Oceanographic and glacier information from
observations of 330 000 Antarctic icebergs
Olav Orheim, NPI & GRID-Arendal*
Norsk Geofysisk Forening, Solstrand
21 October 2015
* With collaborators Barry Giles & Jo Jacka, Australian
Antarctic Division, Hobart, and Are Bjørdal, Stein Tronstad
& Jan-Gunnar Winther, Norwegian Polar Institute, Tromsø
The Antarctic ice masses flow outwards to form floating ice shelves
which give rise to the large tabular icebergs, or grounded glaciers which
forms smaller icebergs. The tabular bergs may reach 100 x 50 km².
Annual Antarctic iceberg production is around 2000 km³. At any time
there are more than 200 000 icebergs floating in the Southern Ocean
1977: HRH Prince Mohamed Al-Faisal Al-Saud established Iceberg
Transport International & Icebergs For the Future (IFF).
IFF contact Olav Orheim about getting field iceberg data. OO involves
Arne Foldvik, UnivB – they study icebergs on NARE 1978/79.
1981: OO establishes, through SCAR, International Iceberg Observing
Programme, the so-called «Blue forms».
Since then 223 ship cruises have made 28 100 observations of altogether
338 800 Antarctic bergs, of which 271 500 have been classified by size. The t
Blue forms were sent to all
institutions with research
vessels going to Antarctica.
The instruction was to
record icebergs every six
hours, classified into five
size classses. An observation
is typically of what is seen
within a 12 nm (22 km)
radius, i.e. within 500 km².
% size distribution of 271 599 bergs:
Observed size classes (m)
10-50 50-200 200-500 500-1000 >1000
39,2% 33,1% 18%
7,3%
2,5%
Geographic distribution
of the observations:
Density of observations
mirror ship tracks to the
coastal research stations. The
number of observations are
particularly large around the
northern part of the Antarctic
Peninsula, which has the
highest density of stations.
Number of observations are
given for each «box» of 1°
latitude x 5°longitude. A box
is white when there are no
observations.
Total area of observations is approx. 14x10⁶km
Concentration of
icebergs
(defined as total no. of bergs
in box/no. observations).
Distribution reflect
both variations in
sources, and the
currents around
Antarctica.
Note “exit” routes
for the bergs.
The currents around
Antarctica
Yellow line marks Antarctic
Convergence
Dashed line is the Antarctic
Divergence. This divides the
clockwise and anticlockwise
currents near the continent
Zero iceberg
observations.
i.e. observations of no
icebergs in a box. At
60°S the area of a box
of 1x5° is 30 000 km²
(9000 nm²).
Frequency of zero
iceberg observations
(zero berg observed
/no. obs.).
Obviously the frequency
will increase with
distance from the
continent, but there
are also other patterns:
* high at the Divergence
* high in the Ross Sea
High frequency of zero
berg observations
north of Dronning
Maud Land coincide
with the Antarctic
Divergence which
divides east and
westward trending
currents (dashed line).
The bathymetry of
the Southern Ocean
is one factor in the
distribution of the
currents.
The deep ocean
exchange with the
underside of the ice
shelves is another.
Satellite
interferometry
shows the regions
of major mass loss
from the
Perimiter of
Antarctica.
Number of
icebergs > 1000m
Concentration of bergs
>1000m
(Number bergs > 1000m/
number of observations in
each box)
Some observations, which still needs statistical testing
Large year-to year variations – reflecting variations in calving rates? i.e:
1986/87: 17 bergs /observation (1400)
All other years 1982-89 around 12 bergs/obs, most years 1500 + obs.
Minimum in 1992/93 with 7 bergs/obs (1600)
Very large regional variations:
Sector out from Pine Island Bay largest density: > 17 bergs/obs.
Out of Ross Sea has lowest density, < 7/obs, but largest proportion of
largest icebergs size, with 5% > 1000m.
Smaller seasonal variations than expected, but winter data are few.
Large icebergs drift in a different route from smaller tabular bergs.
Why? More affected by Coriolis, also by larger base area giving more
sheear forces (all tabular bergs have similar draughts).
This is work in progress and like these penguins
we are riding a course with no clear end in sight.
Thank you for your attention!
NPI final database (30 Jan 2015)
No. Number Total Bergs Observed numbers of each size class
total
%
for
each
size class
Season
Vessel names
ships observations
bergs /obs. 10-50
50-200 200-500 500-1000 >1000 classified 10-50 50-200 200-500 500-1000 >1000
Comments
2011/12 Puerto Deseado
1
13
112 8,7
23
45
28
14
2
112 20,5 40,2
25,0
12,5
1,8
summer
2009/10 Shackleton
1
176
628 3,6
209
316
13
1
1
540 38,7 58,5
2,4
0,2
0,2
summer
2007/08 Shackleton
1
198 1642 8,3
1243
217
72
15
5
1552 80,1 14,0
4,6
1,0
0,3
summer
2006/07 Polarstern
1
853 14566 17,1
6822
4364
1867
565
112
13730 49,7 31,8
13,6
4,1
0,8 year, April-March
2005/06 Pstern Tangaroa
2
423 9019 21,3
5412
1987
846
212
80
8537 63,4 23,3
9,9
2,5
0,9
summer
2004/05 P.stern Agulhas
2
454 4053 8,9
748
696
442
338
65
2289 32,7 30,4
19,3
14,8
2,8
summer
2003/04 Shack, Agul Pstern Italica Tangaroa
5
944 6264 6,6
3096
1549
401
200
108
5354 57,8 28,9
7,5
3,7
2,0 summer + Aug, May
2002/03 Agul Pstern Shack, Explora Rongel
5
828 10659 12,9
4769
3360
1223
293
55
9700 49,2 34,6
12,6
3,0
0,6 summer+June, July
2001/02 Shack Pstern Agulhas Rongel Italica
5
688 7676 11,2
677
1480
547
315
187
3206 21,1 46,2
17,1
9,8
5,8 summer, incl. May
2000/01 Irizar Pstern Agulhas Rongel Italica Hesperides 7Unknown
956 15241 15,9
5627
3808
2363
938
268
13004 43,3 29,3
18,2
7,2
2,1 summer, incl. May
1999/2000Pstern JCR Shack Shirase Italica Gorruchaga Rongel
7
847 6325 7,5
1682
1259
597
277
66
3881 43,3 32,4
15,4
7,1
1,7
summer
1998/99 Palmer Pstyern Irizar JCR Rongel Italica Puerto 8Deseado
1143 9606 8,4
2756
2862
1549
739
402
8308 33,2 34,4
18,6
8,9
4,8 summer+May-July
1997/98 Palmer Pstern Irizar Bransfield Rongel Endurance
11 JCR1631
Inach 19027
Puerto 11,7
Deseado Marco
6788 Polo5376
Italica
2651
1146
633
16594 40,9 32,4
16,0
6,9
3,8 summer+May-July
1996/97 Bransfield Explora Pstern Italica JCR
5
370 4892 13,2
1402
892
421
322
128
3165 44,3 28,2
13,3
10,2
4,0
summer
1995/96 JCR Bransfield Irizar Aviso Castillo Puerto Deseado
7 Umitaka
537 13817
Maru Italica
11,3
6865
3934
1256
434
110
12599 54,5 31,2
10,0
3,4
0,9
summer
1994/95 Irizar Somov Bransfield JCR Explora Italica
6
916 10340 11,3
2320
2889
2173
1154
390
8926 26,0 32,4
24,3
12,9
4,4 summer, incl. May
1993/94 Pstern Agulhas Irizar Africana Hesperides Italica
7 de Teffe
654 10398 15,9
1765
1705
994
399
106
4969 35,5 34,3
20,0
8,0
2,1
summer
1992/93 A. Australis Bfield Icebird Agulhas Polarbjørn Irizar
8 de
1638
Teffe12310
Gurruchaga
7,5
2578
3496
2129
659
217
9079 28,4 38,5
23,4
7,3
2,4
summer
1991/92 Bfield JCR de Teffe Irizar Gondwana Agulhas Italica
7
771 8110 10,5
2443
2642
1537
662
164
7448 32,8 35,5
20,6
8,9
2,2
summer
1990/91 Gondwana Irizar Explora Bfield Pstern de Teffe
11Italica992
Las Palmas
8431 Aviso
8,5 Irigoyen
2392
Gorruchaga
2760Cariboo
1612
686
294
7744 30,9 35,6
20,8
8,9
3,8
summer
1989/90 Bfield Irizar Thuleland Andenes VII Brazil Agulhas
9 Columbialand
781 9961Gurruchaga
12,8
Cariboo
3540
3455
1613
583
194
9385 37,7 36,8
17,2
6,2
2,1
summer
1988/89 Somov Bfield Icebird Irizar de Teffe Shirase Arctica
12 Lady
1643Franklin
17059Prof.
10,4Viese Barken
3060 Prof.
4432
Zubov Agulhas
3131
1082
367
12072 25,3 36,7
25,9
9,0
3,0summer, incl. Oct. May
1987/88 Somov Viese Bfield Zubov Icebird Shirase de Teffe
17 Lady
2046Franklin
26514Pstern
13,0 Finnpolaris
8172 Irizar
7143
Bahia Paraiso
3689 Alm. 1559
Camara Prof.
403 Bernard
20966
Kaiyo-Mara
39,0 Agulhas
34,1
17,6
7,4
1,9
summer
1986/87 Somov Bfield Viese Irizar Pstern Glacier Bahia10
Paraiso
1391
Agulhas
24161
Aurora
17,4de Teffe
8642
7596
4062
1646
505
22451 38,5 33,8
18,1
7,3
2,2
summer
1985/86 Pstern Agulhas Zubov Glacier Bfield Endurance
10Bahia1197
Paraiso
13533
Polar 11,3
Star Irizar 4424
John Biscoe
3657
2157
813
298
11349 39,0 32,2
19,0
7,2
2,6
summer
1984/85 Capt. Myshevskij Endurance Discovery Icebird15
Nella 2009
Dan Unknown
22848 11,4
Andenes Agulhas
5687 Bahia
5708Paraiso3235
Irizar Sibex2
1069
Kaiyo Rulegi
233 Depot
15932Halley
35,7
Jantar
35,8
Bfield 20,3
6,7
1,5 summer, some Oct.
1983/84 Somov Agulhas Bfield Viese Endurance Myshevskij
16 de
2294
Teffe31520
Nella Dan
13,7Polar Sea
8486Pstern 7544
Nanok Kaiso
5090
Maru Shirase
2604 Irizar
887
Hakuhu24611
Maru 34,5 30,7
20,7
10,6
3,6
summer
1982/83 Somov Bfield Nanok Viese Zubov Polar Circle 13
Lady Franklin
806 11837
Piloto Pardo
14,7 Agulhas
2566Capt. Alcazar
2815 Polarbjørn
2224 Hero848
John Biscoe
339 Nella8792
Dan 29,2 32,0
25,3
9,6
3,9 summer, some Oct.
1981/82 Bfield Bahia Paraiso Polar Queen Fuji Agulhas Irizar,
7
Polar
489 Circle
3974 8,1
1203
1181
662
146
45
3237 37,2 36,5
20,4
4,5
1,4
summer
1980/81 John Biscoe
1
33
40
0
0
0
3
37
40
0,0
0,0
0,0
7,5
92,5
summer
1979/80 Bransfield
1
22
22
0
0
0
3
19
22
0,0
0,0
0,0
13,6
86,4
summer
1978/79 Bransfield Agulhas Polarsirkel Yelco
4
208 2342 11,3
970
628
179
95
18
1890 51,3 33,2
9,5
5,0
1,0
summer
1976/77 Polarsirkel
1
159 1873 11,8
0
0
0
0
0
0
summer
Total sums
223 28110 338800 12,1 106367
89796
48763
19820 6738
271484 39,2 33,1
18,0
7,3
2,5
April
May
June
July
August
September
October
May-Sept
Winter, April-Oct
Summer
1844 16222 8,8
401 3215 8,0
156
818 5,2
182
427 2,3
92
103 1,1
139
429 3,1
466 3459 7,4
970 4994 5,1
3295 24706 7,5
24815 314094 12,7
3936
917
239
245
38
72
1369
1511
6805
99562
4165
987
444
156
61
71
709
1719
6576
83220
2454
643
63
17
3
105
539
831
3849
44914
888
200
3
1
0
7
246
211
1346
18474
315
76
2
1
0
5
103
84
500
6238
11758
2823
751
420
102
260
2966
4356
19076
252408
33,5
32,5
31,8
58,3
37,3
27,7
46,2
34,7
35,7
39,4
35,4
35,0
59,1
37,1
58,8
27,3
23,9
39,5
34,5
33,0
20,9
22,8
8,4
4,0
2,9
40,4
18,2
19,1
20,2
17,8
7,6
7,1
0,4
0,2
0,0
2,7
8,3
4,8
7,1
7,3
2,7
2,7
0,3
0,2
0,0
1,9
3,5
1,9
2,6
2,5
ceberg statistics on NPI final database (3 July 2015)
Number
Sector
observ
⁰ - 44⁰ 59 W
9694
5⁰ - 89⁰ 59W
7334
0⁰ - 134⁰ 59W
471
35⁰ - 180⁰ W
963
80⁰ - 135⁰E
1661
34⁰ 59 - 90⁰E
1585
9⁰ 59 - 45⁰E
2564
4⁰ 59 - 0⁰E
3838
otals
28110
Total Bergs Observed numbers of each size class
total
%
for
each
size class
bergs /obs.
10-50
50-200 200-500 500-1000 >1000 classified 10-50 50-200 200-500 500-1000 >1000
115322
11,9
38940
32253
16591
6753 2420
96957 40,2 33,3
17,1
14,4
2,5
117168
16,0
45492
30111
15145
5580 1612
97940 46,4 30,7
15,5
5,7
1,6
8397
17,8
1503
2157
1294
469
164
5587 26,9 38,6
23,2
8,4
2,9
10951
11,4
2424
3288
1698
724
302
8436 28,7 39,0
20,1
8,6
3,5
10381
6,2
2499
2369
1695
996
501
8060 31,0 29,4
21,0
12,4
6,2
25686
16,2
4532
5638
3892
2088
795
16945 26,7 33,3
23,0
12,3
4,7
32310
12,6
5577
7955
5676
2150
706
22064 25,3 36,1
25,7
9,7
3,2
18828
4,9
5400
6025
2682
1060
238
15405 35,1 39,1
17,4
6,9
1,5
339043
12,1 106367
89796
48673
19820 6738
271394 39,2 33,1
17,9
7,3
2,5
0 - 74 59W
10680 154202
5 - 159 59W
1110 19083
60W-160E
1944 13090
59 59E - 30E
4693 60354
9 59E - 29 59W 9683 92071
ontrol
14,4
17,2
6,7
12,9
9,5
58703
3575
3580
10459
30250
40378
4497
3488
14213
27220
20441
2691
2129
10120
13382
7770
1025
1026
4576
5423
2328
392
534
1602
1882
129620
12180
10757
40970
78157
271684
45,3
29,4
33,2
25,5
38,7
31,2
36,9
32,4
34,7
34,8
15,8
22,1
19,8
24,7
17,1
6,0
8,4
9,5
11,1
6,9
1,8
3,2
5,0
3,9
2,4
00 - 135W
19,0
1266
1980
1144
471
150
5011
25,3
39,5
22,9
9,4
3,0
390
7397