scholarly journals Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

2017 ◽  
Author(s):  
Masanobu Yamamoto ◽  
Seung-Il Nam ◽  
Leonid Polyak ◽  
Daisuke Kobayashi ◽  
Kenta Suzuki ◽  
...  
Keyword(s):  
Sea Ice ◽  
Chukchi Sea ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Circulation System ◽  
Bering Strait ◽  
The Holocene ◽  
Middle Holocene ◽  
Beaufort Gyre

Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz/feldspar and chlorite/illite ratios in three sediment cores from the northern Chukchi Sea providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz/feldspar ratio, a proxy of the BG strength, gradually decreased during the Holocene, suggesting a long-term decline in the BG strength, consistent with orbitally-controlled decrease in summer insolation. We suppose that the BG rotation weakened as a result of increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing insolation. Millennial to multi-centennial variability in the quartz/feldspar ratio (the BG circulation) is consistent with fluctuations in solar irradiance, suggesting that solar activity affected the BG strength on these timescales. The BSI approximated by the chlorite/illite record shows intensified flow from the Bering Sea to the Arctic during the middle Holocene, which is attributed primarily to the effect of an overall weaker Aleutian Low. The middle Holocene intensification of the BSI was associated with decrease in sea ice concentrations and increase in marine production, as indicated by biomarker concentrations, suggesting an influence of the BSI on sea ice distribution and biological production in the Chukchi Sea.

scholarly journals Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

2017 ◽  
Vol 13 (9) ◽  
pp. 1111-1127 ◽  
Author(s):  
Masanobu Yamamoto ◽  
Seung-Il Nam ◽  
Leonid Polyak ◽  
Daisuke Kobayashi ◽  
Kenta Suzuki ◽  
...  
Keyword(s):  
Solar Activity ◽  
Sea Ice ◽  
Chukchi Sea ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Circulation System ◽  
Bering Strait ◽  
The Holocene ◽  
Beaufort Gyre

Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz ∕ feldspar and chlorite ∕ illite ratios in three sediment cores from the northern Chukchi Sea, providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz ∕ feldspar ratio, interpreted as a proxy of the BG strength, gradually decreased during the Holocene, suggesting a long-term decline in the BG strength, consistent with an orbitally controlled decrease in summer insolation. We propose that the BG rotation weakened as a result of the increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing insolation. Millennial to multi-centennial variability in the quartz ∕ feldspar ratio (the BG circulation) is consistent with fluctuations in solar irradiance, suggesting that solar activity affected the BG strength on these timescales. The BSI approximation by the chlorite ∕ illite record, despite a considerable geographic variability, consistently shows intensified flow from the Bering Sea to the Arctic during the middle Holocene, which is attributed primarily to the effect of higher atmospheric pressure over the Aleutian Basin. The intensified BSI was associated with decrease in sea-ice concentrations and increase in marine production, as indicated by biomarker concentrations, suggesting a major influence of the BSI on sea-ice and biological conditions in the Chukchi Sea. Multi-century to millennial fluctuations, presumably controlled by solar activity, were also identified in a proxy-based BSI record characterized by the highest age resolution.

scholarly journals Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

2016 ◽  
Author(s):  
Masanobu Yamamoto ◽  
Seung Il Nam ◽  
Leonid Polyak ◽  
Daisuke Kobayashi ◽  
Kenta Suzuki ◽  
...  
Keyword(s):  
North Atlantic ◽  
Chukchi Sea ◽  
The Arctic ◽  
Bering Strait ◽  
The Holocene ◽  
The North ◽  
Beaufort Gyre ◽  
The North Atlantic ◽  
Gyre Circulation

Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz/feldspar and chlorite/illite ratios in two sediment cores from the northern Chukchi Sea providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz/feldspar ratio, a proxy of the BG strength, gradually decreased during the Holocene, suggesting a long-term decline in the BG strength, consistent with orbitally-controlled decrease in summer insolation. We suppose that the BG rotation weakened as a result of increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing insolation. Millennial to multi-centennial variability in the quartz/feldspar ratio (the BG circulation) is consistent with fluctuations in solar irradiance, suggesting that solar activity affected the BG strength on these timescales. The BSI, approximated by the chlorite/illite record, shows intensified flow from the Bering Sea to the Arctic during the middle Holocene, which is attributed primarily to the effect of an overall weaker Aleutian Low. This middle Holocene strengthening of the BSI was coeval with intense subpolar gyre circulation in the North Atlantic. We propose that the BSI is linked with the North Atlantic circulation via an atmospheric teleconnection between the Aleutian and Icelandic Lows. A correspondence between the Holocene variability of the BSI and North Atlantic Drift suggests that this connection is involved in a mechanism muting salinity changes in the North Atlantic, and thereby stabilizing the Atlantic Meridional Overturning Circulation.

scholarly journals On the Link between Arctic Sea Ice Decline and the Freshwater Content of the Beaufort Gyre: Insights from a Simple Process Model

2014 ◽  
Vol 27 (21) ◽  
pp. 8170-8184 ◽  
Author(s):  
Peter E. D. Davis ◽  
Camille Lique ◽  
Helen L. Johnson
Keyword(s):  
Sea Ice ◽  
Momentum Transfer ◽  
Momentum Flux ◽  
Process Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Simple Process ◽  
Beaufort Gyre ◽  
Arctic Sea ◽  
The Arctic Ocean

Abstract Recent satellite and hydrographic observations have shown that the rate of freshwater accumulation in the Beaufort Gyre of the Arctic Ocean has accelerated over the past decade. This acceleration has coincided with the dramatic decline observed in Arctic sea ice cover, which is expected to modify the efficiency of momentum transfer into the upper ocean. Here, a simple process model is used to investigate the dynamical response of the Beaufort Gyre to the changing efficiency of momentum transfer, and its link with the enhanced accumulation of freshwater. A linear relationship is found between the annual mean momentum flux and the amount of freshwater accumulated in the Beaufort Gyre. In the model, both the response time scale and the total quantity of freshwater accumulated are determined by a balance between Ekman pumping and an eddy-induced volume flux toward the boundary, highlighting the importance of eddies in the adjustment of the Arctic Ocean to a change in forcing. When the seasonal cycle in the efficiency of momentum transfer is modified (but the annual mean momentum flux is held constant), it has no effect on the accumulation of freshwater, although it does impact the timing and amplitude of the annual cycle in Beaufort Gyre freshwater content. This suggests that the decline in Arctic sea ice cover may have an impact on the magnitude and seasonality of the freshwater export into the North Atlantic.

scholarly journals Mid-Holocene Northern Hemisphere warming driven by Arctic amplification

2019 ◽  
Vol 5 (12) ◽  
pp. eaax8203 ◽  
Author(s):  
Hyo-Seok Park ◽  
Seong-Joong Kim ◽  
Andrew L. Stewart ◽  
Seok-Woo Son ◽  
Kyong-Hwan Seo
Keyword(s):  
Sea Ice ◽  
Northern Hemisphere ◽  
High Latitude ◽  
Climate Model ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Amplification ◽  
The Holocene ◽  
Holocene Thermal Maximum ◽  
Thermal Maximum

The Holocene thermal maximum was characterized by strong summer solar heating that substantially increased the summertime temperature relative to preindustrial climate. However, the summer warming was compensated by weaker winter insolation, and the annual mean temperature of the Holocene thermal maximum remains ambiguous. Using multimodel mid-Holocene simulations, we show that the annual mean Northern Hemisphere temperature is strongly correlated with the degree of Arctic amplification and sea ice loss. Additional model experiments show that the summer Arctic sea ice loss persists into winter and increases the mid- and high-latitude temperatures. These results are evaluated against four proxy datasets to verify that the annual mean northern high-latitude temperature during the mid-Holocene was warmer than the preindustrial climate, because of the seasonally rectified temperature increase driven by the Arctic amplification. This study offers a resolution to the “Holocene temperature conundrum”, a well-known discrepancy between paleo-proxies and climate model simulations of Holocene thermal maximum.

Cascading and the pathways of the key biogeochemical tracers in the Canadian Basin: from models and observations.

2020 ◽  
Author(s):  
Maria Luneva ◽  
Yevgeny Aksenov ◽  
Vladimir Ivanov ◽  
Stephen Kelly ◽  
Fedor Tuzov
Keyword(s):  
Chukchi Sea ◽  
Gravity Current ◽  
The Arctic ◽  
Bering Strait ◽  
Low Salinity ◽  
Beaufort Gyre ◽  
Pacific Waters ◽  
Brine Rejection ◽  
Ice Model

<p>We explore dense water cascading (DWC; a type of bottom-trapped gravity current) on multi-decadal time scales using a pan-Arctic regional ocean-ice model. DWC is particularly important in the Arctic Ocean as the main mechanism of ventilation of interior waters when open ocean convection is blocked by strong density stratification. We identify the locations where the most intense DWC events occur and evaluate the associated cross-shelf mass, heat and salt fluxes. </p><p> </p><p>A detailed analysis of specific cascading sites around the Beaufort Gyre and adjacent regions is performed. We find that autumn upwelling of warm and saltier Atlantic waters on the shelf and subsequent cooling and mixing of uplifted waters trigger the cascading on the West Chukchi Sea shelf break. We also perform Lagragian particle tacking of low salinity Pacific waters originating at the surface in the Bering Strait; these waters are shown to be modified by brine rejection and cooling, and through subsequent mixing become dense enough to reach depths of 160-200m and below. We examine the role of cascading and shelf upwelling on the shelf waters transformation, pathways and spread of the biological important tracers (O18, Si., DIC snd DIN).</p>

scholarly journals Inter-comparison of snow depth retrievals over Arctic sea ice from radar data acquired by Operation IceBridge

2017 ◽  
Author(s):  
Ron Kwok ◽  
Nathan T. Kurtz ◽  
Ludovic Brucker ◽  
Alvaro Ivanoff ◽  
Thomas Newman ◽  
...  
Keyword(s):  
Sea Ice ◽  
Data Quality ◽  
Snow Depth ◽  
Radar Data ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Retrieval Algorithms ◽  
Snow Thickness

Abstract. Since 2009, the ultra-wideband snow-radar on Operation IceBridge has acquired data in annual campaigns conducted during the Arctic and Antarctic springs. Progressive improvements in radar hardware and data processing methodologies have led to improved data quality for subsequent retrieval of snow depth. Existing retrieval algorithms differ in the way the air-snow and snow-ice interfaces are detected and localized in the radar returns, and in how the system limitations are addressed (e.g., noise, resolution). In 2014, the Snow Thickness On Sea Ice Working Group (STOSIWG) was formed and tasked with investigating how radar data quality affect snow depth retrievals and how retrievals from the various algorithms differ. The goal is to understand the limitations of the estimates and to produce a well-documented, long-term record that can be used for understanding broader changes in the Arctic climate system. Here, we assess five retrieval algorithms by comparisons with field measurements from two ground-based campaigns, including the BRomine Ozone Mercury EXperiment (BROMEX) at Barrow, Alaska and a field program by Environment and Climate Change Canada (ECCC) at Eureka, Nunavut, available climatology and snowfall from ERA-Interim reanalysis. The aim is to examine available algorithms and to use the assessment results to inform the development of future approaches. We present results from these assessments and highlight key considerations for the production of a long-term, calibrated geophysical record of springtime snow thickness over Arctic sea ice.

scholarly journals Exploring the utility of quantitative network design in evaluating Arctic sea-ice thickness sampling strategies

2015 ◽  
Vol 9 (2) ◽  
pp. 1735-1768 ◽  
Author(s):  
T. Kaminski ◽  
F. Kauker ◽  
H. Eicken ◽  
M. Karcher
Keyword(s):  
Sea Ice ◽  
Network Design ◽  
Chukchi Sea ◽  
Software Tool ◽  
Severity Index ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Target Area ◽  
Sea Ice Thickness ◽  
Arctic Sea

Abstract. We present a quantitative network design (QND) study of the Arctic sea ice-ocean system using a software tool that can evaluate hypothetical observational networks in a variational data assimilation system. For a demonstration, we evaluate two idealised flight transects derived from NASA's Operation IceBridge airborne ice surveys in terms of their potential to improve ten-day to five-month sea-ice forecasts. As target regions for the forecasts we select the Chukchi Sea, an area particularly relevant for maritime traffic and offshore resource exploration, as well as two areas related to the Barnett Ice Severity Index (BSI), a standard measure of shipping conditions along the Alaskan coast that is routinely issued by ice services. Our analysis quantifies the benefits of sampling upstream of the target area and of reducing the sampling uncertainty. We demonstrate how observations of sea-ice and snow thickness can constrain ice and snow variables in a target region and quantify the complementarity of combining two flight transects. We further quantify the benefit of improved atmospheric forecasts and a well-calibrated model.

scholarly journals Exploring the utility of quantitative network design in evaluating Arctic sea ice thickness sampling strategies

2015 ◽  
Vol 9 (4) ◽  
pp. 1721-1733 ◽  
Author(s):  
T. Kaminski ◽  
F. Kauker ◽  
H. Eicken ◽  
M. Karcher
Keyword(s):  
Sea Ice ◽  
Network Design ◽  
Chukchi Sea ◽  
Software Tool ◽  
Severity Index ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Target Area ◽  
Sea Ice Thickness ◽  
Arctic Sea

Abstract. We present a quantitative network design (QND) study of the Arctic sea ice–ocean system using a software tool that can evaluate hypothetical observational networks in a variational data assimilation system. For a demonstration, we evaluate two idealised flight transects derived from NASA's Operation IceBridge airborne ice surveys in terms of their potential to improve 10-day to 5-month sea ice forecasts. As target regions for the forecasts we select the Chukchi Sea, an area particularly relevant for maritime traffic and offshore resource exploration, as well as two areas related to the Barnett ice severity index (BSI), a standard measure of shipping conditions along the Alaskan coast that is routinely issued by ice services. Our analysis quantifies the benefits of sampling upstream of the target area and of reducing the sampling uncertainty. We demonstrate how observations of sea ice and snow thickness can constrain ice and snow variables in a target region and quantify the complementarity of combining two flight transects. We further quantify the benefit of improved atmospheric forecasts and a well-calibrated model.

scholarly journals Intercomparison of snow depth retrievals over Arctic sea ice from radar data acquired by Operation IceBridge

2017 ◽  
Vol 11 (6) ◽  
pp. 2571-2593 ◽  
Author(s):  
Ron Kwok ◽  
Nathan T. Kurtz ◽  
Ludovic Brucker ◽  
Alvaro Ivanoff ◽  
Thomas Newman ◽  
...  
Keyword(s):  
Sea Ice ◽  
Data Quality ◽  
Snow Depth ◽  
Radar Data ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Arctic Sea ◽  
Retrieval Algorithms ◽  
Snow Thickness

Abstract. Since 2009, the ultra-wideband snow radar on Operation IceBridge (OIB; a NASA airborne mission to survey the polar ice covers) has acquired data in annual campaigns conducted during the Arctic and Antarctic springs. Progressive improvements in radar hardware and data processing methodologies have led to improved data quality for subsequent retrieval of snow depth. Existing retrieval algorithms differ in the way the air–snow (a–s) and snow–ice (s–i) interfaces are detected and localized in the radar returns and in how the system limitations are addressed (e.g., noise, resolution). In 2014, the Snow Thickness On Sea Ice Working Group (STOSIWG) was formed and tasked with investigating how radar data quality affects snow depth retrievals and how retrievals from the various algorithms differ. The goal is to understand the limitations of the estimates and to produce a well-documented, long-term record that can be used for understanding broader changes in the Arctic climate system. Here, we assess five retrieval algorithms by comparisons with field measurements from two ground-based campaigns, including the BRomine, Ozone, and Mercury EXperiment (BROMEX) at Barrow, Alaska; a field program by Environment and Climate Change Canada at Eureka, Nunavut; and available climatology and snowfall from ERA-Interim reanalysis. The aim is to examine available algorithms and to use the assessment results to inform the development of future approaches. We present results from these assessments and highlight key considerations for the production of a long-term, calibrated geophysical record of springtime snow thickness over Arctic sea ice.

The impact of denying sea ice information on the predictability of atmospheric processes over the Arctic and at mid-latitude regions

2020 ◽  
Author(s):  
Leandro Ponsoni ◽  
Daniela Flocco ◽  
François Massonnet ◽  
Steve Delhaye ◽  
Ed Hawkins ◽  
...  
Keyword(s):  
Sea Ice ◽  
General Circulation ◽  
Model Comparison ◽  
General Circulation Models ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Atmospheric Processes ◽  
Ice Conditions ◽  
The Impact

<p>In this work, we make use of an inter-model comparison and of a perfect model approach, in which model outputs are used as true reference states, to assess the impact that denying sea ice information has on the prediction of atmospheric processes, both over the Arctic and at mid-latitude regions. To do so, two long-term control runs (longer than 250 years) were generated with two state-of-the-art General Circulation Models (GCM), namely EC-Earth and HadGEM. From these two reference states, we have identified three different years in which the Arctic sea ice volume (SIV) was (i) maximum, (ii) minimum and (iii) a representative case for the mean state. By departing from each of these three dates (not necessarily the same for the two models), we generated a set of experiments in which the control runs are restarted both from original and climatological sea ice conditions. Here, climatological sea ice conditions are estimated as the time-average of sea ice parameters from the respective long-term control runs. The experiments are 1-year long and all of them start in January when ice is still thin, snow depth is small, air-ocean temperatures contrast the most and, therefore, the heat conductive flux in sea ice (at the surface) is nearly maximum. To robustly separate the response to degrading the initial sea ice state from background internal variability, each of the two counterfactual experiments (reference and climatological) consists of 50 ensembles members. Threstatedese ensembles are generated by adding small random perturbations to the sea surface temperature (EC-Earth) or to the air temperature (HadGEM) fields. Preliminary results reinforce the importance of having the right sea ice state for improving the (sub-)seasonal prediction of atmospheric parameters (e.g., 2m-temperature and geopotential) and circulation (e.g., Westerlies and Jet Stream) not only over the Arctic, but also at mid-latitude regions.</p>

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