This is Dominik Lenné's Typepad Profile.
Join Typepad and start following Dominik Lenné's activity
Join Now!
Already a member? Sign In
Dominik Lenné
Recent Activity
Quite OT so I keep it short: one thing to do is support of the implementation and/or development of schemes to put a price to emission of GHG like an emission certificate system. Simply logical.
@Bruce Worden about snow cover: Thank You very much for the link but I find the trend in those plots not convincingly increasing - and its not snow thickness on the ice sheet but snow area on land, which depends on different causes and has different effects. I did a short unsuccessful web search on snow thickness on the ice - may be somebody has it in his/her bookmark list.
about Aarons post: The humidity - snow cover - mechanism is compelling. Now arises the question: are there observations of increasing snow cover thickness in winter?
So, any interested person may get a working freemat script for creating effective thickness maps out of thickness and concentration maps from the godiva model ( from here: some example files are there too. HTH
Toggle Commented Aug 16, 2012 on New site with new thickness maps at Arctic Sea Ice
This (using Photoschop to generate an "effective thickness map") was more a proof of concept. BTW does the job as well if not better. To do this with a complete set of images or regularly would IMO require some scripting to yield reproducible results - and save worktime. This can be achieved with Freemath - I'm working on it. Have just discovered this marvelous program and have not fully explored its possibilities. The same map, this time made with Freemath: I am going to make the script publicly available too, when it is a bit more mature.
Toggle Commented Aug 13, 2012 on New site with new thickness maps at Arctic Sea Ice
I managed to produce an "effective thickness" map from the godiva ( thickness and area fraction maps with guess what? Photoshop. Download the maps as greyscale, open one in PS, create a multipication level and paste the second one in it. Then create a modification level and fiddle around with the gradation curves to get the color coding. To be seen here: It looks plausible but I didn't check it meticulously.
Toggle Commented Aug 11, 2012 on New site with new thickness maps at Arctic Sea Ice
It would really be interesting how exactly they come to their thickness data. IMO something like an "ice area mass density" - map would be interesting, too. AFAIK this is thickness * concentration * volume mass density. The latter will be very hard to obtain and could for the time beeing assumed constant.
Toggle Commented Aug 11, 2012 on New site with new thickness maps at Arctic Sea Ice
@Aaron Lewis: You wrote to have seen already 2002 that something was "out of control". Could you give some links or clarifications concerning the statistics and methods by which you/your group achieved that? I find that very interesting (maybe others too).
Don't hit me if I write mere trivialities. If I eyeball sharply the plot on, wich Neven gave, I can see not only stronger anomaly values and bigger variability, but also a clear seasonal pattern of the anomaly beginning with about 2007. This is interesting as the anomaly is a construction especially made to be freed from seasonal changes. This (metastable???) change in seasonal anomaly pattern is also clearly visible in the PIOMAS volume anomaly plot as 3 downpointing spikes in late spring. The area anomaly pattern change is surely in part due to the bigger oscillation amplitude of sea ice area, which in turn is equivalent to the shrinking of multiyear ice area. With volume anomaly pattern it's a little bit different, as it points to an earlier onset of melting and a much stronger "melting dynamics" in spring / early summer compared to pre-2007 years. All this might not only be a byproduct of just thinner ice but also indicate an additional change in the yearly energy flow pattern with more energy coming in during summer by radiation / air / water currents - and/or higher loss by ice blown away. I cannot judge that. Striking is, that the onset of the yearly anomaly pattern is so clearly located in 2007. It looks as if with one at its time exceptional event (the 2007 melting) something basic has changed. I am scratching my head to find out what this points to.
Thanks for that one. A goog chuckle keeps the doctor away.
First thank You Peter for Your clarifications on CryoSat and the links to the beautyful images with the web of satellite tracks - and to Neven concerning the data sources. Concerning ice-freeness, I see two approximative parameters: the steady state summer ice area for a given mean arctic temperature/radiation situation, and the time constant of the adaption to the new regional climate. Latter can be estimated from the much discussed "no tipping point" - study ( in the order of magnitude around 2 years for the tinner ice - may be a little bit more for the thicker. As one can see here (, even 3m of ice can easily be molten down in one summer. Concerning the former: when we'll reach near ice-freeness depends, I think, much more on how regional climate will develop than on how much ice volume is there actually. I believe (believing is not knowing) that even in case PIOMAS underestimates ice mass, this does not make a big difference, if regional temperature rises continue. Summer ice will remain in those places where the mean temperature is low enough. The "citadel of frost" is the decisive point of the summer ice battle.
Concerning PIOMAS and its verification - it's now one and a half year that CryoSat 2 is spitting out terabytes of data and still no ice thickness map published except one in June 11. This is one thing I'm wondering about very much. (I think I did it some time ago on this blog, did I?) (rant)What is this satellite good for, I mean it's meant to produce thickness maps, isn't it? Instead they showed off sea level anomaly maps where you can see every bloody eddy of the gulf stream. (Probably grossly unjust.)(/rant) Other question: does anybody here know of arctic air temperature maps, monthly mean over 10 yrs or so, just to satisfy some weird interest of mine.
Looking at the last five years (07, 08,09,10 and 11 that is), it appears that volume anomaly has a downward flank that starts somewhere in the spring and ends in late summer. If this is not purely statistical, it would mean, that volume anomaly drop in those last years is not so much driven by slower freezing, but by faster melting. This could pretty much be the onset of one or more feedback processes. In a simple model, melting rate is more or less linearly dependent on air temperature, plus irradiation of course, but not much on ice thickness, because the heat flow is used up in the melting layer. Any feedback, in which the thinness contributes to accelerating volume drop, would go over the area: thin ice opens up faster at the edges, leaves ocean water to be both warmed and pushed by the wind to melt from the bottom. Also, wind might cause turbulence and desturb the thermo-/halocline. The heat in deeper waters would be more than enough to melt all the ice.
Very fine information. Even with validity limited to less than .5m, there is now one gauge more to calibrate PIOMAS and other models and narrow error bars. I too was wondering why there is (at least to my knowledge) virtually no thickness data coming out of the CryoSat project.
I wonder for quite a while why everybody seems to focus on sea ice extent. For the amount of energy necessary to melt the ice, volume is of course the dimension of choice (granted, that there are big insecurity margins) and for the albedo change, area is much more significant. So how come? I would really suggest a focus shift!
For comparison of the old, graph extracted and new, upgraded piomas data based plot look here:
Toggle Commented Jul 4, 2011 on PIOMAS Version 2 at Arctic Sea Ice
Dominik Lenné is now following The Typepad Team
Apr 9, 2010