The ocean-atmosphere system: primary responses to orbital forcings

The ocean-atmosphere system: primary responses to orbital forcings

The ocean-atmosphere system: primary responses to orbital forcings Orbital forcings GLACIAL INTERGLACIAL temperature humidity

CO2 winds ATMOSPHERE OCEAN 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) YDT1 green line = GISP2 18O 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. Okhots k 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 H - layer (ooze-filled ooze burrows?)

pelagic ooze A Heinrich layer (H-1) in a deepsea core

Iceberg-rafted detritus (IRD) in H1 Heinrich events in the North Atlantic Ocean Oceanographic effects of drifting icebergs

drift cold fresh water nutrientdeficient >200 m nutrient-rich detritus

Heinrich (5-10 ka) events and Bond cycles (~1.5 ka) in VM2381 N. Atlantic currents:

iceberg-drift routes The N. Atlantic gate and the bingepurge cycle of the Laurentide ice sheet cold Ocean polar front

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 Mediterranea n from: Kallel et al., (2000), Palaeo3, 157, 45-58 30N S3 S4 S5

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 Freshwater sources in the Mediterranean

base map from: Kallel et al., (2000), Palaeo3, 157, 45-5 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 arid Eastern Saharan sedimentary

and archaeological record** * Geraga et al., (2000), Palaeo3, 156, 1-17 ** Malville et al., (1998), Nature 392, 488-491 1 0 ka BP Location

of core 74 KL in the Arabian Sea 74 KL: 18O, 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

from: Boyd et al., (2000), Nature 407, 695-702. 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.

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