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Messages - Phil42

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Science / Re: ICESAT-2
« on: October 05, 2018, 02:25:59 PM »
ICESat-2 Laser Fires for 1st Time, Measures Antarctic Height

"Next up for ICESat-2 is a suite of procedures to optimize the instrument, Neumann said, including tests to ensure the laser is pointing at the precisely correct angle and lasing at the precisely correct wavelength to allow as many photons as possible to hit the detector.

“It will take a couple of additional weeks,” he said, “but about one month after launch we’ll hopefully start getting back some excellent science-quality data.

Arctic sea ice / Re: 2018 sea ice area and extent data
« on: October 03, 2018, 04:18:07 PM »
Thanks for that, I'd also like to know the last date that was between 1,000 square kilometers gained and 1,000 square kilometers lost.

Intersting question, here is what I found:
  • It usually happens around 3-5 times a year (mostly but not exclusively around maximum or minimum).
  • The last time it happened was the 23. September 2017, a drop of 458km2.
  • The smallest daily change I found was a drop of 12km2 dated 15. September 1989.
  • It has never happened for more than 2 consecutive days.

Antarctica / Re: Rift in Larsen C
« on: September 28, 2018, 01:18:52 PM »
The iceberg and all the surrounding ice have drifted quite a distance southward in the last 2 days. I would estimate the distance ~5km.

Quote from: NASA ICE, 21.09.2018
Week 1 update: #ICESat2 is looking great!
Solar array deployed, all subsystems turned on, and we’re busy checking everything out. Navigation works perfectly, guiding us along our planned orbit.
 ~1 week until it's time to open the door & turn on the laser!

Everything is looking good for our new hope for better data collection up there. We will probably get another update after the first laser tests. I'm really excited for this one.

Arctic sea ice / Re: The 2018 melting season
« on: September 19, 2018, 02:23:51 PM »
As the freezing season thread has opened and the 2018 melting season comes (has come?) to an end, I'd like to throw a big THANK YOU at everyone who has contributed to this thread and the interesting discussions.

I am mostly a lurker on this forum but come here almost daily reading through the posts. This was the first melting season I followed like this and I have really learned a lot because of everyone here.

Looking forward to the freezing season now

Arctic sea ice / Re: 2018 sea ice area and extent data
« on: September 19, 2018, 11:11:43 AM »
September 17th: 4'491'419km2, a decrease of -22'092km2.

As Brigantine mentioned, this is the new 2018 minimum, ranking as 7th lowest after overtaking 2008's minimum (and 19'194km2 above 2017's minimum).

September 18th: 4'501'564km2, an increase of 10'145km2.

Extent is now below 2015 and back down to 5th place. I'm sure Juan and gerontocrat will provide more insight, I'm just filling the spot here with Brigantine because of the data delay.

Arctic sea ice / Re: The 2018 melting season
« on: September 11, 2018, 09:27:44 AM »
Looks like the southern part of the ESS arm and the "Beaufort Island" are slowly melting away after all. On the other hand I think a small extent increase towards the Amundsen Gulf is observable.

Arctic sea ice / Re: "Stupid" Questions :o
« on: September 08, 2018, 11:48:57 AM »
Thanks a lot for the informative answers!

Arctic sea ice / Re: 2018 sea ice area and extent data
« on: September 07, 2018, 10:25:40 PM »
2018 is the 11th year with a minimum below 5'000'000 km². Since 2007, every year with exception of 2009 had a minimum below 5'000'000 km².

Here are the dates when the other 10 years passed the 5 million mark again in the freezing season, ordered from earliest to latest.

2014 - 21. September
2013 - 22. September
2010 - 25. September
2016 - 27. September
2017 - 29. September
2008 & 2015 - 30. September
2011 - 2. October
2007 - 9. October
2012 - 14. October

Let's see which position 2018 will take in this statistic

Arctic sea ice / Re: "Stupid" Questions :o
« on: September 07, 2018, 10:02:33 PM »
Hi, I have two rather simple question I unfortunately don't know the answer to. Please also correct me if something I wrote is wrong, I love to learn new stuff.

1) During the melt season, as I understand it, there is top melt (from exposure to the sun and warm air temperature) and there is bottom melt from the water underneath the ice (this gets more significant with strong winds because the warm water which is usually further down gets mixed with the colder water above).

So to my question: Which of those factors is more prevalent / contributes more to melt?

2) During the freezing season, does it even matter if the air is -5°C or -20°C. It might sounds stupid, but in my understanding water freezes at ~0°C, so does the amount below 0 make a difference?
I ask this because of the very high winter temperature anomalies in the arctic where temperatures sometimes spike up a lot but still stay under 0°C by a significant amount.

3) During the freezing season, how does cloud cover affect the ice. In summer it protects the ice from exposure to the sun, does it also have an effect in winter when there is no sun (apart from precipitation)?

Arctic sea ice / Re: September Predictions Challenge
« on: July 30, 2018, 01:51:08 PM »
I'm taking a little bit of a different approach here to make my (August?) prediction. I looked at the JAXA minimum extent ranks the previous years placed in (see graph below) and from there took the average rank, which is 4.21 from 1990-2017.

For 2018 to be placed at exactly this average rank of 4.21, the JAXA minimum extent would have to be 4'344'239km2.

So my prediction is
4.0 - 4.5 JAXA
4.5 - 5.0 NSIDC

(I am aware that is a really bad method to make a prediction but I was just wondering what the outcome of the calculation would be and though I might as well share it  ;))

Arctic sea ice / Re: 2018 sea ice area and extent data
« on: July 23, 2018, 09:05:12 AM »
We had now 6 consecutive days with a drop of over 90'000 km2 and an average of 112'731 km2.

In just the last 4 days 2018 got 209'909 km2 (24.5%) closer to the record minimum (2011). The record minimum will only go down by ~190'000 km2 (average 63'300 km2 per day) in the next 3 days.

Arctic sea ice / Re: 2018 sea ice area and extent data
« on: April 18, 2018, 11:26:05 AM »
Since we hit the 13 million km2 extent mark now, I decided to look at the dates when the extent hit this mark in previous years. I ordered them by the date it hit the mark and added the decade averages.

ASI Extent first time below 13 million km2 by year (JAXA):
2018: April 17
2016: April 19
2017: April 21
2004: April 22
2007: April 24
2006, 2014, 2015: April 26
2010's Average: April 28
2000's Average: May 4
1990's Average: May 13
1980's Average: May 21

edit: Looks like gerontocrat was faster than me, I'll leave the post up anyway.

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