1
Auxiliary Material
Method used to compute air temperature and averaged PAR in Figure 1:
Air temperatures for each month were taken from NCEP-NCAR reanalyses [Kalnay et al.,
1996] and averaged over the Antarctic sea ice zone and over the 1983–2007 period,
excluding points for which ice concentration was below 15%. Ice concentration data were
taken from EUMETSAT-OSISAF [2010]. A mean seasonal cycle (1983–2007) of incoming
PAR at the ice surface was computed, using the method described in Vancoppenolle et al.
[2011], which is only given in summary here. We started from downwelling shortwave
radiation flux incoming at the ice surface Fsw(,,d), for each day d, longitude  and latitude
. Fsw was computed by integrating over a diurnal cycle the formula of Shine [1984], giving
Fsw as a function of day of year, time of the day, latitude, cloud fraction and water vapor
pressure. Cloud fractions [Berliand and Strokina, 1980] and relative humidities [Trenberth et
al., 1989] were taken from spatially-varying monthly mean climatologies. Relative humidity
was converted to water vapour pressure using daily mean 1983–2008 NCEP air temperatures.
We then converted to PAR(,,d) using PAR = 2.33 x Fsw. Values were averaged over the sea
ice zone for each month, using the same procedure as for temperature.
Method used to compute the probabilities in Figure 3:
chli,k is the chlorophyll concentration value, interpolated on a 5 layer vertical grid, for profile
i and layer k=1, …, 5. The vertical average for ith profile is denoted by chlimean. Each core has
a core length hi. l=1, …, 5 thickness categories are used with boundaries [Hl-1, Hl]. The
boundaries of core length categories, Hl (l=0, …, 5) are chosen as: [0, 0.4, 0.7, 1, 2, 99]. Xi,k,l
is equal to one both if chli,k > 1.5 x chlimean and if Hl-1 ≤ hi < Hl; it is equal to zero otherwise.
The probability of finding a maximum for layer k and category l, Pk,l, is defined as:
2
Np
Equation 1:
Pk,l   X i,k,l
i1

Np
5
 X
i1 k 1
i,k,l
3
Table S1. List of voyages compiled in the ASPeCt – Bio database. *Cores refers to the
number of integrated chl-a profiles collected during a voyage.
Voyage ID
AMERIEZ 83
Region/Sector
Weddell East
Year
1983
Months
Cores*
Nov – Dec 13
AMERIEZ 86
Weddell West
Weddell East
Weddell East
Weddell East
Amundsen/
Bellingshausen
Weddell West
Weddell West
Weddell East
Weddell West
Weddell East
Weddell East
Weddell West
Weddell East
Weddell West
Weddell East
Amundsen/
Bellingshausen
Indian/Pacific
Ross Sea
1986
Apr – May 9
1986
1986
1987
Jun – Sep
Sep – Dec
Jun – Jul
31
54
44
References
Ainley & Sullivan, 1984
Garrison & Buck, 1991
Sullivan & Ainley, 1987
Garrison & Buck, 1989
Schnack-Schiel, 1987
Schnack-Schiel, 1987
Quetin & Ross, 1988
1988
1988
Oct – Nov
Oct – Dec
21
45
Hempel, 1989
Garrison & Close, 1993
1989
Sep – Oct
40
Augstein et al., 1991
1991
1992
1992
1992
Mar
Mar – Apr
Apr – May
Jun – Jul
20
9
19
40
Bathmann et al., 1992
Melnikov, 1998
Spindler et al., 1993
Lemke, 1994
1994
Jan – Mar
30
Miller & Grobe, 1996
1997
1998
17
28
Garrison et al., 2005
Pacific
Ross Sea
Ross Sea
Amundsen/
Bellingshausen
Amundsen/
Bellingshausen
Amundsen/
Bellingshausen
Pacific
Amundsen/
Bellingshausen
Pacific
1998
1998
1999
2001
Oct
May –
June
Nov
Nov – Dec
Jan
Apr
5
82
25
3
Trevena & Jones, 2006
Arrigo et al., 2003
Garrison et al., 2005
Meiners et al., 2004
2001
Jul – Aug
74
Fritsen et al., 2008
2001
Jul – Aug
33
Fritsen et al., 2008
2001
2002
Oct – Nov
Aug – Sep
19
137
Fritsen et al., 2008
2002
Oct – Nov
42
Aug – Sep
86
AURORA 03-V1
Amundsen/
2002
Bellingshausen
Pacific
2003
Sep – Oct
138
AURORA 04-V1
Pacific
Oct – Nov
62
ANT V/2
ANT V/3
WINCRUZ 87
ANT VII/2
AMERIEZ 88
ANT VIII/2
ANT IX/3
ISW
ANT X/3
ANT X/4
ANT XI/3
AURORA 97-V2
NBP-9803
AURORA 98-V4
ROAVERRS 98
NBP-9901
ANT XVIII/5b
LMG-0106
NBP-0104
AURORA 01-V1
LMG-0205
AURORA 02-V1
NBP-0204
2004
McMinn et al., 2007
Pankowski & McMinn, 2008
Fritsen et al., 2008
McMinn et al., 2007
Lannuzel et al., 2007
Becquefort et al., 2009
McMinn et al., 2007
4
Nov – Jan
56
Lannuzel et al., 2008
Weddell West
2004/
2005
2006
Sep – Oct
31
Meiners et al., 2009
AURORA 07-V1
Pacific
2007
Sep – Oct
53
NBP-0709
Amundsen/
2007
Bellingshausen
Amundsen/
2008
Bellingshausen
& Ross Sea
Oct
20
Meiners et al., 2011
van der Merwe et al., 2009
van der Merwe et al., 2011
Fritsen et al., 2011
Dec
14
Fransson et al., 2011
ANT XXII/2
Weddell West
ANT XXIII/7
OSO-08
5
Acknowledgments (auxiliary material)
KM acknowledges support by the Australian Antarctic program through AAS grant #2767.
MV acknowledges support by EU-FP7 project BISICLO and ASPeCt. DNT is grateful for
funding from NERC, The Royal Society, The Leverhulme Trust and The Nuffield
Foundation. KS acknowledges ARC Discovery project 0209308 and AAS grant #1328.
This paper has benefited from Belgian funding through the Communauté Française de
Belgique (SIBCLIM - ARC n° 02/07-287), the Fonds National de la Recherche Scientifique
(BASICS - FRFC n° 2.4649.07) and the Belgian Science Policy Ofice (BIGSOUTH BELSPO n° SD/CA/05A). We thank Stathys Papadimitriou, Louiza Norman, Christian Haas,
Erika Allhusen, Cynthia Chen, Katherine Tattersall and many others for their help with
chlorophyll a analysis and support in the field.
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