Borehole Observatory Installations on IODP Expedition 306 Reconstruct Bottom-Water Temperature Changes in the Norwegian Sea

Harris, R. N.

doi:10.2204/iodp.sd.2.03.2006

Cited by 9 publications

(6 citation statements)

References 18 publications

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“…As a second important objective of Expedi tion 306, a borehole observatory for measure ments of sub-bottom temperatures for longterm reconstruction of bottom-water temperatures was installed successfully in a newly drilled 180-meter-deep hole close to the Ocean Drilling Program's Site 642 (see Figure 1: Site U1315). By analyzing sub-bottom tem perature perturbations, a temperature record may be able to be reconstructed for the first time of bottom water during at least the past 100 years, i.e., going back in time far beyond the directly measured temperature records available up to now [Harris et al, 2006].…”

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confidence: 99%

North Atlantic paleoceanography: The last five million years

Stein

Kanamatsu²,

Alvarez-Zarikian

et al. 2006

EoS Transactions

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In the North Atlantic, cold, relatively salty water sinks in the icy Labrador and Greenland seas, forming North Atlantic Deep Water (NADW).This circulates through the global ocean, driving ocean overturning and global heat transport and, thus, impacting global climate. As one of the most climatically sensitive regions on Earth, the North Atlantic has experienced abrupt changes to its oceanatmosphere‐cryosphere system, triggered by fluctuations in meltwater delivery to source areas of NADW formation. For about the past 100 thousand years, these abrupt jumps in climate state have manifested as ‘Dansgaard/Oeschger’ (D/O) oscillations (millennial‐scale warm‐cold oscillations) and 'Heinrich' events in ice and marine sediment cores, respectively [e.g., Dansgaard et al., 1993; Bond and Lotti, 1995]. These Heinrich events are characterized as huge input of ice‐rafted debris (IRD) and meltwater pulses, documenting episodes of sudden instability and collapse of the current Greenland ice sheets and the Laurentide ice sheet, the latter of which covered northern North America several times during the Pleistocene Epoch.

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confidence: 99%

North Atlantic paleoceanography: The last five million years

Stein

Kanamatsu²,

Alvarez-Zarikian

et al. 2006

EoS Transactions

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“…The FAST modeling was conducted for approximately 1 year (Figure ) and thus did not consider very low frequency (multidecadal) trends in BWT such as have been measured or postulated in previous studies (Fukasawa et al, ; Harris & the IODP Expedition 306 Scientists, ; Johnson et al, ). However, the seabed temperature profile curvature induced by decadal warming should be in the same direction across the study site, unlike what was observed on the Scotian Slope (section 4.3).…”

Section: Resultsmentioning

confidence: 99%

Rethinking the Use of Seabed Sediment Temperature Profiles to Trace Submarine Groundwater Flow

Kurylyk

Irvine

Mohammed

et al. 2018

Water Resources Research

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Submarine groundwater fluxes across the seafloor facilitate important hydrological and biogeochemical exchanges between oceans and seabed sediment, yet few studies have investigated spatially distributed groundwater fluxes in deep‐ocean environments such as continental slopes. Heat has been previously applied as a submarine groundwater tracer using an analytical solution to a heat flow equation assuming steady state conditions and homogeneous thermal conductivity. These assumptions are often violated in shallow seabeds due to ocean bottom temperature changes or sediment property variations. Here heat tracing analysis techniques recently developed for terrestrial settings are applied in concert to examine the influences of groundwater flow, ocean temperature changes, and seabed thermal conductivity variations on deep‐ocean sediment temperature profiles. Temperature observations from the sediment and bottom ocean water on the Scotian Slope off eastern Canada are used to demonstrate how simple thermal methods for tracing groundwater can be employed if more comprehensive techniques indicate that the simplifying assumptions are valid. The spatial distribution of the inferred groundwater fluxes on the slope suggests a downward groundwater flow system with recharge occurring over the upper‐middle slope and discharge on the lower slope. We speculate that the downward groundwater flow inferred on the Scotian Slope is due to density‐driven processes arising from underlying salt domes, in contrast with upward slope systems driven by geothermal convection. Improvements in the design of future submarine hydrogeological studies are proposed for thermal data collection and groundwater flow analysis, including new equations that quantify the minimum detectable flux magnitude for a given sensor accuracy and profile length.

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“…IODP Expeditions 303 and 306 were dedicated to the North Atlantic palaeo-oceanography with drill sites south of the Greenland -Scotland Ridge. However, Expedition 306 also revisited ODP Site 642 at the Vøring Plateau with objectives to (Harris et al 2006): (1) document BWT variations and monitor the downhole diffusion over a 5-year period, (2) study the feasibility of reconstructing BWT change over longer time periods, and (3) relate the findings to longterm climatic trends or to spurious fluctuations in the fluid system. These objectives were addressed by drilling a 171.1 m-deep hole, U1315, fitted with a CORK about 2 km SSE of Hole 642E, and installing a 150 m termistor string and an hourly data logger.…”

Section: Borehole Observatory: Iodp Expedition 306mentioning

confidence: 99%

Chapter 46 Scientific deep-sea drilling in high northern latitudes

Thiede

Eldholm

Myhre

2011

Memoirs

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Some 30 years ago the regional aspects of the plate tectonic history of the Norwegian-Greenland Sea and the eastern Arctic Ocean were unravelled and showed that these ocean basins had opened in early Eocene, 55-56 Ma ago. Drilling by Glomar Challenger in the Norwegian -Greenland Sea during Leg 38 of the Deep Sea Drilling Project confirmed the plate tectonic model and established a marine biostratigraphy framework for the region. The leg set the stage for three subsequent Ocean Drilling Program legs of thematically oriented drilling by the Joides Resolution. Leg 104 drilled a deep acoustic basement hole on the Vøring Plateau, which has become a legacy hole for volcanic margin studies, and provided new key information on the Northern Hemisphere Glaciation and the history of the Norwegian Current. Legs 151 and 162 addressed North Atlantic-Arctic gateways problems. During Leg 151 the Joides Resolution succeeded, with icebreaker support, in reaching the ice-free waters north of Svalbard, thus for the first time bringing a scientific drill ship into the Arctic Ocean. In 2004, the Integrated Ocean Drilling Program organized the mission-specific Expedition 302 to the Lomonosov Ridge in the permanently ice-covered central Arctic Ocean. Comprising a flotilla of three icebreakers, it was a major logistical venture, and resulted in a huge scientific success. The same year the deep site on the Vøring Plateau was revisited and a thermal borehole observatory installed. During these legs a large quantity of core samples has allowed the scientific community to address fundamental questions in terms of continental margin development; plate tectonics; nature of basement; marine biostratigraphy; and the temporal and spatial evolution of the high-latitude northern climate and environments. However, major challenges remain, in particular related to the deep basins, ridges and margins of the Arctic Ocean proper. The next advance in knowledge is contingent on new technology and research infrastructure both for drilling and site surveying. Presently, plans for a new research icebreaker with drilling capability are being developed, the Aurora Borealis project. It will allow systematic drilling in most of the permanently ice-covered basins in the high north. The northern high latitudes have been predicted to contain vast hydrocarbon resources and cooperative ventures between industry and academia may be advantageous.

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Borehole Observatory Installations on IODP Expedition 306 Reconstruct Bottom-Water Temperature Changes in the Norwegian Sea

Cited by 9 publications

References 18 publications

North Atlantic paleoceanography: The last five million years

North Atlantic paleoceanography: The last five million years

Rethinking the Use of Seabed Sediment Temperature Profiles to Trace Submarine Groundwater Flow

Chapter 46 Scientific deep-sea drilling in high northern latitudes

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