Arctic Sea Ice Reality

more recent data here:
https://climategrog.wordpress.com/cpom_arctic_ice_vol_mths_2019-2/

Since 2011 Centre for Polar Observation and Monitoring ( CPOM ) have been using Cryosat2 data to estimate sea ice thickness and volume. Since the remote sensing instruments are unable to differentiate between pools of water on top of ice and open water, results are not published for the summer months. The annual minimum occurs during the middle of September. The closest indication of this in the CPOM data is the sea ice volume average for the months of October.

CPOM provide detailed graphs and maps for both poles as well as the following graph of monthly averages.

http://www.cpom.ucl.ac.uk/csopr/seaice.html?show_cell_thk_ts_large=1&ts_area_or_point=all&basin_selected=0&show_basin_thickness=0&thk_period=0&select_thk_vol=select_vol&year=2017&season=Spring

This graph just looks like a rectangular grid of dots with a couple of outliers; a general downward trend and slight up-tick in 2017. The problem is, there was a notable increase in volume from 2012 to 2013 which is close in magnitude to the change from month to month during refreezing. So, without clear labelling, the eye tends to associate the first three data points for the months of November with the following years’ dots from October. The natural inclination to ‘join the dots’, which we all learn to do as children. This creates a steady downward trend by inadvertently mixing different months. Replotting the same data, linking the progression of each month of the year, shows more clearly how ice volume for each season has evolved. The marked increase in volume during the winter of 2012/13, through all recorded months, becomes clearly apparent. The downward drift in minimum, becomes a upward drift.

It is quite surprising to realise that these two graphs contain exactly the same data points.

In particular, the dramatic 65% recovery in annual minimum from 2012-2013 ( the most significant change in the record ) is not at all apparent in the CPOM presentation. After all the media coverage of the 2012 minimum and claims of imminent “ice free Arctic” conditions, this equally dramatic “good news”, just a year later, went totally unreported in the media.

2012 10 15 5.4705
2013 10 15 9.0416
(9.0416-5.4705)/5.4705 = 65%

Data source : Centre for Polar Observation and Monitoring.
http://www.cpom.ucl.ac.uk/csopr/data.html

ref.
Laxon S. W., K. A. Giles, A. L. Ridout, D. J. Wingham, R. Willatt, R. Cullen, R. Kwok, A. Schweiger, J. Zhang, C. Haas, S. Hendricks, R. Krishfield, N. Kurtz, S. Farrell and M. Davidson (2013), CryoSat-2 estimates of Arctic sea ice thickness and volume, Geophysical Research Letters, 40, doi:10.1002/grl.50193.

Monthly data values kindly provided in personal communication by Andy Ridout. ( Uncertainty estimation t be communicated. )

2011 1 15 18.9930
2012 1 15 18.9187
2013 1 15 18.0477
2014 1 15 21.1604
2015 1 15 20.5743
2016 1 15 18.7123
2017 1 15 18.6750
2018 1 15 18.8078

2011 2 15 22.8615
2012 2 15 21.9790
2013 2 15 20.8219
2014 2 15 24.0771
2015 2 15 23.8487
2016 2 15 22.7818
2017 2 15 21.8671
2018 2 15 21.7819

2011 3 15 25.5193
2012 3 15 25.2995
2013 3 15 24.5354
2014 3 15 26.8294
2015 3 15 25.9263
2016 3 15 24.5047
2017 3 15 24.1490
2018 3 15 24.1602

2011 4 15 25.5528
2012 4 15 25.0312
2013 4 15 24.1399
2014 4 15 26.4783
2015 4 15 27.1147
2016 4 15 24.1579
2017 4 15 23.8746
2018 4 15 23.9700

2011 10 15 5.3185
2012 10 15 5.4705
2013 10 15 9.0416
2014 10 15 7.6322
2015 10 15 6.8420
2016 10 15 6.2846
2017 10 15 7.4316

2010 11 15 11.4922
2011 11 15 10.3784
2012 11 15 10.1826
2013 11 15 13.2027
2014 11 15 12.8336
2015 11 15 11.9310
2016 11 15 10.4033
2017 11 15 11.9012

2010 12 15 14.7203
2011 12 15 14.1706
2012 12 15 14.2510
2013 12 15 17.3288
2014 12 15 16.8339
2015 12 15 15.8137
2016 12 15 15.0048
2017 12 15 15.5735

Gnuplot script to produce graphic.

datafile="CPOM-arctic-vol_months.dat"

set xdata time
set timefmt "%Y %m %d"
set xtics format "%Y"

set title "CPOM Monthly Arctic Sea Ice Volume"
set xlab "http://www.cpom.ucl.ac.uk/csopr/data.html"
set ylab "ice volume / 10^6 sqr km "


set key top left Left rev

plot datafile using 1:(($2==10)?$4:NaN) with linespoint  title "oct" \
, "" u 1:(($2==11)?$4:NaN)  w linesp  tit "nov" \
, "" u 1:(($2==12)?$4:NaN)  w linesp  tit "dec" \
, "" u 1:(($2==1 )?$4:NaN)  w linesp  tit "jan" \
, "" u 1:(($2==2 )?$4:NaN)  w linesp  tit "feb" \
, "" u 1:(($2==3 )?$4:NaN)  w linesp tit "mar" \
, "" u 1:(($2==4 )?$4:NaN)  w linesp  tit "apr" 

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