scholarly journals The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea, a review

2017 ◽  
Author(s):  
Anonymous
Keyword(s):  
Arctic Ocean ◽  
Chukchi Sea ◽  
The Arctic ◽  
The Holocene ◽  
The Arctic Ocean ◽  
Reservoir Age

Supplementary material to "The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea"

2016 ◽  
Author(s):  
Christof Pearce ◽  
Aron Varhelyi ◽  
Stefan Wastegård ◽  
Francesco Muschitiello ◽  
Natalia Barrientos ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Chukchi Sea ◽  
The Arctic ◽  
The Holocene ◽  
The Arctic Ocean ◽  
Supplementary Material ◽  
Reservoir Age

scholarly journals The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

2016 ◽  
Author(s):  
Christof Pearce ◽  
Aron Varhelyi ◽  
Stefan Wastegård ◽  
Francesco Muschitiello ◽  
Natalia Barrientos ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Sediment Core ◽  
Marine Sediment ◽  
Late Holocene ◽  
Volcanic Ash ◽  
Chukchi Sea ◽  
The Arctic ◽  
The Holocene ◽  
The Arctic Ocean ◽  
Reservoir Age

Abstract. The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal ka BP, was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid – late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 72 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed between 550 and 711 cm core depth. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically ''carbon-old'' Pacific waters and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset, is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm/kyr throughout the last 4000 years, and the chronology presented here provides a solid base for high resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea.

scholarly journals The 3.6 ka Aniakchak tephra in the Arctic Ocean: a constraint on the Holocene radiocarbon reservoir age in the Chukchi Sea

2017 ◽  
Vol 13 (4) ◽  
pp. 303-316 ◽  
Author(s):  
Christof Pearce ◽  
Aron Varhelyi ◽  
Stefan Wastegård ◽  
Francesco Muschitiello ◽  
Natalia Barrientos ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Sediment Core ◽  
Marine Sediment ◽  
Late Holocene ◽  
Volcanic Ash ◽  
Chukchi Sea ◽  
The Arctic ◽  
The Holocene ◽  
The Arctic Ocean ◽  
Reservoir Age

Abstract. The caldera-forming eruption of the Aniakchak volcano in the Aleutian Range on the Alaskan Peninsula at 3.6 cal kyr BP was one of the largest Holocene eruptions worldwide. The resulting ash is found as a visible sediment layer in several Alaskan sites and as a cryptotephra on Newfoundland and Greenland. This large geographic distribution, combined with the fact that the eruption is relatively well constrained in time using radiocarbon dating of lake sediments and annual layer counts in ice cores, makes it an excellent stratigraphic marker for dating and correlating mid–late Holocene sediment and paleoclimate records. This study presents the outcome of a targeted search for the Aniakchak tephra in a marine sediment core from the Arctic Ocean, namely Core SWERUS-L2-2-PC1 (2PC), raised from 57 m water depth in Herald Canyon, western Chukchi Sea. High concentrations of tephra shards, with a geochemical signature matching that of Aniakchak ash, were observed across a more than 1.5 m long sediment sequence. Since the primary input of volcanic ash is through atmospheric transport, and assuming that bioturbation can account for mixing up to ca. 10 cm of the marine sediment deposited at the coring site, the broad signal is interpreted as sustained reworking at the sediment source input. The isochron is therefore placed at the base of the sudden increase in tephra concentrations rather than at the maximum concentration. This interpretation of major reworking is strengthened by analysis of grain size distribution which points to ice rafting as an important secondary transport mechanism of volcanic ash. Combined with radiocarbon dates on mollusks in the same sediment core, the volcanic marker is used to calculate a marine radiocarbon reservoir age offset ΔR = 477 ± 60 years. This relatively high value may be explained by the major influence of typically carbon-old Pacific waters, and it agrees well with recent estimates of ΔR along the northwest Alaskan coast, possibly indicating stable oceanographic conditions during the second half of the Holocene. Our use of a volcanic absolute age marker to obtain the marine reservoir age offset is the first of its kind in the Arctic Ocean and provides an important framework for improving chronologies and correlating marine sediment archives in this region. Core 2PC has a high sediment accumulation rate averaging 200 cm kyr−1 throughout the last 4000 years, and the chronology presented here provides a solid base for high-resolution reconstructions of late Holocene climate and ocean variability in the Chukchi Sea.

scholarly journals On the circulation, water mass distribution, and nutrient concentrations of the western Chukchi Sea

Ocean Science ◽  
2022 ◽  
Vol 18 (1) ◽  
pp. 29-49
Author(s):  
Jaclyn Clement Kinney ◽  
Karen M. Assmann ◽  
Wieslaw Maslowski ◽  
Göran Björk ◽  
Martin Jakobsson ◽  
...  
Keyword(s):  
Numerical Modelling ◽  
Arctic Ocean ◽  
Dissolved Inorganic Carbon ◽  
Chukchi Sea ◽  
The Arctic ◽  
Sediment Surface ◽  
Nutrient Concentrations ◽  
Bering Strait ◽  
East Siberian Sea ◽  
The Arctic Ocean

Abstract. Substantial amounts of nutrients and carbon enter the Arctic Ocean from the Pacific Ocean through the Bering Strait, distributed over three main pathways. Water with low salinities and nutrient concentrations takes an eastern route along the Alaskan coast, as Alaskan Coastal Water. A central pathway exhibits intermediate salinity and nutrient concentrations, while the most nutrient-rich water enters the Bering Strait on its western side. Towards the Arctic Ocean, the flow of these water masses is subject to strong topographic steering within the Chukchi Sea with volume transport modulated by the wind field. In this contribution, we use data from several sections crossing Herald Canyon collected in 2008 and 2014 together with numerical modelling to investigate the circulation and transport in the western part of the Chukchi Sea. We find that a substantial fraction of water from the Chukchi Sea enters the East Siberian Sea south of Wrangel Island and circulates in an anticyclonic direction around the island. This water then contributes to the high-nutrient waters of Herald Canyon. The bottom of the canyon has the highest nutrient concentrations, likely as a result of addition from the degradation of organic matter at the sediment surface in the East Siberian Sea. The flux of nutrients (nitrate, phosphate, and silicate) and dissolved inorganic carbon in Bering Summer Water and Winter Water is computed by combining hydrographic and nutrient observations with geostrophic transport referenced to lowered acoustic Doppler current profiler (LADCP) and surface drift data. Even if there are some general similarities between the years, there are differences in both the temperature–salinity and nutrient characteristics. To assess these differences, and also to get a wider temporal and spatial view, numerical modelling results are applied. According to model results, high-frequency variability dominates the flow in Herald Canyon. This leads us to conclude that this region needs to be monitored over a longer time frame to deduce the temporal variability and potential trends.

A perfect bowl-like submesoscale vortex from seismic reflection transect in the Chukchi Sea, Arctic Ocean

2021 ◽  
Author(s):  
Shun Yang ◽  
Haibin Song ◽  
Kun Zhang
Keyword(s):  
Arctic Ocean ◽  
Water Column ◽  
Chukchi Sea ◽  
The Arctic ◽  
Global Ocean ◽  
Physical Oceanography ◽  
Depth Range ◽  
Seismic Line ◽  
The Arctic Ocean ◽  
The Right

<p>The eddies are ubiquitous in the ocean and play an important role in the transportation and redistribution of heat, salt, carbon, nutrients and other materials in the global ocean, thus can regulate global climate and affect the distribution of marine organism. Compared with mesoscale eddies, submesoscale vortices (SVs) have smaller spatial and temporal scales, which impose higher requirements on observation and simulation. The oceanic SVs have a strong vertical velocity, which provides an important supply of nutrients in the upper ocean.</p><p>Many researchers have studied the SVs in the Arctic Ocean by physical oceanography methods (e.g., <em>in-situ </em>measurements and satellite observations). Here, we found a perfect bowl-like SV using a new method named seismic oceanography (SO). SO can use multichannel seismic (MCS) reflection data to produce surprisingly detailed images of water column. Compared with the traditional physical oceanography methods, SO has the advantages of high acquisition efficiency, high lateral resolution (~10 m) and full depth imaging of seawater.</p><p>We used MCS data to image the water column in the in autumn Northeast Chukchi Sea, and captured a perfect bowl-like structure with a depth range of ~200-620m. The structure is almost bilaterally symmetric and has dip angles of 4.8° and 5.5° on the left and on the right, respectively. And it has a horizontal scale of about 12 km at the top and 4.5 km at the bottom, and both the top and bottom of it are near horizontal. The reflections are almost blank in its interior, but are intense and very narrow (~30 m thick) at the lateral boundaries. This indicated that the interior water is homogeneous and quite different from that around it. Fortunately, there is an XBT station near the seismic line and collected almost simultaneously (only one day apart) with the seismic line. The XBT station shows obvious high temperature anomaly over 2°C at the depth of 210-700 m. Therefore, we concluded the structure is a subsurface warm SV, i.e. anticyclonic warm eddy, and may be a submesoscale coherent vortex (SCV). The anomalies from the surrounding water masses indicate that the SV was created at the edge of the Arctic Ocean and then advected here.</p><p>In addition, we used Rossby number (Ro) and Okubo-Weiss (OW) parameter calculated from daily-averaged re-analysis hydrographic data (~3.5 km of grid spacing at 75°N ) from Copernicus Marine Environment Monitoring Service (CMEMS) to analyze the SV. Result shows that the values of the Ro and OW parameter in the area of the SV are both negative. This also suggests that this SV is an anticyclone. This submesoscale anticyclonic vortex may be generated from the friction effect between the warm inflow from the North Pacific and the right wall of Barrow Canyon after passing through the Bering Strait, and then transported to the Northeast of Chukchi Sea by the Beaufort Gyre.</p>

scholarly journals Reconstruction of Holocene oceanographic conditions in the Northeastern Baffin Bay

2020 ◽  
Author(s):  
Katrine Elnegaard Hansen ◽  
Jacques Giraudeau ◽  
Lukas Wacker ◽  
Christof Pearce ◽  
Marit-Solveig Seidenkrantz
Keyword(s):  
Sea Ice ◽  
Arctic Ocean ◽  
Atlantic Water ◽  
The Arctic ◽  
Subsurface Water ◽  
The Holocene ◽  
Baffin Bay ◽  
Nares Strait ◽  
The Arctic Ocean ◽  
Water Conditions

Abstract. The Baffin Bay is a semi-enclosed basin connecting the Arctic Ocean and the western North Atlantic, thus making out a significant pathway for heat exchange. Here we reconstruct the alternating advection of relatively warmer and saline Atlantic waters versus the incursion of colder Arctic water masses entering the Baffin Bay through the multiple gateways in the Canadian Arctic Archipelago and the Nares Strait during the Holocene. We carried out benthic foraminiferal assemblage analyses, X-Ray Fluorescence scanning and radiocarbon dating of a 738  cm long marine sediment core retrieved from the eastern Baffin Bay near Upernavik (Core AMD14-204C; 987m water depth). Results reveal that the eastern Baffin Bay was subjected to several oceanographic changes during the last 9.2 ka BP. Waning deglacial conditions with enhanced meltwater influxes and an extensive sea-ice cover prevailed in the eastern Baffin Bay from 9.2–7.9 ka BP. A transition towards bottom water ameliorations are recorded at 7.9 ka BP by increased advection of Atlantic water masses, encompassing the Holocene Thermal Maximum. A cold period with growing sea-ice cover at 6.7 ka BP interrupts the overall warm subsurface water conditions, promoted by a weaker northward flow of Atlantic waters. The onset of the Neoglaciation at ca. 2.9 ka BP, is marked by an abrupt transition towards a benthic fauna dominated by agglutinated species likely partly explained by a reduction of the influx of Atlantic water, allowing increased influx of the cold, corrosive Baffin Bay Deep Water originating from the Arctic Ocean, to enter the Baffin Bay through the Nares Strait. These cold subsurface water conditions persisted throughout the late Holocene, only interrupted by short-lived warmings superimposed on this cooling trend.

Modelled Stokes drift in the Marginal ice zones of the Arctic Ocean

2020 ◽  
Author(s):  
Jingkai Li
Keyword(s):  
Arctic Ocean ◽  
Chukchi Sea ◽  
Surface Current ◽  
Reanalysis Data ◽  
Stokes Drift ◽  
The Arctic ◽  
Bulk Wave ◽  
Wave Parameters ◽  
The Arctic Ocean ◽  
Ice Floes

<p>The Stokes drift in the marginal ice zones (MIZ) of the Arctic Ocean is modelled by WAVEWATCH III. Applying two viscoelastic and one empirical frequency-dependent wave-ice models, the modelled wave parameters and spectrum are compared with field observations in the Beaufort-Chukchi Sea. Three wave-ice parameterizations show similar abilities to produce the surface Stokes drift estimated from buoy measurements. By using five-year (2015-2019) hindcasted directional spectra of the autumn Arctic, we present and discuss the monthly mean surface Stokes drift (1-10 cm/s), e-folding depth (1-14 m) and vertically integrated transport (0.1-0.4 m2/s) in the marginal ice zones, which are stronger in October than in September. When bulk wave parameters are adopted to estimate the Stokes drift fields, the surface Stokes drift will be underestimated by about 44-59% with mean ice concentration smaller than 60%, and the Stokes e-folding depth will be overestimated by about 1.4 to 5.0 times increasing from the interior to the edge of the ice cover. Since the Stokes drift may be an important component of the total surface current, we compare the modelled surface Stokes drift with the Eulerian current from reanalysis data, which shows that the mean surface Stokes drift is typically about 30% of the Eulerian current over large parts of the MIZ in Arctic Ocean, and is of the same order or even larger in some sea areas of the Chukchi, E. Siberian and Laptev Seas. It indicates that the Stokes drift is necessary to be considered to better model the dynamic processes of the sea ice, especially for the drift of ice floes.</p>

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