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Article ; Online: Significant variability of structure and predictability of Arctic Ocean surface pathways affects basin-wide connectivity

Chris Wilson / Yevgeny Aksenov / Stefanie Rynders / Stephen J. Kelly / Thomas Krumpen / Andrew C. Coward

Communications Earth & Environment, Vol 2, Iss 1, Pp 1-

2021 Volume 10

Abstract: The Transpolar Drift, which governs the transport of freshwater, nutrients, carbon and contaminants across the Arctic Ocean, varies interannually, and is affected by fine-scale flow structures and processes, according to high-resolution simulations and ... ...

Abstract	The Transpolar Drift, which governs the transport of freshwater, nutrients, carbon and contaminants across the Arctic Ocean, varies interannually, and is affected by fine-scale flow structures and processes, according to high-resolution simulations and satellite data.
Keywords	Geology ; QE1-996.5 ; Environmental sciences ; GE1-350
Language	English
Publishing date	2021-08-01T00:00:00Z
Publisher	Nature Portfolio
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Improved Arctic Sea Ice Freeboard Retrieval From Satellite Altimetry Using Optimized Sea Surface Decorrelation Scales

Landy, Jack C. / Bouffard, Jerome / Wilson, Chris / Rynders, Stefanie / Aksenov, Yevgeny / Tsamados, Michel

Journal of geophysical research. 2021 Dec., v. 126, no. 12

2021

Abstract: A growing number of studies are concluding that the resilience of the Arctic sea ice cover in a warming climate is essentially controlled by its thickness. Satellite radar and laser altimeters have allowed us to routinely monitor sea ice thickness across ...

Abstract	A growing number of studies are concluding that the resilience of the Arctic sea ice cover in a warming climate is essentially controlled by its thickness. Satellite radar and laser altimeters have allowed us to routinely monitor sea ice thickness across most of the Arctic Ocean for several decades. However, a key uncertainty remaining in the sea ice thickness retrieval is the error on the sea surface height (SSH) which is conventionally interpolated at ice floes from a limited number of lead observations along the altimeter's orbital track. Here, we use an objective mapping approach to determine sea surface height from all proximal lead samples located on the orbital track and from adjacent tracks within a neighborhood of 30–220 (mean 105) km. The patterns of the SSH signal's zonal, meridional, and temporal decorrelation length scales are obtained by analyzing the covariance of historic CryoSat‐2 Arctic lead observations, which match the scales obtained from an equivalent analysis of high‐resolution sea ice‐ocean model fields. We use these length scales to determine an optimal SSH and error estimate for each sea ice floe location. By exploiting leads from adjacent tracks, we can increase the sea ice radar freeboard precision estimated at orbital crossovers by up to 20%. In regions of high SSH uncertainty, biases in CryoSat‐2 radar freeboard can be reduced by 25% with respect to coincident airborne validation data. The new method is not restricted to a particular sensor or mode, so it can be generalized to all present and historic polar altimetry missions.
Keywords	altimeters ; climate ; covariance ; geophysics ; ice cover ; lead ; radar ; research ; satellite altimetry ; satellites ; sea ice ; uncertainty ; Arctic Ocean ; Arctic region
Language	English
Dates of publication	2021-12
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	161667-5
ISSN	2169-9291 ; 2169-9275 ; 0148-0227 ; 0196-2256
ISSN (online)	2169-9291
ISSN	2169-9275 ; 0148-0227 ; 0196-2256
DOI	10.1029/2021JC017466
Database	NAL-Catalogue (AGRICOLA)

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Article ; Online: A year-round satellite sea-ice thickness record from CryoSat-2.

Landy, Jack C / Dawson, Geoffrey J / Tsamados, Michel / Bushuk, Mitchell / Stroeve, Julienne C / Howell, Stephen E L / Krumpen, Thomas / Babb, David G / Komarov, Alexander S / Heorton, Harry D B S / Belter, H Jakob / Aksenov, Yevgeny

Nature

2022 Volume 609, Issue 7927, Page(s) 517–522

Abstract: Arctic sea ice is diminishing with climate ... ...

Abstract	Arctic sea ice is diminishing with climate warming
Language	English
Publishing date	2022-09-14
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	120714-3
ISSN	1476-4687 ; 0028-0836
ISSN (online)	1476-4687
ISSN	0028-0836
DOI	10.1038/s41586-022-05058-5
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Arctic mass, freshwater and heat fluxes: methods and modelled seasonal variability.

Bacon, Sheldon / Aksenov, Yevgeny / Fawcett, Stephen / Madec, Gurvan

Philosophical transactions. Series A, Mathematical, physical, and engineering sciences

2015 Volume 373, Issue 2052

Abstract: Considering the Arctic Ocean (including sea ice) as a defined volume, we develop equations describing the time-varying fluxes of mass, heat and freshwater (FW) into, and storage of those quantities within, that volume. The seasonal cycles of fluxes and ... ...

Abstract	Considering the Arctic Ocean (including sea ice) as a defined volume, we develop equations describing the time-varying fluxes of mass, heat and freshwater (FW) into, and storage of those quantities within, that volume. The seasonal cycles of fluxes and storage of mass, heat and FW are quantified and illustrated using output from a numerical model. The meanings of 'reference values' and FW fluxes are discussed, and the potential for error through the use of arbitrary reference values is examined.
Language	English
Publishing date	2015-10-13
Publishing country	England
Document type	Journal Article
ZDB-ID	208381-4
ISSN	1471-2962 ; 0080-4614 ; 0264-3820 ; 0264-3952 ; 1364-503X
ISSN (online)	1471-2962
ISSN	0080-4614 ; 0264-3820 ; 0264-3952 ; 1364-503X
DOI	10.1098/rsta.2014.0169
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Overview of the MOSAiC expedition

Rabe, Benjamin / Heuzé, Céline / Regnery, Julia / Aksenov, Yevgeny / Allerholt, Jacob / Athanase, Marylou / Bai, Youcheng / Basque, Chris / Bauch, Dorothea / Laukert, Georgi

Physical oceanography

2022

Abstract: Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the ... ...

Abstract	Arctic Ocean properties and processes are highly relevant to the regional and global coupled climate system, yet still scarcely observed, especially in winter. Team OCEAN conducted a full year of physical oceanography observations as part of the Multidisciplinary drifting Observatory for the Study of the Arctic Climate (MOSAiC), a drift with the Arctic sea ice from October 2019 to September 2020. An international team designed and implemented the program to characterize the Arctic Ocean system in unprecedented detail, from the seafloor to the air-sea ice-ocean interface, from sub-mesoscales to pan-Arctic. The oceanographic measurements were coordinated with the other teams to explore the ocean physics and linkages to the climate and ecosystem. This paper introduces the major components of the physical oceanography program and complements the other team overviews of the MOSAiC observational program. Team OCEAN’s sampling strategy was designed around hydrographic ship-, ice- and autonomous platform-based measurements to improve the understanding of regional circulation and mixing processes. Measurements were carried out both routinely, with a regular schedule, and in response to storms or opening leads. Here we present along-drift time series of hydrographic properties, allowing insights into the seasonal and regional evolution of the water column from winter in the Laptev Sea to early summer in Fram Strait: freshening of the surface, deepening of the mixed layer, increase in temperature and salinity of the Atlantic Water. We also highlight the presence of Canada Basin deep water intrusions and a surface meltwater layer in leads. MOSAiC most likely was the most comprehensive program ever conducted over the ice-covered Arctic Ocean. While data analysis and interpretation are ongoing, the acquired datasets will support a wide range of physical oceanography and multi-disciplinary research. They will provide a significant foundation for assessing and advancing modeling capabilities in the Arctic Ocean.
Subject code	551
Language	English
Publishing date	2022-02-07
Publisher	UCP (University of California Press)
Publishing country	de
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Sea ice floe size

Bateson, Adam William / Feltham, Daniel L. / Schröder, David / Wang, Yanan / Hwang, Byongjun / Ridley, Jeff K. / Aksenov, Yevgeny

eISSN: 1994-0424

its impact on pan-Arctic and local ice mass and required model complexity

2022

Abstract: Sea ice is composed of discrete units called floes. Observations show that these floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. Floe size impacts the nature and magnitude of interactions between the sea ... ...

Abstract	Sea ice is composed of discrete units called floes. Observations show that these floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. Floe size impacts the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate and momentum and heat exchange. However, large-scale geophysical sea ice models employ a continuum approach and traditionally either assume floes adopt a constant size or do not include an explicit treatment of floe size. In this study we apply novel observations to analyse two alternative approaches to modelling a floe size distribution (FSD) within the state-of-the-art CICE sea ice model. The first model considered is a prognostic floe size–thickness distribution where the shape of the distribution is an emergent feature of the model and is not assumed a priori. The second model considered, the WIPoFSD (Waves-in-Ice module and Power law Floe Size Distribution) model, assumes floe size follows a power law with a constant exponent. We introduce a parameterisation motivated by idealised models of in-plane brittle fracture to the prognostic model and demonstrate that the inclusion of this scheme enables the prognostic model to achieve a reasonable match against the novel observations for mid-sized floes (100 m–2 km). While neither FSD model results in a significant improvement in the ability of CICE to simulate pan-Arctic metrics in a stand-alone sea ice configuration, larger impacts can be seen over regional scales in sea ice concentration and thickness. We find that the prognostic model particularly enhances sea ice melt in the early melt season, whereas for the WIPoFSD model this melt increase occurs primarily during the late melt season. We then show that these differences between the two FSD models can be explained by considering the effective floe size, a metric used to characterise a given FSD. Finally, we discuss the advantages and disadvantages to these different approaches to modelling the FSD. We ...
Subject code	551
Language	English
Publishing date	2022-06-28
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: The Pension Funds’ Investment Regulation at the Beginning of the 21st Century

Liudmila Lebedeva / Pavel Aksenov / Sergei Yemelyanov / Yevgeny Yemelyanov

Mediterranean Journal of Social Sciences, Vol 6, Iss

Comparative Analysis of Approaches of the USA, Canada, and the EU-15 Countries

2015 Volume 4

Abstract: The article considers the main trends in the EU-15 countries, the USA, and Canada with regard to the current approaches to the pension funds’ investment activities regulation. This countries’ choice is caused by the relevant static information ... ...

Abstract	The article considers the main trends in the EU-15 countries, the USA, and Canada with regard to the current approaches to the pension funds’ investment activities regulation. This countries’ choice is caused by the relevant static information availability, as well as by the private pension funds’ growing role in this group and the diversity of the investment activity funds forms. The difference between the growth rate of the average pension funds and the GDP in a certain country has the special attention because the leading indicators of the funds volume growth, attracted by the pension systems compared with the economy growth as a whole, determine the possibility of higher payments to pensioners and also allows to increase the pension plans coverage of other population groups. The article deals with the legal aspects of the pension funds regulation with respect to their investment strategies, and contains a comparative analysis between the countries. DOI:10.5901/mjss.2015.v6n4s4p155
Keywords	Social Sciences ; H
Subject code	336
Language	English
Publishing date	2015-08-01T00:00:00Z
Publisher	richtmann publishing
Document type	Article ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article: Hotspots of Dense Water Cascading in the Arctic Ocean: Implications for the Pacific Water Pathways

Luneva, Maria V. / Ivanov, Vladimir V. / Tuzov, Fedor / Aksenov, Yevgeny / Harle, James D. / Kelly, Stephen / Holt, Jason T.

Journal of geophysical research. 2020 Oct., v. 125, no. 10

2020

Abstract: We explore dense water cascading (DWC), a type of bottom‐trapped gravity current, on multidecadal 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 ... ...

Abstract	We explore dense water cascading (DWC), a type of bottom‐trapped gravity current, on multidecadal 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. We find that the modeled locations of cascading agree well with the sparse historical observations and that cascading is the dominant process responsible for cross‐shelf exchange in the boundary layers. Simulated DWC fluxes of 1.3 Sv (1 Sv = 10⁶ m³/s) in the Central Arctic are comparable to Bering Strait inflow, with associated surface and benthic Ekman fluxes of 0.85 and 0.58 Sv. With ice decline, both surface Ekman flux and DWC fluxes are increasing at a rate of 0.023 and 0.0175 Sv/year, respectively. A detailed analysis of specific cascading sites around the Beaufort Gyre and adjacent regions shows 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. Lagrangian particle tracking of low salinity Pacific waters originating at the surface in the Bering Strait shows that these waters are modified by brine rejection and cooling, and through subsequent mixing become dense enough to reach depths of 160–200 m.
Keywords	autumn ; convection ; cooling ; decline ; geophysics ; gravity ; ice ; models ; research ; salinity ; Arctic Ocean ; Arctic region ; Chukchi Sea
Language	English
Dates of publication	2020-10
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	161667-5
ISSN	2169-9291 ; 2169-9275 ; 0148-0227 ; 0196-2256
ISSN (online)	2169-9291
ISSN	2169-9275 ; 0148-0227 ; 0196-2256
DOI	10.1029/2020JC016044
Database	NAL-Catalogue (AGRICOLA)

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Book ; Online: Impact of sea ice floe size distribution on seasonal fragmentation and melt of Arctic sea ice

Bateson, Adam W. / Feltham, Daniel L. / Schröder, David / Hosekova, Lucia / Ridley, Jeff K. / Aksenov, Yevgeny

eISSN: 1994-0424

2020

Abstract: Recent years have seen a rapid reduction in the summer Arctic sea ice extent. To both understand this trend and project the future evolution of the summer Arctic sea ice, a better understanding of the physical processes that drive the seasonal loss of ... ...

Abstract	Recent years have seen a rapid reduction in the summer Arctic sea ice extent. To both understand this trend and project the future evolution of the summer Arctic sea ice, a better understanding of the physical processes that drive the seasonal loss of sea ice is required. The marginal ice zone, here defined as regions with between 15 % and 80 % sea ice cover, is the region separating pack ice from the open ocean. Accurate modelling of this region is important to understand the dominant mechanisms involved in seasonal sea ice loss. Evolution of the marginal ice zone is determined by complex interactions between the atmosphere, sea ice, ocean, and ocean surface waves. Therefore, this region presents a significant modelling challenge. Sea ice floes span a range of sizes but sea ice models within climate models assume they adopt a constant size. Floe size influences the lateral melt rate of sea ice and momentum transfer between atmosphere, sea ice, and ocean, all important processes within the marginal ice zone. In this study, the floe size distribution is represented as a power law defined by an upper floe size cut-off, lower floe size cut-off, and power-law exponent. This distribution is also defined by a new tracer that varies in response to lateral melting, wave-induced break-up, freezing conditions, and advection. This distribution is implemented within a sea ice model coupled to a prognostic ocean mixed-layer model. We present results to show that the use of a power-law floe size distribution has a spatially and temporally dependent impact on the sea ice, in particular increasing the role of the marginal ice zone in seasonal sea ice loss. This feature is important in correcting existing biases within sea ice models. In addition, we show a much stronger model sensitivity to floe size distribution parameters than other parameters used to calculate lateral melt, justifying the focus on floe size distribution in model development. We also find that the attenuation rate of waves propagating under the sea ice cover modulates the impact of wave break-up on the floe size distribution. It is finally concluded that the model approach presented here is a flexible tool for assessing the importance of a floe size distribution in the evolution of sea ice and is a useful stepping stone for future development of floe size modelling.
Subject code	290 ; 551
Language	English
Publishing date	2020-02-04
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Book ; Online: Sea ice floe size

Bateson, Adam William / Feltham, Daniel L. / Schröder, David / Wang, Yanan / Hwang, Byongjun / Ridley, Jeff K. / Aksenov, Yevgeny

eISSN: 1994-0424

its impact on pan-Arctic and local ice mass, and required model complexity

2021

Abstract: Sea ice is composed of discrete units called floes. The size of these floes can determine the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate, momentum and heat exchange, and surface moisture ... ...

Abstract	Sea ice is composed of discrete units called floes. The size of these floes can determine the nature and magnitude of interactions between the sea ice, ocean, and atmosphere including lateral melt rate, momentum and heat exchange, and surface moisture flux. Large-scale geophysical sea ice models employ a continuum approach and traditionally either assume floes adopt a constant size or do not include an explicit treatment of floe size. Observations show that floes can adopt a range of sizes spanning orders of magnitude, from metres to tens of kilometres. In this study we apply novel observations to analyse two alternative approaches to modelling a floe size distribution (FSD) within the state-of-the-art CICE sea ice model. The first model considered, the WIPoFSD (Waves-in-Ice module and Power law Floe Size Distribution) model, assumes floe size follows a power law with a constant exponent. The second is a prognostic floe size-thickness distribution where the shape of the distribution is an emergent feature of the model and is not assumed a priori. We demonstrate that a parameterisation of in-plane brittle fracture processes should be included in the prognostic model. While neither FSD model results in a significant improvement in the ability of CICE to simulate pan-Arctic metrics in a stand-alone sea ice configuration, larger impacts can be seen over regional scales in sea ice concentration and thickness. We find that the prognostic model particularly enhances sea ice melt in the early melt season, whereas for the WIPoFSD model this melt increase occurs primarily during the late melt season. We then show that these differences between the two FSD models can be explained by considering the effective floe size, a metric used to characterise a given FSD. Finally, we discuss the advantages and disadvantages to these different approaches to modelling the FSD. We note that the WIPoFSD model is less computationally expensive than the prognostic model and produces a better fit to novel FSD observations derived from 2-m resolution MEDEA imagery but is unable to represent potentially important features of annual FSD evolution seen with the prognostic model.
Subject code	551
Language	English
Publishing date	2021-09-08
Publishing country	de
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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