental HAB forecast, which are used by water treatment managers and others to make important decisions about water quality in the region. 

This collaboration with CILER (Cooperative Institute for Limnology and Ecosystems Research), Stony Brook University and USGS, will prove beneficial to the continued research and better understanding of ecosystem health effects related to human-influenced water quality degradation, not only in the Great Lakes, but throughout all large freshwater systems. By comparing the genetic characteristics of the blooms in Florida to those that occur in Lake Erie, we hope to not only better understand toxicity, but also whether or not we can apply the same techniques of forecasting and monitoring in Lake Erie to other large bodies of freshwater around the world.

GLERL will continue to receive bloom samples for genetic testing of the Lake Okeechobee HAB for the rest of the season.  

Note: For specific information about the bloom in Florida, please visit 
the responding agencies' website: 

For sampling information please visit Florida Department of
Environmental Protection:

For health information please visit Florida Department of

For information on water management in the region please
visit South Florida Water Management District:

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2016 Lake Erie HABs Forecast Has Arrived

Earlier today, NOAA and partners released their forecast of Harmful Algal Blooms (HABs) for the summer of 2016. The official predicted bloom severity came in at a 5.5, far milder than last year’s 10.5, although still significant.

This spring has been relatively dry, sporting a 4 inch rain deficit since May 2016, and flows in the Maumee River are down. Consequently, the amount of total bioavailable phosphorus flowing into Lake Erie that could feed blooms is lower than the past three years.

This doesn’t mean the source of the nutrients – mainly agricultural runoff – has been addressed. Heavy, intense rainfall in the future could pick up excess nutrients and create severe blooms again.

There is a high uncertainty associated with this summer’s forecast (ranging from 3 to 7) because we don’t know for sure what the overwinter effect from last summer’s bloom is going to be — phosphorous and algae material could remain in the water and boost this year’s bloom.


2016 HABs Forecast

NOAA GLERL and partners will be keeping an eye on Lake Erie all summer, and in September, we’ll be sending our Environmental Sample Processor (ESPniagara) on its first mission to monitor algal toxins in real-time near the Toledo water intake.

For more information, check out our new and improved HABs and Hypoxia homepage.