Vasily Smolyanitsky Arctic and Antarctic Research Institute St.Petersburg, Russian Federation

1. Development of the Arctic Ocean statistical parameters describing variability of ice conditions for the 20th century Vasily Smolyanitsky Arctic and Antarctic Research Institute St.Petersburg, Russian Federation JCOMM Expert Team on Sea Ice (ETSI)

2. Summary of ice charts data collections within the WMO Global Digital Sea Ice Data Bank Project • Basic statistics describing “mean” sea ice state for the second part of the 20th century • Extended statistics, including PDFs approximation, describing special features of ice conditions • Analysis of temporal variability based on ice index data and revealed periods of sea ice variability

3. Summary of GDSIDB content The main five GDSIDB datasets are described in the table. Included are also the period, covered by dataset, existence of gaps, sea ice parameters in dataset and number of charts in SIGRID format (WMO, 1989). Total number is > 10000. Samples are on next slide… CT– total concentration, SD – stage of development and partial concentration, SV – ice thickness, FI – fast ice information.

4. Samples of ice charts from national ice services, historic & modern 1. AARI, Russia 4. FIMR, Finland (for BSIM) 5. JMA, Japan 2. NIC, USA 3. CIS, Canada

5. Arctic total concentration blended data set for 1950-1998 based on GDSIDB ice charts • First version was completed in December 2002 (thanks to Hadley Center support) • Blending was done on a 15’x15’ grid (45-90N) with monthly interval averaging • Additional monthly Northern Hemisphere 1 degree ice extent dataset (J.Walsh dataset) included • Gaps were populated by climatic monthly median values • Result contains :-) 26% (GDSIDB), 25% (JW), 49% (Climate) :-( • Output is user-friendly and includes 2 files: factual data and flags of origin for each cell • In 2005 extension of blended dataset was done by inserting values (based on AARI data) for Eurasian Arctic for 1933-1949 period

6. Spatial statistical analysis (1950-1998):1) sea ice mean state (blended dataset) April (median) Winter (robust) mean Summer (robust) mean August (median)

7. 2) special features of ice conditions - extended set of statistics assessed on individual datasets: Statistics for total concentration in summer period (AARI data)

8. 3) …skew, curtosis and PDFs (app.by Pirson curves): Skew (r3), curtosis (r4), winter Skew (r3) and curtosis (r4), summer PDF type = f(r3,r4) PDF app., winter PDF app., summer AARI and NIC total concentration data

9. 3add) …PDFs based on SSMR-SSMI data (app.by Pirson curves), useful for near NP region: J-type PDF app., February PDFs app., May PDFs app., August Data: SSMR-SSM/I Bootstrap total concentration daily patterns for 1978-2002

10. 2 2 km km *1000 *1000 1600 1200 2000 y = -1.2603x + 989.27 1400 1800 y = - 5.1265 x + 1270.4 1000 1200 1600 1000 1400 800 800 1200 y = -2.5993x + 600.03 600 1000 600 y = - 1.2033 x + 1092 400 800 200 600 400 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 y = -0.9572x + 299.6 400 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 200 y = -2.5367x + 183.06 0 1968 1973 1978 1983 1988 1993 1998 2003 Temporal analysis of ice index data:Variability and linear trends in August for Eurasian (1900-2003) and Canadian Arctic (1968-2004) Greenland, Barents, Kara Laptevs, Eastern-Siberian, Chukcha Western CA (blue) Eastern CA (green) East Coast (red) (April) Hudson Bay (light blue)

11. a № Area Month Mean Min Max 95% 95% Period of observations 1900 – 2003 гг. 1 Greenland VIII - 0.954 - 1.463 - 0.446 2 Barents VIII - 2.638 - 3.324 - 1.952 3 Kara VIII - 1.533 - 2.488 - 0.578 4 Greenland – Barents – Kara - 2.863 - 4.389 - 1.337 5 Laptevs VIII - 0.381 - 1.023 +0.261 6 Eastern - Siberian VIII - 0.368 - 1.068 +0.332 7 Chukcha VIII - 0.453 - 0.743 - 0.163 8 Laptevs – Eastern - Siberian – Chukcha - 1.202 - 2.488 +0.084 9 Eurasian Arctic VIII - 2.737 - 4.381 - 1.093 Period of observations 19 68 – 200 4 гг. 1 0 Eastern Canadian Arctic VIII - 2.599 - 6.377 +1.179 11 Western Canadian Arctic VIII - 1.260 - 4.053 +1.532 12 Hudson Bay VIII - 2.537 - 5.240 +0.166 13 Ca nadian Arctic VIII - 7.079 - 13.580 - 0.578 Validity of linear trend coefficients by regions (95%)

12. Wavelet analysis of sea ice extent variations for Eurasian Arctic Seas (based on 1900-2003 period) and Canadian Arctic Seas (based on 1968-2004 period) in August (red – more ice, blue – less ice) Greenland Barents Kara Laptev Eastern-Siberian Chukcha Western CA Eastern CA Hudson Bay

13. Conclusions • Ice charts collections and blended datasets within the GDSIDB project provide possibility to assess various climatic statistics including sea ice “mean state” for the second part of the 20th century • Different statistics may and should be chosen for climatic analysis and to underline special features of ice conditions, robust and PDFs are preferable • Abnormal types of PDF like U, I, J-form are predominant for sea ice total and partial concentrations in seasonal cycle, approximations of PDFs may be used for classification schemes or in modelling • Linear trend analysis based on ice charts and index data gives a typical picture of a negative trend from 1900s to ~2000, however transition to sub-periods or regions gives a much more complex picture with coefficients varying in magnitude and sign • There is a strong indication that the sea ice variability in at least Eurasian and Canadian Arctic has a polycyclic structure with noticeable periods of approximately 10, 20 and 60 years and periods of longer duration revealed as linear trend