Great Lakes Water Levels Sensitive To Climate Change

Great Lakes Water Levels Sensitive To Climate Change

ScienceDaily (Jan. 14, 2009) — The water level in the Great Lakes has varied by only about two meters during the last century, helping them to play a vital role in the region's shipping, fishing, recreation and power generation industries.

But new evidence by scientists from the University of Rhode Island and colleagues in the U.S. and Canada, published recently in the journal Eos, indicates that the water level in the lake system is highly sensitive to climate changes.

"In the distant past, there were great fluctuations in the water level of the Great Lakes, but it was thought to have been related entirely to the advance and retreat of the glaciers," said URI geological oceanographer John King, who led the study with URI visiting scientist Michael Lewis, emeritus scientist with the Geological Survey of Canada. "But the last time lake levels fell dramatically – down to 20 meters below the basin overflow outlets – it was due to dry climate conditions."

That event, which occurred between 7900 and 7500 years ago in the early Holocene period, caused the lakes to become disconnected as their overflow rivers, including the Niagara River, ran dry.

"People used to say that the oceans are so big, we can dump whatever we want in them and nothing will happen," said King. "They thought of the Great Lakes in the same way, that the system is too large to be sensitive to climate variations. But now we know that to be untrue. We've demonstrated that at least once in the last 10,000 years, climate drove the lake levels down pretty substantially."

Researchers had long assumed that the Great Lakes had been "hydrologically open" and connected since their formation 16,000 years ago during the retreat of the last ice sheet, but recent evidence has found this to be false. Ancient shorelines, submerged beaches, and tree stumps on the floor of some lakes indicate that the water line had been as much as 20 meters below the present lake level."We had a multi-proxy approach to this study, and through many lines of evidence we identified this as a dry interval with a climactic cause as opposed to a glacial-related cause," King said.

The climate and water levels in the Great Lakes region are determined by the interplay of three air masses: dry, cold Arctic air from the North, dry warm Pacific air from the West, and warm, moist tropical air from the Gulf of Mexico. The scientists found that during the period when lake levels receded significantly, the dry air from the Arctic and Pacific was dominant. Later, when precipitation from the tropical air mass became more frequent, the Great Lakes began to flow from one to another as they do today.

King worries about the economic impact to the Great Lakes region if the present climate changes lower water levels significantly. Navigation, water usage and hydropower would be severely affected.

"The climate interval that occurred back then is different from what we're going through now," King said. "It would take a pretty big change to close the basins again. But the sorts of temperatures and precipitation amounts that happened then are within the range of what is predicted for 2100. In the worst-case scenarios, a lot of things become possible.

"The range of lake-level changes that are likely to happen in the next 100 years is probably larger than the range of levels observed during the last century," he added.

WEATHER NOTE

Study links swings in North Atlantic oscillation variability to climate warming

Using a 218-year-long temperature record from a Bermuda brain coral, researchers at the Woods Hole Oceanographic Institution (WHOI) have created the first marine-based reconstruction showing the long-term behavior of one of the most important drivers of climate fluctuations in the North Atlantic.

The North Atlantic Oscillation (NAO) is a wide-ranging pressure seesaw that drives winter climate over much of North America, Europe and North Africa. Past reconstructions of the NAO have relied mainly on terrestrial, or land-based records, such as tree ring chronologies combined with ice cores and historical climate data. Those records do not fully capture oceanic processes linked to NAO variability, and short instrumental records from relatively few locations limit the understanding of ocean-atmosphere dynamics with regard to NAO behavior.

"By analyzing the coral, we were able to look at changes in the ocean relative to changes on land," said Nathalie Goodkin, lead author of the study published in the December issue of the journal Nature Geoscience. "Because they are slow growing and have long life-spans, corals can provide high resolution records that are well dated and centuries long."

As they grow, corals accrete seasonal and annual growth layers, similar to tree rings. The proportions of trace elements versus the major element (calcium) found in the layers of the skeleton largely depend on the temperature of the seawater in which it was formed. By analyzing the strontium to calcium ratio in the Bermuda brain coral, Goodkin and colleagues - WHOI scientists Konrad Hughen, Scott Doney and William Curry - were able to reconstruct monthly changes in ocean temperatures and evaluate variability of the NAO during both cold and warm periods from the Little Ice Age (1800�) to modern day.

The research team found the variability of the NAO decade-to-decade (multi-decadal scale) has been larger, swinging more wildly, during the late twentieth century than in the early 1800s, suggesting that variability is linked to the mean temperature of the Northern Hemisphere. This confirms variability previously reported in past terrestrial reconstructions.

"When the Industrial Revolution begins and atmospheric temperature becomes warmer, the NAO takes on a much stronger pattern in longer-term behavior," said Goodkin. "That was suspected before in the instrumental records, but this is the first time it has been documented in records from both the ocean and the atmosphere."

Safe driving in severe weather

The recent heavy frost will no doubt return again and again over the winter and early spring. Here is some advice for safer driving in severe weather:

* Drivers are reminded that rain and spray can reduce visibility and when the road is wet it can take up to twice as long to stop, so it makes sense to slow down when it's raining.

* Surface water may affect motorways and major A roads so we advise drivers to move slowly through any standing water and test their brakes once they're through before continuing to drive.

* High-sided vehicles are particularly affected by windy weather but strong gusts can also blow any vehicle, cyclist, motorcyclist, or horse rider off course. This can happen on open stretches of road exposed to strong crosswinds, or when passing bridges and high-sided vehicles.

* Plan journeys. Check the weather forecast, road conditions, and the route for delays before leaving home and delay travelling if the weather becomes severe.

* Drivers are also advised to carry warm clothing and an emergency pack, which includes food and water, boots, de-icer, a torch, a spade if snow is forecast, and to make sure they have plenty of fuel for the journey.

MARITIME NOTE

Time to reboot maritime’s image, retired New Orleans port exec says

Retired port executive Ron Brinson said the Charleston maritime community should take the rapt attention that Maersk’s decision to leave has thrust on the port and turn it into a better understanding of the industry.

“The public does not understand and does not appreciate the value of the port,” Brinson said Thursday to a crowded room at the Charleston Motor Carriers Association’s monthly luncheon at the Sheraton in North Charleston.

Because of that misunderstanding, Brinson said, “we have a port that has been competing with one hand tied behind its back.”

Brinson, now living in Charleston, retired from the business in 2003 after more than 15 years as president and CEO of the Port of New Orleans. A former newspaper editor and reporter in Charleston, Brinson also worked for the S.C. State Ports Authority before leaving for Louisiana.

Much of Brinson’s talk focused on the fallout caused by Maersk Line’s announcement that it would begin pulling services out of Charleston early this year and completely leave town when its contract expires at the end of 2010.

Although the Danish company’s business is extremely important to Charleston and the entire state, the community should not take the news personally, Brinson said.

“These are unemotional business decisions that we sometimes tend to make emotional,” Brinson said.

Charleston, he noted, isn’t the first community to deal with the loss of Maersk, the world’s largest steamship line and the S.C. State Ports Authority’s largest customer.

In 1999, Maersk left the Port of Long Beach in California because officials there could not or would not agree to concessions the shipping company said it needed.

It took about three years, but Long Beach recovered after losing 25% of its business to competitor Los Angeles.

Brinson also warned the group not to heap blame on the International Longshoremen’s Association. Anti-union sentiment seems to have grown stronger nationally in the wake of Detroit’s struggles, he said, and seems even more intense in Southern states, including South Carolina.

The Maersk decision also compounded those feelings because the company said it was moving because the ILA refused to let the company operate from the common-user yard at the Wando Welch Terminal, a move that would have eliminated several dozen union jobs.

People, especially in South Carolina, tend to perceive unions as a four-letter word, he said. “The reality is that unions are a four-letter word at our port, and that word is F-A-C-T.”

In Charleston, he said, union labor has a good reputation. The SPA has a good reputation also, he said, and offered this advice: “Ease up; give the ports authority a little breathing room.”

He had some advice for port executives as well. Brinson said they should be willing to try new operating models and not wait for changes — potentially misguided changes — to be forced upon the port by the General Assembly and governor.

And he suggested that the entire maritime community, including SPA staff members, spend time “rebooting” relationships with the public. If the state is giving off the perception that it does not support its port operations, steamship lines might take the cue and send their business elsewhere.

“Maybe we South Carolinians are sending the wrong message to the marketplace,” he said.

RS