Download 06_Oceanic records

The ocean-atmosphere system:
primary responses to orbital forcings
Orbital forcings
GLACIAL
OCEAN
INTERGLACIAL
temperature
humidity
CO2
winds
volume
temperature
CO2
currents
The oceanic
d18O record:
80-90% RSL
response;
10-20%
temperature
response?
SST changes
from LGM to
present in
coastal
waters of N.
California
(~100 km offshore?)
Radiolarian assemblages in core 1019
(989 m water depth)
YD
green line = GISP2 d18O record; black line=radiolarian record
Primary productivity and
zones of coastal upwelling
image: terra.nasa.gov
Pelagic diatom assemblages of the N. Pacific
(e.g. Okhotsk Sea cluster = one of three
subarctic water masses, shown in black)
V20-119
580
RC10-216
V21-172
V20-107
579
from: Sancetta & Silvestri (1986) Paleoceanography 1, 163-180.
“Okhotsk
cluster”
through
time
from: Rohling et al. (1998) Nature, 394, 162-165.
RSL -temperature - salinity
interactions in the Red Sea
Low RSL = hypersaline Red Sea = no planktonic forams
ooze
H - layer
(ooze-filled
burrows?)
A
Heinrich
layer
(H-1)
in a
deep-sea
core
Iceberg-rafted detritus
(IRD) in H1
Heinrich events in the North
Atlantic Ocean
Oceanographic effects of
drifting icebergs
drift
cold fresh water
>200 m
nutrient-rich
nutrientdeficient
detritus
Heinrich
(5-10 ka)
events and
Bond
cycles
(~1.5 ka)
in VM23-81
N. Atlantic currents:
iceberg-drift routes
The N. Atlantic ‘gate’ and the ‘bingepurge’ cycle of the Laurentide ice sheet
Ocean
‘polar front’
cold
warm
Dansgaard-Oeschger cycles and Heinrich events
Thermohaline circulation
Binge and purge: is there a Heinrich
record in Antarctica?
antiphasing?
SST C(org)%
Inferred
Late
Glacial
and
Holocene
SST
(Aegean
Sea)
YD
H1
from: Geraga et al., (2000), Palaeo3, 156, 1-17
Sapropel stratum
in a core from the
eastern
Mediterranean
(“sapro” = putrid refers to high Corg
content);
“pel” = mud
S1
Episodes of
sapropel
formation in
the last
200 000 years
in the eastern
Mediterranean
from: Kallel et al., (2000),
Palaeo3, 157, 45-58
S3 S4 S5
30°N
S6 S7
Laminated sapropel deposits
from: Kemp et al., (1999), Nature, 398, 57-61
Sapropels:
annually
laminated
diatom
mats
from: Kemp et al., (1999),
Nature, 398, 57-61
Sapropel formation hypothesis
after Kemp et al., (1999), Nature, 398, 57-61.
(see Sancetta (1999), Nature 398, 27-29 for discussion)
• Greater freshwater runoff to eastern Mediterranean
(heavy rainfall in Nile headwaters and in Med. Basin); leads
to:
• Enhanced stratification of surface waters, produces ‘nutricline’
across surface halocline; leads to:
• Massive bloom of diatoms adapted to stratified waters (chiefly
Rhizosolenia spp. and Hemiaulus hauckii).
• Winter mixing of water column causes mass sinking of diatom
mats.
• Mixing brings nutrients to surface, promoting conventional nearsurface winter blooms of mixed diatoms.
Freshwater sources in the
Mediterranean
base map from: Kallel et al., (2000), Palaeo3, 157, 45-58
Sapropels and climate of the
Nile basin
Eastern Mediterranean sedimentary record*
“sapropelic”
S1a
11
10
arid
9
8
wet
S1b
7
6
5
4
3
2
1
arid
Eastern Saharan sedimentary
and archaeological record**
* Geraga et al., (2000), Palaeo3, 156, 1-17
** Malville et al., (1998), Nature 392, 488-491
0 ka BP
Location
of core
74 KL in
the
Arabian
Sea
18
d O,
74 KL:
dust deposition
and CaCo3 production
Dust
minimum
7850
8850
Sahara dust storm over
adjacent Atlantic Ocean
image: terra.nasa.gov
Dust accumulation and palaeoproductivity
(core Meteor 12392: on continental rise
offshore of Spanish Sahara)
Japan Sea dust record
Dust source: Mongolia/N. China
Iron fertilization experiment:
polar Southern Ocean (I)
days
Iron fertilization experiment:
polar Southern Ocean (II)
Mechanisms of CO2 drawdown
CO2 drawdown (Vostok)
Iron fertilization experiment:
polar Southern Ocean (III)
DMS makes clouds “brighter
than white”
from: Charlson et al., (1987) Nature 326, 655-661
Points to consider
Ocean/atmosphere temperature - CO2 - sea ice
feedbacks.
Continental climates and oceanic responses:
dust exports and palaeoproductivity;
monsoonal rains and sapropels;
glacial surging and THC switching.
Palaeoproductivity patterns: consider effects of
currents, RSL and marine food chains.