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Topics - Whit

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Developers Corner / Rapid Response vs. Worldview
« on: June 08, 2013, 08:51:17 PM »

Is there any difference in image-quality?

I see most people here use the RR images, and I can understand why if you want large files that caver a lot of area. However, I find the Worldview-interface so much better. If all you need is a cropped image from 100% zoom, is there any point in not using Worldview?

Inquiring noobs want to know :)

2
The rest / The Iceman
« on: May 03, 2013, 10:12:07 AM »
His bearded head showed up near that near-permanent area of open water in The Chuckchi Sea. This is from May 1st. The ice almost seems to fall into the hole in that area, so I don't think he will stay around for too long.

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Arctic sea ice / Mechanical tipping points - are we seeing one now?
« on: April 16, 2013, 06:53:05 PM »


First time poster here. I decided to jump straight in.

I've been following the blog since last season, while becoming a more and more avid ice-watcher since I started noticing the changes around 10-15 years ago. I'm a complete amateur when it comes to the science of ice, oceans and hydrology.

I hang around in the sub-arctic quite a lot, and the changes in wildlife, vegetation, natural cycles of insects, spring run-off etc has changed tremendously in the areas i frequent. I was born and grew up between 69N and 78N. That background has given me the opportunity to experience a lot of ice-offs, both in fresh and salt water.

Looking at the satellite images and the cracking I'm reminded of what it's usually like when you wait for ice-off on an alpine lake north of the polar circle.

When the ice cracks and takes on a more porous character one early morning, it's usually completely gone the next day. Ice-fishermen have been forced to swim to shore after pitching their tent on what they thought was solid ice.

I believe it has as much to do with mechanics as with how much thermal energy is available to melt ice. What happens IMHO, at least in fresh water, is that as the ice cracks, the surface that water or air can transfer heat to increases exponentially. It's not just the cracks per se. It's also the way the ice turns porous at the onset of melt. This porosity again increases the effective surface of the ice by several orders of magnitude. The porosity also translates to lower albedo.

My gut feeling is that the mechanical and thermodynamic interaction of ice and water, and the way the quality and character of ice changes when at the onset of melt, is underestimated in the models. In particular the extreme increase in effective surface area when the ice first cracks up and then as porosity increases. In addition there is increased surface area for kinetic energy to work, higher drift speed translating to even higher kinetic energy, less resistance towards mechanical forces like wind and waves and so on.

If I'm right 2014 or 2015 at the most seems like a good bet for ice-off considering the current state of the ice, and considering the current trend. Please take into account that ice-off is not the same as ice-free. Ice-off is the last phase before an ice-free state, at least in my vocabulary :)

This isn't based on much besides personal experience with ice, and I realize the limitations of using freshwater high alpine lakes in the arctic as models of sea-ice. Any input would be much appreciated. I have already learned a lot from the ASIB and ASIG, and now is as good time as any to join the eminent ASIF :)

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