The work described in this poster & the research leading to these results has received funding from the European Community's Seventh Framework Programme FP7/2007-2013 – Marie-Curie ITN, under grant agreement n° 238512, GATEWAYS project.Acknowledgements to Saskia Kars for help with SEM images.
2b
Fossil planktonic foraminifera from the Agulhas region over the last Glacial-Interglacial cycle:
1, Frank Peeters1, Margit H. Simon2, Ian R. Hall2, Thibaut Caley1 2 (1) Earth and Climate, Faculty of Earth and Life Sciences, VU University Amsterdam, The Netherlands
(2) School of Earth and Ocean Sciences, Cardiff University, Cardiff, United [email protected]
Aims
Agulhas Leakage Efficiency and Polar Fauna Similarity
Figure 1:
downcore, with 1.0 meaning the fauna in both cores is excactly the same, while 0 means completely dissimilar samples. A similar fauna suggests the STF is south of core MD02-2588, while a dissimilar
ApproachForaminifer abundance counts show glacial-interglacial variability in the
Basin Record (1) to this record from the Indian Ocean, described as the
upstream variability (fig. 1). Comparisons of local faunal changes at the
(based on (3)) are used to compare the local faunal assemblages (fig. 1).
Conclusions
The similarity comparison of the polar fauna between cores MD02-2588 and CD154
Figure 4: The Lisieki Raymo benthic isotope stack is used here for reference, to show the Marine Isotope Stages over the last 100 ka. The tropical-subtropical fauna (fig. 5) is shown for the three core sites (CD154 17-17K, MD02-2588 and CBR). This fauna is referred to as the Agulhas Leakage Fauna (ALF) at site CBR. The subpolar-polar fauna for each site is also shown (fig. 5). Glacial-
Figure 3:
adapted from (4), (2), and (5). The Agulhas Current is represented by ACby AR, Agulhas return current by ARC, Mozambique Current by MC, East Madagascar Current by EMC, Red Sea Intermediate Water by RSIW, Benguela Undercurrent by BU, and the North Brazil Current by NBC. CD154 17-17K shows the ‘typical’ upstream foraminifer assemblages of the
CD154 17-17KCBR
MD02-2588
The StoryForaminifer assemblages have been used in the past as a proxy for paleo-leakage (commonly known as the Agulhas Leakage Fauna, or ALF) (1). Normalizing the ALF to the upstream Agulhas Current fauna can provide increased accuracy in the assessment of the leakage, as it takes
the south by the migratory Subtropical Front (STF) (fig. 3), which moves
Agulh
as C
urre
nt
Subtropical Front
Agulh
as C
urre
nt
Subtropical Front
Interglacial (e.g. Holocene)
Glacial (e.g. LGM)
Figure 2:
G A T E W A Y SInitial Training Network
References
-minifera deep-sea sediments.” 11(1): 15-35.
Figure 5: The tropical-
and the subpolar-polar fauna (right).
0
10
20
30
40
50
60
70
80
20
40
60
80
100
Age (ka)
anua
f lac
iport
bus -
lac
ipor
T)
%( )a
nuaF
sah
lug
A(
)%( anuaF r al o
P - r al opbuS
2.5
3
3.5
4
4.5
5
5.5
2 4
T-1
0 20 40 60 80 100
0
)o%(
O81d ar efi nimar of ci ht ne
B40
RL
mor
ele
ss
more
less
CD154 17-17K
CD154 17-17K
MD02-2588
MD02-2588CBR
CBR
0
0.2
0.4
0.6
0.8
0 20 40 60 80 100
Polar fauna sim
ilaritybetw
een CD
154 17-17Kand M
D02-2588
1.0
Age (ka)
0
0.1
0.2
0.3
0.4
Agu
lhas
Lea
kage
Effi
cenc
y 0.52 4
T-1
mor
ele
ss
more
lesssouth STF north
To show the upstream glacial-interglacial variability in the Agulhas Current foraminifer assemblages and the influence this has on the downstream