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(a)
(b)
(c)
115 - 125 ka BP Change:
Annual P-E
115 - 125 ka BP Change:
Annual Runoff
115 - 125 ka BP Change:
Upper Ocean Salinity
20°N
20°N
20°N
12°N
9°N
5°N
0°
0°
0°
20°S
20°S
20°S
80°W
60°W
40°W
80°W
60°W
40°W
80°W
60°W
40°W
(d)
(e)
(f)
115 - 125 ka BP Change:
Ocean Transport
River Discharge Impact on
Upper Ocean Salinity
River Discharge Impact on
February Mix
e
d Layer Depth
20°N
20°N
0°
0°
20°S
20°S
40°W
80°W
60°W
40°W
80°W
60°W
Fig. 1 Changes in South American climate from 125 to 115 ka BP (a
-
d). a Changes in total
annual net precipitation (precipitation
-
evaporation), b changes in runoff, c change in upper ocean
(0
-
150 m) salinity, d changes in water column integrated oceanic transport.
Impact of
115
125 ka BP
upper ocean salinity change due to river runoff, f changes in February mixed layer depth in high
northern latitudes linked to river discharge increase from 125 to 115 ka BP. Black dots show the
locations of marine sediment cores (see caption of Fig.
2
for details)
-
125 ka BP changes in South American river discharge (e
-
f). e Fraction of 115
-
equilibrate for 700 years. Two additional simulations were performed with
115 ka BP boundary conditions to isolate the impact of changes in river discharge,
i.e. with South American river
ow
fixed to 115 or 125 ka BP conditions.
3 Key Findings
The sedimentary geochemical composition con
N
exclusively receive sediments from the Amazon River, while the Orinoco and
Amazon Rivers both contribute to terrigenous input at 12
rms that sites at 5
°
N and 9
°
°
N (Govin et al.
2014
).
Cores at 5
N exhibit a progressive increase in the relative proportion of
Andean material between 126 and 111 ka BP (Fig.
2
). It re
°
N and 9
°
ects the increasing input
of detrital particles from Andean regions, where most of Amazon terrigenous
material originates (Guyot et al.
2007
), and agrees with the higher precipitation and
runoff simulated over most of the Amazon basin at 115 ka BP compared to 125 ka BP
(Fig.
1
a, b). This result also agrees with western Amazonian speleothem records that
suggest strong coupling between the intensity of the South American monsoon and
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