Scientific Ocean Drilling Accomplishments and Challenges (2011) / Chapter Skim
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4 Scientific Accomplishments: Earth's Climate History
4 Scientific Accomplishments: Earth's Climate History
Pages 39-54
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From page 39... ...
understanding of dramatic and continuous change in Earth's expeditions have focused on many aspects of environmental climate system over the past ~100 myr, from extremes of processes and change, including global-scale orbital climate expansive warmth with ice-free poles to massive continental forcing; processes and thresholds of Northern Hemisphere ice sheets and polar ice caps. Significantly, these records and Antarctic glaciations and global sea level change; abrupt of millions to tens of millions of years ago provide critical millennial-scale climate change; and past global warmth and insights into environmental changes when atmospheric CO2 extreme climate events.
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From page 40... ...
, particularly when applied to older sediments. implies global sea levels more than 60 m higher than the Nevertheless, as laboratory studies continue and present, when atmospheric CO2 levels may have been as high calibrations improve, there has been significant con vergence between different proxies used to estimate as 2,000-4,000 ppm (Pagani et al., 2005b; also discussed in temperature and pCO2 (e.g., Beerling and Royer, the following section)
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From page 41... ...
show Spatial coverage of ocean records of past extreme warm complete deglaciation of the Greenland and West Antarctic intervals is biased toward the North Atlantic and East Pacific, ice sheets and the low elevation margins of the East Antarctic leaving large swaths of the ocean floor to be sampled. Conice sheet, with global sea levels up to 20 m higher than the sequently, sea surface temperature datasets for these times present (Miller et al., 2011; Raymo et al., 2011)
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From page 42... ...
180˚ 15 0˚ 0˚ 15 0˚ 12 12 0˚ 90˚W 90˚E ˚ 60 60 ˚ ODP Leg 151 Leg 163 30 ˚ 30 ˚ IODP Exp 302 0˚ b) 40˚ DSDP N Leg 28 ODP 20˚ Leg 113 Leg 119 Leg 120 0˚ Leg 188 Leg 189 -20˚ IODP Exp 318 -40˚ -60˚ -80˚ 30˚ 60˚ 90˚E 120˚ 150˚ 180˚ 150˚ 120˚ 90˚W 60˚ 30˚ 0˚ 30˚ FIGURE 4.2 Location maps of DSDP, ODP, and IODP expeditions in polar regions that were related to past climate extremes.
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From page 43... ...
–1.0 Southern Ocean The sudden disruption in the carbon cycle -- nearly 690 Central Paci c equivalent to burning modern fossil fuel reserves -- –2.0 865 b –1.0 14 South Atlantic produced significant ocean acidification, disrupted 525 527 the deep ocean ecosystem, and caused significant Temperature (°C) –0.5 12 evolutionary turnover in benthic dwelling foramin δ18O ( ‰)
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From page 44... ...
, which Changes in global sea level over the past 40 myr reflect confirmed climatic patterns observed in global ice volume the evolution of polar ice sheets from ephemeral, small- proxy records from scientific ocean drilling oxygen isotope medium Antarctic ice sheets (prior to 33.5 myr) to a large records (e.g., ODP Leg 120, Zachos et al., 1996; ODP Leg Antarctic ice sheet and variably sized Northern Hemisphere 154, Zachos et al., 2001b; ODP Leg 199, Pälike et al., 2006)
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From page 45... ...
(A) Global sea level curve from continental margin cores, which represent changes in sea level in response to polar ice volume fluctuation (e.g., Miller et al., 2005; Kominz et al., 2008)
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From page 46... ...
ODP Legs 150,174A, and 150X/174AX ability and sea level changes will remain a challenge, because sampled the slope, outer shelf, and onshore, respectively; it requires integrated onshore and offshore drilling transects dated unconformities produced during sea level fall; and cor- on continental margins and core retrieval over multiple timerelated them to increases in δ18O values indicative of periods frames and depositional settings, including difficult drilling of polar ice volume growth. More than 30 oscillations in environments such as sea ice and unconsolidated sediments.
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From page 47... ...
and high-latitude locations calculated changes in Earth's energy budget due to orbital of all ocean basins (ODP Leg 145 in the North Pacific; ODP variability and albedo changes, and the observed magnitude Legs 151, 162, and 172 in the North Atlantic; ODP Leg 177 of climate and ice volume changes. This conclusion would in the Southern Ocean; ODP Leg 181 in the western South not be possible without the ability to link marine, land-based, Pacific; ODP Leg 188 in Prydz Bay; and ODP Leg 202 in and ice core records of climate and CO2.
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From page 48... ...
The broad impact of the development of this The fundamental understanding of how Cenozoic climate chronology can be observed in terrestrial-based studies of evolved has also provided a framework to evaluate the effects archeology, anthropology, and climate, including the com- of changing climate on evolution, including hominins. parison of major human evolutionary events with changes in Scientific ocean drilling did not provide the first eviclimate based on marine oxygen isotope records from ODP dence for orbital forcing of climate, but without the developsites (e.g., deMenocal, 2011; see section on "Co-evolution ment of long, continuous, undisturbed sedimentary sections, of life and the planet" at the end of this chapter)
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From page 49... ...
The more temperature, a sharp rise in atmospheric CO2, polar ice sheet modern JOIDES Resolution helped to increase the collapse, and a rise in global sea level. A better understand- overall core recovery and revolutionized deepwater ing of how these systems interacted will provide important coring practices (see white papers from Dennis Kent and Ted Moore, Appendix C)
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From page 50... ...
understanding the far-field effects of North Atlantic changes (1994) extended the ice-rafted debris record at the same site at this time by acquiring cores from sites with high sedi(DSDP Site 609)
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From page 51... ...
During periods of higher ice-rafted debris scale climate changes implies that ocean-atmosphere reor- input and greater freshwater delivery into the North Atlantic, ganizations happen quickly and have widespread impact on colder air temperatures prevailed over Greenland and colder temperature and moisture patterns in and beyond much of sea surface temperatures were found in the high-latitude the Northern Hemisphere. North Atlantic.
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From page 52... ...
As shown in rates has lacked geographic coverage and is strongly biased Late Triassic (228 myr ago) to recent records in marine seditoward the North Atlantic.
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From page 53... ...
. These records show that have been investigated by examination of scientific ocean North Africa's continental aridity tracked cold North Atlantic drilling cores, notably the δ13C anomaly (DSDP Site 524; sea surface temperatures associated with Northern HemiODP Leg 207; DSDP Sites 528 and 577; ODP Site 1001A; sphere glaciations, while East Africa's aridity was influenced Hsü et al., 1982; Hsü and McKenzie, 1985; D'Hondt et more by Indian Ocean sea surface temperature (NRC, 2010)
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From page 54... ...
Although tion. Finally, the effects of the evolution of new life forms some initial discoveries, such as the K-T impact, occurred and new physiological modalities on biogeochemical cycles on land, deeper understanding was achieved by the contex has not been examined in scientific ocean drilling studies; tual approach provided by sediments preserved in the ocean organisms and their physiology are a first-order control on basins.
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