Ice Melt Theory


If you’re anything like me, a couple nice days like we just had and I’m all in for summer.  Snow is gone, the sun feels lovely and warm, and the grass is trying to turn green so my brain is heading to one spot only. My brain is saying: Do not pass go, do not collect $200- head straight to summer and skip everything else.  I’m ready to break out the flip flops, patio furniture, lazy afternoons on the boat and grilling every single night. Except, there is one nagging thing that the sun and warm temps don’t seem to be taking care of quick enough- the ice on the lake.


A big part of our summer hinges on that lake melting.  And I, foolishly, was expecting the ice to melt as quickly as the snow.  My dreams were shot down yesterday, in our 70 degree day, when I saw ice fishermen still on the lake.  Yep- it was 4/22 and 70 degrees out and I saw like three fishermen setting up camp on the ice. Now, these could be exceptionally foolish fishermen about to receive their Darwin Awards and they probably have no place being on the ice this late anyway, but they survived without breaking through and that really crushed my summer lovin' dreams.


Just as I was trying to figure out how deep the ice on the lake could be- a post on the Lake Minnetonka Fan Page on Facebook popped up and showed twenty-two inches of clear ice and two inches of cloudy ice on West Arm.   Argh! So- I needed to arm myself with facts and figures to calm the feeling that we will never make it out of this winter and figure out how fast that stuff can melt and when can I hear the sounds of boats going by and not ice fishermen walking to their honey holes.  


The sun and warm temps took care of 15 inches of snow pretty darn quick, but ice doesn’t seem to melt the same way snow does.  I did my best Einstein impression yesterday and set out to answer that questions everyone is asking- when will ice out be?


However, I didn’t find any clear equation or algorithm for ice melt. Einstein's theory on mass energy equivalence (e=mc^2) did seem fitting for a title since I'm trying to figure out when the sun's energy can melt this mass of ice, but I'm using a little too many hypothetical and unmeasurable variables to get a straight answer from it. So I tried subbing in some figures in the Pythagorean theorem or Euler’s equation and get the exact date that Lake Minnetonka will fully be open but sadly that didn’t work either. So- I consulted my good friend Google and asked- how quickly can ice melt.

There are different stages in the ice melting process.  The Minnesota Department of Natural Resources explains it nice and succinctly here.  Basically, there are two ways the ice melts.  One- the water warms up from the sunlight penetrating through the ice layer (kind of like a greenhouse effect) and the liquid water starts warming below the ice layer.  As the water gets warmer and warmer- it starts eroding the ice from below the surface. This actually starts happening after the initial complete freeze over because once the ice has formed, the water is insulated from the temperatures above and the captured heat from the summer inside of the ground at the bottom of lakes start to slowly warm up the water.  Two- the warming temperature and external forces such as wind, rain, and puddles forming help erode the surface of the lake and help melting occur up top.

We start to hit critical mass melt when the ice thins to between four and twelve inches.  The sun penetrating through the ice makes these little “channels” called candles and helps the sun’s energy conduct even more efficiently into the water to speed up this melting process.  The ice starts to look dark because it is no longer reflecting as much sunlight. As a result of less reflection, the lake absorbs more energy and the water below the ice continues to warm up.  Little puddles of melted ice form these “candles” and help start to break apart the ice sheet. And finally- the wind comes along and starts blowing the ice sheets apart and piles them onto shore.  Did you know that as the ice moves to shore, it makes a tinkling sound as it bumps up against each other? Not only is ice melting beautiful, it sounds nice too!

Pictured below is a close up of the candling of the ice on Lake Minnetonka. You can see how this has moved far enough into the candling stage that water can now penetrate through the ice and drain into the water below. Even if the thickness of this ice is around 4-6 inches, it is not safe.


Eventually we get to a nice wide open lake and summer fun has begun!  But, I still didn’t answer when Lake Minnetonka is going to be open. We know that Minnesota is far behind in the ice out game this year.  Lake Pepin was the first lake declared ice out in Minnesota, like two days ago, which is about three weeks later than usual.


It looks like most of the channels have turned into the candle stage of ice melt and those should be breaking up and opening soon.  Underneath Coffee Bridge, near Lord Fletcher’s, is open and underneath the bridge on North Shore Drive over the channel into Forest Lake Bay is open. Grays Bay Dam has been opened to help assist in the ice melt.  This helps because any time there is significant movement in the water below, it can help break up the ice shelf even faster.

Pictured below is the candling of the ice in the channel into Forest Lake Bay and the beautiful sight of open water underneath the North Shore Drive bridge. This picture was taken yesterday so I have to believe that we have made even further progress in the ice melting game.


A rough rule of thumb is for a calm sunny 50 degree day, you can expect about two inches of ice loss.  The sun helps decay the ice by causing the candling of it so the water below is warming up even if the top isn’t open yet.  If our temperatures stay above freezing overnight, which they are forecasted to, and we continue to stay in the high 50’s and beyond, then I am guessing an ice out of May 2nd.  It is not the worst it has ever been, but its not the best. There is light at the end of this winter tunnel and we shall see if my Ice Melt theory is accurate this year!