A North Pole thermal anomaly? Evidence from new and existing heat flow measurements from the central Arctic Ocean

Shephard, Grace E.; Wiers, Steffen; Bazhenova, E.; Pérez, Lara F.; Mejía, Luz María; Johansson, Carina; O’Regan, Matt

doi:10.1016/j.jog.2018.01.017

Cited by 18 publications

(10 citation statements)

References 72 publications

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“…Since 2000, several shipboard piston coring programs have acquired coincident heat flow data within the Amerasian Basin and on its periphery, producing data that either complement or overlap the geographical coverage of T‐3 data. These data include those collected on the icebreaker Oden on the East Siberian continental slope and the east Lomonosov Ridge (O'Regan et al, ); across Mendeleev Ridge on the Polarstern during ARK‐XXIII/3 (Jokat, ); and for two locations near Alpha Ridge and one in Canada Basin, as well as previously unpublished data that include some sites in the Amerasian Basin (Shephard et al, ). Additional heat flow programs carried out on the Lomonosov Ridge (Xiao et al, ) and Gakkel Ridge (Urlaub et al, ) have increased the number of data for the Eurasian Basin part of the Arctic Ocean, but are not considered further here.…”

Section: Discussionmentioning

confidence: 99%

“…Compiled heat flow measurements for the Amerasian Basin and part of the Eurasian basin, color coded by measured heat flow, with the outline of the HAMH shown by the dashed white curve. T‐3 measurements are depicted as circles, CESAR ice island heat flow (Taylor et al, ) as diamonds, data collected roughly along 81°N (Jokat, ) as triangles, East Siberian margin data (O'Regan et al, ) as asterisks, recent Oden heat flow data and some additional previously unpublished data (Shephard et al, ) as crosses, and other historic heat flow measurements documented in the Global Heat Flow database (IHFC, ) as stars. Not shown is a recent survey of the Lomonosov Ridge by Xiao et al () nor Eurasian basin data from Urlaub et al ().…”

Section: Settingmentioning

confidence: 99%

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Heat Flow in the Western Arctic Ocean (Amerasian Basin)

et al. 2019

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From 1963 to 1973 the U.S. Geological Survey measured heat flow at 356 sites in the Amerasian Basin (Western Arctic Ocean) from a drifting ice island (T‐3). The resulting measurements, which are unevenly distributed on Alpha‐Mendeleev Ridge and in Canada and Nautilus Basins, greatly expand available heat flow data for the Arctic Ocean. Average T‐3 heat flow is ~54.7 ± 11.3 mW/m2, and Nautilus Basin is the only well‐surveyed area (~13% of data) with significantly higher average heat flow (63.8 mW/m2). Heat flow and bathymetry are not correlated at a large scale, and turbiditic surficial sediments (Canada and Nautilus Basins) have higher heat flow than the sediments that blanket the Alpha‐Mendeleev Ridge. Thermal gradients are mostly near‐linear, implying that conductive heat transport dominates and that near‐seafloor sediments are in thermal equilibrium with overlying bottom waters. Combining the heat flow data with modern seismic imagery suggests that some of the observed heat flow variability may be explained by local changes in lithology or the presence of basement faults that channel circulating seawater. A numerical model that incorporates thermal conductivity variations along a profile from Canada Basin (thick sediment on mostly oceanic crust) to Alpha Ridge (thin sediment over thick magmatic units associated with the High Arctic Large Igneous Province) predicts heat flow slightly lower than that observed on Alpha Ridge. This, along with other observations, implies that circulating fluids modulate conductive heat flow and contribute to high variability in the T‐3 data set.

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Section: Discussionmentioning

confidence: 99%

Section: Settingmentioning

confidence: 99%

Heat Flow in the Western Arctic Ocean (Amerasian Basin)

et al. 2019

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“…Unfortunately, no direct measurements of heat flow were obtained at the coring stations during TRANSSIZ 2015 and existing heat flow data from the Yermak Plateau are relatively sparse (Okay and Crane, 1993;Shephard et al, 2018).…”

Section: Paleotemperature and Other Possible Effects 235mentioning

confidence: 99%

“…Existing measurements do indicate that regions of the Yermak Plateau are characterised by relatively high heat flow (>100 mW/m 2 ), but with considerable spatial variability. Most measurements lie in the range of 50 to 100 mW/m 2 (Shephard et al, 2018). If we use a thermal conductivity of 1.17 W/mK, reported from measurements on a core obtained 260 from the Yermak Plateau (Shephard et al, 2018), heat flow of 50-100 m/Wm 2 translates into geothermal gradients of 43 to 85 o C/km (0.043 to 0.085 o C/m).…”

Section: Paleotemperature and Other Possible Effects 235mentioning

confidence: 99%

“…Most measurements lie in the range of 50 to 100 mW/m 2 (Shephard et al, 2018). If we use a thermal conductivity of 1.17 W/mK, reported from measurements on a core obtained 260 from the Yermak Plateau (Shephard et al, 2018), heat flow of 50-100 m/Wm 2 translates into geothermal gradients of 43 to 85 o C/km (0.043 to 0.085 o C/m). At a depth of 6 m below the seafloor, this range of geothermal gradients would amount to a present-day in-situ temperature difference of only 0.25 o C. Thus, it seems unlikely that local heat flow variations would significantly affect rates of racemization at the shallow sediment depth of these samples.…”

Section: Paleotemperature and Other Possible Effects 235mentioning

confidence: 99%

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Amino acid racemization in Quaternary foraminifera from the Yermak Plateau

West¹,

Kaufman²,

Muschitiello³

et al. 2019

Preprint

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Abstract. Amino acid racemization (AAR) geochronology is a powerful tool for dating Quaternary marine sediments across the globe, yet its application to Arctic Ocean sediments has been limited. Anomalous rates of AAR in foraminifera from the central Arctic were reported in previously published studies, indicating that either the rate of racemization is higher in this area, or inaccurate age models were used to constrain the sediment ages. This study investigates racemization rates in foraminifera from three well-dated sediment cores taken from the Yermak Plateau during the 2015 TRANSSIZ Expedition on RV Polarstern. D and L isomers of the amino acids, aspartic acid (Asp) and glutamic acid (Glu), were separated in samples of the planktic foraminifera, Neogloboquadrina pachyderm and the benthic species, Cassidulina neoteretis to quantify the extent of racemization. In total, 241 subsamples were analysed, extending back to Marine Isotope Stage (MIS) 7. Two previously published power functions, which relate the extent of racemization of Asp and Glu in foraminifera to sample age are revisited, and a comparison is made between the ages predicted by these calibrated age equations and independent geochronological constraints available for the cores. Our analyses reveal an excellent match between ages predicted by a global compilation of racemization rates for N. pachyderma, and confirm that a proposed Arctic-specific calibration curve is not applicable at the Yermak Plateau. These results generally support the rates of AAR determined for other cold bottom water sites, and further highlight the anomalous nature of the purportedly high rate of racemization indicated by previous analyses of central Arctic sediments.

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Geodynamics of the Arctic: From proterozoic orogens to present day seafloor spreading

Smelror

Петров

2018

Journal of Geodynamics

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A North Pole thermal anomaly? Evidence from new and existing heat flow measurements from the central Arctic Ocean

Cited by 18 publications

References 72 publications

Heat Flow in the Western Arctic Ocean (Amerasian Basin)

Heat Flow in the Western Arctic Ocean (Amerasian Basin)

Amino acid racemization in Quaternary foraminifera from the Yermak Plateau

Geodynamics of the Arctic: From proterozoic orogens to present day seafloor spreading

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