Thursday, January 24, 2013

The Power of Ice

2010 ice shove on Lake Winnebago, Oshkosh WI

In Wisconsin we should know better, but we forget that ice is power.  Our lakes like to remind us of this, with crystalline beauty and crushing power of ice with wind at its back.  Winnebago was gouged out by the Green Bay Lobe of the Wisconsin Glacier.  That sheet of ice made the bathtub that is our lake, and as the ice sat there it dammed what we know as the Fox River and created glacial Lake Oshkosh which spread across the landscape.  As fine sediment dropped out of the water of that lake, it created a flat lake bed of clay and silt which is what Oshkosh and much of Winnebago County is.  My house is on the bottom of a lake.  When the glacier receded, Glacial Lake Oshkosh drained out the Fox River to Lake Michigan, and the deep basin filled up as Lake Winnebago, and so the landscape we know was formed. 

The ice on the lake this winter is barely a foot thick child of the mile high monster that carved out the lake, but it is still a force to be respected.  Water has the most peculiar of traits.  As it forms a solid by cooling it gets larger, unlike everything else we experience.  It only expands a little, but over the span of miles it adds up.  It also expands with tremendous force.  Think of the expansion of water into ice bursting through iron pipes.  Ice is a nearly unstoppable force to be reckoned with.       
Ice can be brutal, but to many it is a source of delight as it is danger.  Snowmobiling, ice fishing, walking, ice skating, hockey, or just running and sliding are a few of the activities to enjoy on the ice.  Ice provides everyone access to the lake.  Fishermen without boats are no longer confined to the shore, docks or bridges.  They can wander out onto the lakes with a bucket and the most simple of fishing gear.   Ice does not discriminate based on one’s economic standing.  Thin ice or cracks can swallow up an SUV or a person on foot just as easily, and every year someone goes down and all too often does not come back up. 
Little icebergs, Lake Winnebago Oshkosh, Wi

Like everything to do with lakes, ice is controversial.  For over a hundred years the water level of the Winnebago system is drawn down throughout the winter to make way for the snow smelt and spring rains.  This also has the perceived benefit of reducing ice damage.  While there may be some benefits to shore protection from ice expansion it does little to prevent damage from ice shoves.  Ice shoves on Lake Winnebago can climb uphill, reaching spectacular heights in no time with the right wind, and like miniature glaciers bulldoze everything in their path.  The dams that control water levels cannot physically draw the lake down far enough to prevent this damage, and if they could there would be severe damage to habitat that fish and wildlife depend on.   

On calm nights with the temperature dropping you can hear the ice boom as it contracts and cracks.  Walk along the shore of Menominee park if you are unsure of the ice on one of these nights and you can hear the power building.  The ice is restless.  The constant shifts of temperature changes, the sun, and the wind are always weakening the ice even as it gets thicker.  It can take months for ice to be thick enough to support the weight of a car, but in a few short weeks it degrades and piles up on shore.  Lake ice is something of a troubled teenager struggling to be noticed as it makes its way in the world in the shadow of a famous parent.  It throws tantrums, creates trouble, and then burns out, ends up in rehab, builds up to something delightful, and throws another tantrum.

Previously published in the Oshkosh Scene.  

Tuesday, January 8, 2013

Under a Frozen World

Snowy Wetland
Slough off North Asylum Bay
The lakes and marshes become quiet in the winter when the ice covers the lakes and snow blankets the surrounding marshes, but life continues below ice and snow. 

Tunneling through the snow are a number of little mammals.  Mice, voles, and shrews enjoy the relative safety provided by their tunnels.  There they are free from the piercing eyes of hawks, but are still vulnerable to the ears and talons of great-horned owls and pouncing foxes.
On the lake bottoms are the flying insects of summer.  The billions of lake flies of spring are all there as the larva called bloodworms.  Keeping company with sediment, decaying plants and rocks are the larva of caddisflies, damselflies, dragon flies, and mayflies that will emerge from the lake and take flight in spring and summer.  All of these are food throughout the winter for bluegills, perch and other fish. 

Up the food chain there are reptiles we envision hibernating in the mud.  Some turtles and frogs are indeed buried in the mud, but others are piled up sitting on the lake bottom motionless or crawling along at a snail’s pace.  Common map turtles sit on the bottom or wedge themselves amongst rocks and logs.  When disturbed they retreat, and may reveal a northern leopard frog underneath, which will also swim away.  Hardly asleep, these map turtles require more oxygen than painted turtles buried in the sometimes anoxic mud.  The cold and relative inactivity allows them to take in all the oxygen they need from water.  Frogs and softshell turtles breathe through their skin, but softshells also take in oxygen through special adaptions in their throats.   
Oshkosh Ice Night
Frozen Lake Winnebago at Oshkosh

Mammals have no options but to breathe air.  The local aquatic members of the weasel family--river otter and mink--must maintain holes in the ice with their teeth to be able to gain access to the fish, frogs, turtles and other animals they eat.  Muskrats often use the same holes, but they try to stay concealed, and will never walk on ice and snow if they can avoid it.  Muskrats build huts, or lodges like beavers do, but muskrat homes are made of aquatic plant leaves, stems, and roots.  Here they sleep and eat, but they often swim far beyond the range of one breath to obtain the food they need.  For those foraging trips they build cave-like “push ups” for breathing.  They will also build small feeding huts, which are self-explanatory.  A sudden drop in water levels after the ice forms seals off all these structures from the muskrats’ food, forcing them onto ice and snow and into the jaws of coyotes.    

Winter is a harsh time for wildlife, but it can be easier under the ice and snow for those adapted to it.

Previously published in the Oshkosh Scene article.