orbital forcings the ocean-atmosphere system: primary responses to orbital forcings atmosphere ocean...
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Orbital forcings
The ocean-atmosphere system:primary responses to orbital
forcings
ATMOSPHERE
OCEAN
temperaturehumidity
CO2winds
GLACIAL
volumetemperature
CO2currents
INTERGLACIAL
The oceanic d18O record:
80-90% RSL response;10-20%
temperatureresponse?
SST changes
from LGM to present in coastal
waters of N. California
(~100 km offshore?)
Radiolarian assemblages in core 1019 (989 m water depth)
green line = GISP2 18O record; black line=radiolarian record
T1YD
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)
from: Sancetta & Silvestri (1986) Paleoceanography 1, 163-180.
579
580
V20-119
V20-107
V21-172RC10-216
“Okhotsk
cluster” through
time
RSL -temperature - salinity interactions in the Red Sea
Low RSL = hypersaline Red Sea = no planktonic forams
from
: R
ohlin
g e
t al. (
1998)
Natu
re,
394,
162-1
65.
A Heinrich
layer (H-1) in a
deep-sea core
pela
gic
ooze
ooze
H -
layer
(ooze
-fille
d b
urr
ow
s?)
Iceberg-rafted detritus (IRD) in H1
Heinrich events in the North Atlantic Ocean
Oceanographic effects of drifting icebergs
>200 m
drift
cold fresh water
nutrient-deficient
nutrient-rich detritus
Heinrich (5-10 ka) events
and Bond cycles
(~1.5 ka)in VM23-
81
N.
Atl
anti
c cu
rrents
:ic
eberg
-dri
ft r
oute
s
The N. Atlantic ‘gate’ and the ‘binge-purge’ 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?
Inferred Late
Glacial and
Holocene SST
(Aegean Sea)
from: Geraga et al., (2000), Palaeo3, 156, 1-17
YD
H1
SST C(org)%
Sapropel stratum in a core from the eastern
Mediterranean
(“sapro” = putrid - refers to high Corg content); “pel” = mud
Episodes of sapropel
formation in the last 200 000
years in the eastern
Mediterranean
from: Kallel et al., (2000), Palaeo3, 157, 45-58
S1 S3 S4 S5 S6 S7
30°N
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 hypothesisafter 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 near- surface 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
S1a S1b
“sapropelic”Eastern Mediterranean sedimentary record*
Eastern Saharan sedimentary and archaeological record**
* Geraga et al., (2000), Palaeo3, 156, 1-17** Malville et al., (1998), Nature 392, 488-491
arid wet arid
11 10 9 8 7 6 5 4 3 2 1 0 ka BP
Location of core74 KL in
the Arabian
Sea
74 KL: 18O, dust deposition and CaCo3
production
Dust minimum
78508850
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
from
: B
oyd e
t al., (2
00
0),
N
atu
re 4
07
, 6
95
-70
2.
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 considerOcean/atmosphere temperature - CO2 - sea
icefeedbacks.
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.