The ocean-atmosphere system: primary responses to orbital forcings

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The ocean-atmosphere systemprimary responses to
orbital forcings
Orbital forcings
GLACIAL
INTERGLACIAL
temperature humidity CO2 winds
ATMOSPHERE
OCEAN
volume temperature CO2 currents
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The oceanic d18O record80-90 RSL
response10-20 temperatureresponse?
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SST changesfrom LGM to present in coastal waters
of N. California(100 km offshore?)
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Radiolarian assemblages in core 1019 (989 m water
depth)
YD
T1
green line GISP2 d18O record black
lineradiolarian record
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Primary productivity and zones of coastal
upwelling
image terra.nasa.gov
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Pelagic diatom assemblages of the N. Pacific
(e.g. Okhotsk Sea cluster one of three
subarctic water masses, shown in black)
RC10-216
V20-119
V21-172
580
V20-107
579
from Sancetta Silvestri (1986)
Paleoceanography 1, 163-180.
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Okhotskcluster through time
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RSL -temperature - salinity interactions in the
Red Sea
from Rohling et al. (1998) Nature, 394, 162-165.
Low RSL hypersaline Red Sea no planktonic
forams
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A Heinrich layer (H-1) in a deep-sea core
pelagic ooze
H - layer (ooze-filled burrows?)
ooze
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Iceberg-rafted detritus (IRD) in H1
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Heinrich events in the North Atlantic Ocean
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Oceanographic effects of drifting icebergs
drift
cold fresh water
nutrient-deficient
gt200 m
nutrient-rich
detritus
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Heinrich (5-10 ka) events and Bond cycles (1.5
ka)in VM23-81
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N. Atlantic currentsiceberg-drift routes
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The N. Atlantic gate and the binge-purge
cycle of the Laurentide ice sheet
cold
Ocean polar front
warm
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Dansgaard-Oeschger cycles and Heinrich events
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Thermohaline circulation
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Binge and purge is there a Heinrich record in
Antarctica?
antiphasing?
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Inferred Late Glacial and Holocene SST(Aegean
Sea)
SST C(org)
YD
H1
from Geraga et al., (2000), Palaeo3, 156, 1-17
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Sapropel stratum in a core from the eastern
Mediterranean (sapro putrid - refers to
high Corg content) pel mud
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Episodes of sapropel formation in the last 200
000 years in the eastern Mediterranean
S1 S3 S4 S5 S6 S7
30N
from Kallel et al., (2000), Palaeo3, 157, 45-58
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Laminated sapropel deposits
from Kemp et al., (1999), Nature, 398, 57-61
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Sapropelsannually laminated diatom mats
from Kemp et al., (1999), Nature, 398, 57-61
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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 near- surface winter blooms of
  mixed diatoms.

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Freshwater sources in the Mediterranean
base map from Kallel et al., (2000), Palaeo3,
157, 45-58
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Sapropels and climate of the Nile basin
Eastern Mediterranean sedimentary record
sapropelic
S1a S1b
11 10 9 8 7 6 5 4
3 2 1 0 ka BP
arid wet
arid
Eastern Saharan sedimentary and archaeological
record
Geraga et al., (2000), Palaeo3, 156, 1-17
Malville et al., (1998), Nature 392, 488-491
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Location of core74 KL in the Arabian Sea
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74 KL d18O, dust deposition and CaCo3 production
Dust minimum7850 8850
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Sahara dust storm over adjacent Atlantic Ocean
image terra.nasa.gov
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Dust accumulation and palaeoproductivity (core
Meteor 12392 on continental rise offshore of
Spanish Sahara)
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Japan Sea dust record
Dust source Mongolia/N. China
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Iron fertilization experimentpolar Southern
Ocean (I)
days
from Boyd et al., (2000), Nature 407, 695-702.
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Iron fertilization experimentpolar Southern
Ocean (II)
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Mechanisms of CO2 drawdown
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CO2 drawdown (Vostok)
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Iron fertilization experimentpolar Southern
Ocean (III)
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DMS makes clouds brighter than white
from Charlson et al., (1987) Nature 326, 655-661
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Points to consider
Ocean/atmosphere temperature - CO2 - sea
icefeedbacks.
Continental climates and oceanic responsesdust
exports and palaeoproductivitymonsoonal rains
and sapropelsglacial surging and THC switching.
Palaeoproductivity patterns consider effects of
currents, RSL and marine food chains.