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Wipneus
Netherlands
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Martin: If I understand it well enough, the controversial bits with Zwally 2015 is 1) about the timescale of the observed volume increases in East Antarctic and 2) the different results of the Grace measurements. 2) is targeted in "Alba Martin-Español et al, Constraining the mass balance of East Antarctica, Geophysical Research Letters (2017). DOI: 10.1002/2017GL072937" See also https://phys.org/news/2017-05-growth-east-antarctic-ice-sheet.html Abstract: We investigate the mass balance of East Antarctica for the period 2003–2013 using a Bayesian statistical framework. We combine satellite altimetry, gravimetry, and GPS with prior assumptions characterizing the underlying geophysical processes. We run three experiments based on two different assumptions to study possible solutions to the mass balance. We solve for trends in surface mass balance, ice dynamics, and glacial isostatic adjustment. The first assumption assigns low probability to ice dynamic mass loss in regions of slow flow, giving a mean dynamic trend of 17 ± 10 Gt yr−1 and a total mass imbalance of 57 ± 20 Gt yr−1. The second assumption considers a long‐term dynamic thickening hypothesis and an a priori solution for surface mass balance from a regional climate model. The latter results in estimates 3 to 5 times larger for the ice dynamic trends but similar total mass imbalance. In both cases, gains in East Antarctica are smaller than losses in West Antarctica. 1) The time period of the volume increases has implications for the density,thus for the mass increases (Zwally 2015 argues a density close to solid ice, other researchers assume a much lower density closer to fresh snow). Schröder et al have a paper in The Cryosphere Discussion. Discussion started March 19 and is open until May 14, no comments yet. This paper user observations over a much longer time span (1979-2017) and find a significant acceleration of the East Atarctic ice sheet volume. That (IMHO) makes is much more likely that the volume increases are mostly from snow, thus of low density. Abstract: We developed an approach for a multi-mission satellite altimetry analysis over the Antarctic Ice Sheet which comprises Seasat, Geosat, ERS-1, ERS-2, Envisat, ICESat and CryoSat-2. In a first step we apply a consistent reprocessing of the radar alitmetry data which improves the measurement precision by up to 50 %. We then perform a joint repeat altimetry analysis of all missions. We estimate inter-mission offsets by approaches adapted to the temporal overlap or non-overlap and to the similarity or dissimilarity of involved altimetry techniques. Hence, we obtain monthly grids forming a combined surface elevation change time series. Owing to the early missions Seasat and Geosat, the time series span almost four decades from 07/1978 to 12/2017 over 25 % of the ice sheet area (coastal regions of East Antarctica and the Antarctic Peninsula). Since the launch of ERS-1 79 % of the ice sheet area is covered by observations. Over this area, we obtain a negative volume trend of −34 ± 5 km3 yr−1 for the more than 25-year period (04/1992–12/2017). These volume losses have significantly accelerated to a rate of −170 ± 11 km3 yr−1 for 2010–2017. Interannual variations significantly impact decadal volume rates which highlights the importance of the long-term time series. Our time series show a high coincidence with modeled cumulated precipitation anomalies and with satellite gravimetry. This supports the interpretation with respect to snowfall anomalies or dynamic thinning. Moreover, the correlation with cumulated precipitation anomalies back to the Seasat and Geosat periods highlights that the inter-mission offsets were successfully corrected and that the early missions add valuable information. Paper: Schröder, L., Horwath, M., Dietrich, R., and Helm, V.: Four decades of surface elevation change of the Antarctic Ice Sheet from multi-mission satellite altimetry, The Cryosphere Discuss., https://doi.org/10.5194/tc-2018-49, in review, 2018 Link: https://www.the-cryosphere-discuss.net/tc-2018-49/
Toggle Commented Apr 19, 2018 on PIOMAS April 2018 at Arctic Sea Ice
the weight of the snow pushes the ice under the water level This is actually the normal in the Antarctic (as the paper you linked to mentions), and not so often, perhaps rarely, in the North. If the PIOMAS does not account for that effect (of snow-ice formation under snow), then it may actually be Crysat that is more accurate. Assuming that Cryosat under such circumstances has any accuracy left. I have always suspected that the reason Cryosat never (AFAIK) showed any analysis for the Antarctic was just this fact.
Toggle Commented Mar 12, 2018 on PIOMAS March 2018 at Arctic Sea Ice
Note that even without any random variations, any trend will make the standard deviation differ from zero. For that reason alone, this is not a Normal distribution, so 8 sigma does not have to have the same probability as that. There is no doubt though that the anomaly falls in some category labeled "crazy". I have put the graphs together on a page with some brief description of the methods and the data sources: https://sites.google.com/site/arctischepinguin/home/global-sea-ice There are two global sea ice volume graphs on that page as well, derived from GIOMAS. The graphs suggest that the current low area/extent are following big drops in volume earlier this year. Which makes sense of course.
Sam, sorry about the confusion. The grey area is the +/- 2 sigma range. I have modified the legend to make that clear. There are more graphs for those that want to look at the issue. In particular : https://sites.google.com/site/arctischepinguin/home/sea-ice-extent-area/grf/nsidc_global_area_normanomaly.png normalised anomaly (= anomaly / stddev) show the number of sigma's. See this post and the following on the forum for the set of graphs: http://forum.arctic-sea-ice.net/index.php/topic,1457.msg94284.html#msg94284
Ah, I remembered. Between "pre" tags, the alignment is preserved. Area: Arctic Basin East Siberian Sea Laptev Sea -16.3 0.6 -7.4 Kara Sea Barents Sea Greenland Sea -22.4 -17.0 4.0 Baffin/Newfoundland Bay St. Lawrence Hudson Bay 11.6 -14.7 -41.1 Canadian Archipelago Beaufort Sea Chukchi Sea 3.3 2.2 3.4 Bering Sea Sea of Okhotsk Total Area -3.7 -58.7 -156.4
Toggle Commented Mar 16, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
Your calculations are very helpful, but for the 174K drop, could you please share from NSIDC where this drop is happening? The opportunity to quote the exact values per region has gone (overwritten by totday's update). Here are some numbers from from area, calculated the NSIDC way: Area: Arctic Basin East Siberian Sea Laptev Sea -16.3 0.6 -7.4 Kara Sea Barents Sea Greenland Sea -22.4 -17.0 4.0 Baffin/Newfoundland Bay St. Lawrence Hudson Bay 11.6 -14.7 -41.1 Canadian Archipelago Beaufort Sea Chukchi Sea 3.3 2.2 3.4 Bering Sea Sea of Okhotsk Total Area -3.7 -58.7 -156.4 (sorry, I forgot how to align such tables on the blog) Here the drop is "only" 156k, CT exaggerates the area at lower latitudes. So the drop is mostly caused by Okhotsk, Hudson and the Bering/Kara/CAB section. I have uploaded in the forum what I call the delta map. Bright red and blue is where concentration crosses the 15% cut-off. Blueish where concentration increases by 7% or more, pinkish where concentration drops more than 7%. This should serve as a nice illustration. More information on the calculation is mentioned in the post just above that image.
Toggle Commented Mar 16, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
The 174K drop then actually happened yesterday Tuesday, March 15th, but will then reported by CT on Thursday, March 17th, and CT will use the date of March 16th. for this drop. Almost. NSIDC reports concentration data of the day before. So yesterday that was 14th. NSIDC calculates extent and reports that as the 14th. CT does not report its Arctic area figures (based on this data) two days later (Thursday). The Southern Hemisphere area and Global area numbers follow one day after that (Friday).
Toggle Commented Mar 16, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) Tue 2016.1973 +8.8 12.859880 +93.0 2.358840 +101.7 15.218720 Wed 2016.2000 +25.6 12.885500 +37.8 2.396603 +63.4 15.282103 Thu 2016.2027 -174.9 12.710576 +81.5 2.478095 -93.4 15.188671 (All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.) Seems like a good start of the melting season, an almost-near double century drop.
Toggle Commented Mar 15, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) Mon 2016.1945 +10.9 12.851103 +43.4 2.265887 +54.3 15.116990 Tue 2016.1973 +8.8 12.859880 +93.0 2.358840 +101.7 15.218720 Wed 2016.2000 +26.1 12.885960 +37.8 2.396603 +63.8 15.282563 (All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.) Also on Wednesday a new max.
Toggle Commented Mar 14, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) Sun 2016.1918 -12.6 12.840884 +33.7 2.222478 +21.1 15.063362 Mon 2016.1945 +10.9 12.851816 +43.4 2.265887 +54.3 15.117703 Tue 2016.1973 +9.0 12.860785 +93.0 2.358840 +101.9 15.219625 (All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.) If correct, CT area will report a new maximum this Tuesday (and possibly on Monday, that is too close to tell).
Toggle Commented Mar 13, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) Wed 2016.1808 +8.0 12.731853 +50.7 2.010823 +58.8 14.742676 Thu 2016.1836 +23.8 12.755649 +62.0 2.072837 +85.8 14.828486 Fri 2016.1863 +20.2 12.775896 +64.5 2.137373 +84.8 14.913269 Sat 2016.1890 +77.8 12.853706 +51.4 2.188778 +129.2 15.042484 (All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.) If correct, CT arae will report a new maximum this Saturday.
Toggle Commented Mar 10, 2016 on Mad Max 2: The Arctic Warrior at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1699 -22.3 12.692058 -6.2 1.808553 -28.5 14.500611 2016.1726 +54.7 12.746719 +48.1 1.856618 +102.7 14.603337 2016.1753 -21.3 12.725438 +37.0 1.893617 +15.7 14.619055 2016.1781 -2.0 12.723470 +66.5 1.960082 +64.5 14.683552 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. The freezing in the SH now well on its way, NH may linger a bit longer around its max, so the global minimum is not likely to change anymore anymore. These CT predictions will go into hibernation for now.
my CT-like calculation results for today (NH, SH, global) 2016.1671 -52.3 12.714314 +11.9 1.814750 -40.4 14.529064 2016.1699 -22.3 12.692058 -6.2 1.808553 -28.5 14.500611 2016.1726 +54.7 12.746719 +48.1 1.856618 +102.7 14.603337 2016.1753 -21.1 12.725594 +37.0 1.893617 +15.9 14.619211 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
my CT-like calculation results for today (NH, SH, global) 2016.1671 +15.6 12.766578 +9.0 1.802850 +24.6 14.569428 2016.1699 -52.3 12.714314 +11.9 1.814750 -40.4 14.529064 2016.1726 -22.3 12.692058 -6.2 1.808553 -28.5 14.500611 2016.1753 +54.2 12.746250 +48.1 1.856618 +102.3 14.602868 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. The first column is wrong (not like CT), starting at 1st of March, which CT has given the same "date" as 29th of February (making it quite useless). I'll fix that one of these days.
my CT-like calculation results for today (NH, SH, global) 2016.1644 +9.7 12.750962 -5.7 1.793830 +4.0 14.544792 2016.1671 +15.6 12.766578 +9.0 1.802850 +24.6 14.569428 2016.1699 -52.3 12.714314 +11.9 1.814750 -40.4 14.529064 2016.1726 -22.5 12.691812 -6.2 1.808553 -28.7 14.500365 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. The first column is wrong (not like CT), starting at 1st of March, which CT has given the same "date" as 29th of February (making it quite useless). I'll fix that one of these days.
my CT-like calculation results for today (NH, SH, global) 2016.1616 -35.4 12.741300 +9.6 1.799485 -25.9 14.540785 2016.1644 +9.7 12.750962 -5.7 1.793830 +4.0 14.544792 2016.1671 +15.6 12.766578 +9.0 1.802850 +24.6 14.569428 2016.1699 -52.2 12.714382 +11.9 1.814750 -40.3 14.529132 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. I may also be wrong in the first column when CT reports the results for 29 Feb and later. I'll fix it some time if needed.
my CT-like calculation results for today (NH, SH, global) 2016.1589 -67.6 12.776749 -9.8 1.789907 -77.4 14.566656 2016.1616 -35.4 12.741300 +9.6 1.799485 -25.9 14.540785 2016.1644 +9.7 12.750962 -5.7 1.793830 +4.0 14.544792 2016.1671 +15.4 12.766372 +9.0 1.802850 +24.4 14.569222 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. I can also be wrong in the first column when CT reports the results for 29 Feb and later. I'll fix it some time if needed.
my CT-like calculation results for today (NH, SH, global) 2016.1562 +89.5 12.844304 +6.9 1.799745 +96.5 14.644049 2016.1589 -67.6 12.776749 -9.8 1.789907 -77.4 14.566656 2016.1616 -35.4 12.741300 +9.6 1.799485 -25.9 14.540785 2016.1644 +9.7 12.750993 -5.7 1.793830 +4.0 14.544823 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today. I can also be wrong in the first column when CT reports the results for 29 Feb and later. I'll fix it some time if needed.
Toggle Commented Feb 29, 2016 on Global sea ice area record minimum at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1534 +135.7 12.754770 -14.3 1.792812 +121.5 14.547582 2016.1562 +89.5 12.844304 +6.9 1.799745 +96.5 14.644049 2016.1589 -67.6 12.776749 -9.8 1.789907 -77.4 14.566656 2016.1616 -35.6 12.741170 +9.6 1.799485 -26.0 14.540655 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
Toggle Commented Feb 28, 2016 on Global sea ice area record minimum at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1507 +138.5 12.619037 +37.2 1.807087 +175.7 14.426124 2016.1534 +135.7 12.754770 -14.3 1.792812 +121.5 14.547582 2016.1562 +89.4 12.844204 +6.9 1.799745 +96.4 14.643949 2016.1589 -66.2 12.777960 -6.1 1.793637 -72.4 14.571597 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
Toggle Commented Feb 27, 2016 on Global sea ice area record minimum at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1479 +33.4 12.480547 -4.7 1.769923 +28.8 14.250470 2016.1507 +138.5 12.619037 +37.2 1.807087 +175.7 14.426124 2016.1534 +135.7 12.754770 -14.3 1.792812 +121.5 14.547582 2016.1562 +89.7 12.844477 +6.9 1.799745 +96.6 14.644222 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
Toggle Commented Feb 26, 2016 on Global sea ice area record minimum at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1452 -113.6 12.447126 -33.0 1.774587 -146.5 14.221713 2016.1479 +33.4 12.480547 -4.7 1.769923 +28.8 14.250470 2016.1507 +138.5 12.619037 +37.2 1.807087 +175.7 14.426124 2016.1534 +135.3 12.754380 -14.3 1.792812 +121.1 14.547192 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
Toggle Commented Feb 25, 2016 on Global sea ice area record minimum at Arctic Sea Ice
Wipneus, Apparently half of the current sea level rise is natural. You have already lost me there, and it does not get better further. I am always happy to explain and discuss what I wrote, but here I have no idea what you mean.
Toggle Commented Feb 25, 2016 on Global sea ice area record minimum at Arctic Sea Ice
In rare cases the NSIDC updates its daily sea ice concentration data more than once per day. It just happened, and my recalculated data for once differ more than a few k :( . Only the last line that is, here are the updated numbers: 2016.1425 -42.9 12.560691 +15.3 1.807565 -27.6 14.368256 2016.1452 -113.6 12.447126 -33.0 1.774587 -146.5 14.221713 2016.1479 +33.4 12.480547 -4.7 1.769923 +28.8 14.250470 2016.1507 +138.5 12.619010 +37.2 1.807087 +175.6 14.426097
Toggle Commented Feb 25, 2016 on Global sea ice area record minimum at Arctic Sea Ice
my CT-like calculation results for today (NH, SH, global) 2016.1425 -42.9 12.560691 +15.3 1.807565 -27.6 14.368256 2016.1452 -113.6 12.447126 -33.0 1.774587 -146.5 14.221713 2016.1479 +33.3 12.480444 -4.7 1.769923 +28.7 14.250367 2016.1507 +68.6 12.549091 +42.4 1.812297 +111.0 14.361388 All calculated from today's NSIDC sea ice concentration data and only occasionally differ more than a few k from the final values released by Cryosphere Today.
Toggle Commented Feb 24, 2016 on Global sea ice area record minimum at Arctic Sea Ice