Massive Great Lakes ice and snow cover will boost lake levels in 2014

Benefits of a harsh winter?

I’m an optimist by nature. And maybe a bit of a skeptic too. Is it possible to be both? I think so.

Optimism gets you through a Minnesota winter. A little healthy skepticism helps when you are looking at a couple hundred weather maps a day. Some may be on the money. Some will lead you down the garden path in the wrong direction. It’s part of the fascination of being a meteorologist. And you better have a darn good BS detector. But I digress.

When I hear Minnesotans complain about the most severe winter in 35 years, the optimist in me knows there’s an upside to all that cold and snow — even as I feel the sting of cold like everybody else and the pain in my back from yet another round of shoveling and “roof raking.”

A good cold snowy winter is good for Minnesota, I keep telling myself.

One benefit of the most severe winter in 35 years? More water in Lake Superior and other Great Lakes.

Image: Lake Superior Maritime Museum

Great Lakes water levels have approached record lows in recent years. The massive ice cover prevents wintertime evaporation. Deep winter snow pack fuels massive spring runoff, and boosts water levels in the Great Lakes. Both factors will contribute to higher water levels in 2014.

Here’s the story from NOAA.

More ice cover may lead to higher water levels

Near record level ice cover topping 90 percent recently over the Great Lakes could help reduce evaporation and contribute to higher lake levels. NOAA and the U.S. Army Corps of Engineers this week forecast that Great Lake water levels will be closer to average over the next six months and higher than last year on most of the lakes. A similar pattern occurred in 1996 when the Great Lakes experienced severe ice cover of more than 80 percent. Water levels were higher in 1997 on all but Lake Superior where they were largely unchanged.  To get the latest ice cover click here. To learn more about how Great Lakes ice affects water levels click here.

Image: NOAA

As people who live along our nation’s coast experience rising sea levels, residents along the Great Lakes – the Earth’s largest lake system – are adapting to the opposite problem: chronic low water levels and a receding shoreline.

In a perspective now running in Science magazine, Drew Gronewold, a hydrologist at NOAA’s Great Lakes Environmental Research Laboratory, says “the record low water levels in Lake Michigan-Huron in the winter of 2012 to 2013 raise important questions about the driving forces behind water level fluctuations and how water resource management planning decisions can be improved.” 

Ice cover on western Great Lakes on March 5th 2014. Image: NASA MODIS

Ice, evaporation and water levels

Here’s another look at how ice cover affects lake levels on the Great Lakes.

When a severe winter brings extensive ice cover to the Great Lakes,
questions arise about potential impacts on water levels. Does more ice
cover lead to higher water levels because of decreased evaporation?
This is not a simple question, due to the complex relationship between
these factors and the massive surface areas over which they interact in
the Great Lakes. NOAA-GLERL has been exploring these relationships for
over 30 years through development of model simulations and analysis
of observations of ice cover, over-lake evaporation, surface water
temperature, and lake levels.

Note that the majority of evaporation on each lake occurs before
the onset of ice. It is likely that this winter’s severe ice cover may impact
the thermal structure of the Great Lakes through 2014, potentially
causing lower water temperatures that will lead to less evaporation during
the fall of 2014. Combined with this year’s above average snow pack and
increased spring runoff, it is not entirely unlikely that water levels could
begin to approach their long-term average on Lakes Michigan and Huron
in the next year

Eastern storm winds up

How about some more heavy wet snow and eventual spring runoff for the Great Lakes? The next storm winds up in Chicago overnight and shoots east thorough Detroit, Cleveland, Buffalo and northern New England.

Image: NOAA

Chicago has piled up a whopping 75.5 inches of snow so far this winter, and this latest storm may get them close to the all time record. here’s more from the Chicago NWS Facebook page.

Chicago needs about 14 inches of snow before June 30th to set the record for most snow in a season (Fall-Winter-Spring). Some computer forecast models are hinting this could be possible tonight alone, but we are hanging onto the more likely 4-8″ range for much of the area. Smaller-scale atmospheric effects could boost local totals, but those effects tend to be fairly short-lived and are tough to pin down very far in advance. We’ll have updated winter weather headlines available later this afternoon, including a decision about how to handle the watch in southern portions of our forecast area.

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 Minnesota roller coaster

Welcome to March in Minnesota.

The Upper Midwest rides an undulating jet stream the next two weeks. That means a series of cool and warm fronts sweeping through every couple of days, and some sharp temperature swings.

Image: Weatherspark

We spend several days above freezing and many nights below freezing in the next week. That’s a good recipe for a nice slow snow melt that can minimize flood risk.

Here’s the latest flood outlook from the Twin Cities NWS.


Doubling CO2: How ‘sensitive’ is earth’s climate to future CO2 rises?

Here’s an illuminating story from on how we can best gauge just how sensitive our climate is to CO2 changes.

Scientists say that doubling pre-industrial carbon dioxide levels will likely cause global average surface temperature to rise between 1.5 and 4.5 degrees Celsius (2.7 to 8.1 degrees Fahrenheit) compared to pre-industrial temperatures. (Current concentrations are about 1.4 times pre-industrial levels.) The full process could take hundreds of years — perhaps more than a thousand—to play out.  Climate scientists call the full temperature rise from doubled carbon dioxide concentrations the equilibrium climate sensitivity.

To understand how sensitive the climate is to carbon dioxide on time frames of a century or less, scientists also study the transient climate sensitivity. They imagine that carbon dioxide will continue to increase at roughly the rate it has been, and then ask how much warming would be realized around the time when the concentration has doubled the pre-industrial value. On this shorter time scale, it’s likely the planet will warm between 1 and 2.5 degrees C (2 and 4.5 degrees F).

The difference between transient and equilibrium sensitivity comes from the fact that some parts of the Earth system — mountain glaciers, sea ice, precipitation — react within years or a few decades to a warming or cooling nudge. Others — including ice sheets, permafrost, and especially the deep ocean — respond sluggishly, sometimes taking centuries to overcome the inertia of their previous state.

Atmospheric carbon dioxide concentrations in parts per million for the past 800,000 years, based on EPICA (ice core) data, with the 2013 annual average concentration of 396.48 ppm (dashed line) appended. The peaks and valleys in carbon dioxide levels follow the coming and going of ice ages (low levels) and warmer inter-glacials (higher levels). NOAA, based on EPICA Dome C data (Lüthi, D., et al., 2008) provided by NOAA NCDC Paleoclimatology Program.

“Sensitivity” is not a prediction of future temperatures

Estimates of climate sensitivity are not the same thing as model predictions of future temperatures.  Sensitivity is a way to try to describe how the Earth system is capable of reacting if atmospheric carbon dioxide concentrations were to double, not a prediction of if or when that might happen. Future temperatures depend, obviously, on how sensitive the climate is to carbon dioxide and how much we actually emit.

Preliminary data for 2013 show that the annual average carbon dioxide concentration was around 396 parts per million (ppm). In recent years, carbon dioxide concentrations have been growing at a rate of 2 to 2.5 ppm each year.  At those rates, it would take 60 to 80 years to double the pre-industrial level of 275 ppm. However, the rate of increase over the past half century has not been steady; it’s been accelerating by about 0.5 ppm per year per decade.  If the acceleration continues into the future, then doubled pre-industrial carbon dioxide concentrations will be reached in about 50 years.