Articles | Volume 19, issue 3
https://doi.org/10.5194/os-19-745-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/os-19-745-2023
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
02 Jun 2023
Research article |
| 02 Jun 2023
| 02 Jun 2023
Mixing and air–sea buoyancy fluxes set the time-mean overturning circulation in the subpolar North Atlantic and Nordic Seas
National Oceanography Centre, Southampton, UK
N. Penny Holliday
National Oceanography Centre, Southampton, UK
Sheldon Bacon
National Oceanography Centre, Southampton, UK
Isabela Le Bras
Woods Hole Oceanographic Institute, Woods Hole, Massachusetts, USA
Related authors
Marilena Oltmanns, N. Penny Holliday, James Screen, Ben I. Moat, Simon A. Josey, D. Gwyn Evans, and Sheldon Bacon
Weather Clim. Dynam., 5, 109–132, https://doi.org/10.5194/wcd-5-109-2024, https://doi.org/10.5194/wcd-5-109-2024, 2024
Short summary
Short summary
The melting of land ice and sea ice leads to freshwater input into the ocean. Based on observations, we show that stronger freshwater anomalies in the subpolar North Atlantic in winter are followed by warmer and drier weather over Europe in summer. The identified link indicates an enhanced predictability of European summer weather at least a winter in advance. It further suggests that warmer and drier summers over Europe can become more frequent under increased freshwater fluxes in the future.
Oliver John Tooth, Helen Louise Johnson, Chris Wilson, and Dafydd Gwyn Evans
Ocean Sci., 19, 769–791, https://doi.org/10.5194/os-19-769-2023, https://doi.org/10.5194/os-19-769-2023, 2023
Short summary
Short summary
This study uses the trajectories of water parcels traced within an ocean model simulation to identify the pathways responsible for the seasonal cycle of dense water formation (overturning) in the eastern subpolar North Atlantic. We show that overturning seasonality is due to the fastest water parcels circulating within the eastern basins in less than 8.5 months. Slower pathways set the average strength of overturning in this region since water parcels cannot escape intense wintertime cooling.
Marilena Oltmanns, N. Penny Holliday, James Screen, D. Gwyn Evans, Simon A. Josey, Sheldon Bacon, and Ben I. Moat
Weather Clim. Dynam. Discuss., https://doi.org/10.5194/wcd-2021-79, https://doi.org/10.5194/wcd-2021-79, 2021
Revised manuscript not accepted
Short summary
Short summary
The Arctic is currently warming twice as fast as the global average. This results in enhanced melting and thus freshwater releases into the North Atlantic. Using a combination of observations and models, we show that atmosphere-ocean feedbacks initiated by freshwater releases into the North Atlantic lead to warmer and drier weather over Europe in subsequent summers. The existence of this dynamical link suggests that European summer weather can potentially be predicted months to years in advance.
Marilena Oltmanns, N. Penny Holliday, James Screen, Ben I. Moat, Simon A. Josey, D. Gwyn Evans, and Sheldon Bacon
Weather Clim. Dynam., 5, 109–132, https://doi.org/10.5194/wcd-5-109-2024, https://doi.org/10.5194/wcd-5-109-2024, 2024
Short summary
Short summary
The melting of land ice and sea ice leads to freshwater input into the ocean. Based on observations, we show that stronger freshwater anomalies in the subpolar North Atlantic in winter are followed by warmer and drier weather over Europe in summer. The identified link indicates an enhanced predictability of European summer weather at least a winter in advance. It further suggests that warmer and drier summers over Europe can become more frequent under increased freshwater fluxes in the future.
Oliver John Tooth, Helen Louise Johnson, Chris Wilson, and Dafydd Gwyn Evans
Ocean Sci., 19, 769–791, https://doi.org/10.5194/os-19-769-2023, https://doi.org/10.5194/os-19-769-2023, 2023
Short summary
Short summary
This study uses the trajectories of water parcels traced within an ocean model simulation to identify the pathways responsible for the seasonal cycle of dense water formation (overturning) in the eastern subpolar North Atlantic. We show that overturning seasonality is due to the fastest water parcels circulating within the eastern basins in less than 8.5 months. Slower pathways set the average strength of overturning in this region since water parcels cannot escape intense wintertime cooling.
Alan D. Fox, Patricia Handmann, Christina Schmidt, Neil Fraser, Siren Rühs, Alejandra Sanchez-Franks, Torge Martin, Marilena Oltmanns, Clare Johnson, Willi Rath, N. Penny Holliday, Arne Biastoch, Stuart A. Cunningham, and Igor Yashayaev
Ocean Sci., 18, 1507–1533, https://doi.org/10.5194/os-18-1507-2022, https://doi.org/10.5194/os-18-1507-2022, 2022
Short summary
Short summary
Observations of the eastern subpolar North Atlantic in the 2010s show exceptional freshening and cooling of the upper ocean, peaking in 2016 with the lowest salinities recorded for 120 years. Using results from a high-resolution ocean model, supported by observations, we propose that the leading cause is reduced surface cooling over the preceding decade in the Labrador Sea, leading to increased outflow of less dense water and so to freshening and cooling of the eastern subpolar North Atlantic.
Marilena Oltmanns, N. Penny Holliday, James Screen, D. Gwyn Evans, Simon A. Josey, Sheldon Bacon, and Ben I. Moat
Weather Clim. Dynam. Discuss., https://doi.org/10.5194/wcd-2021-79, https://doi.org/10.5194/wcd-2021-79, 2021
Revised manuscript not accepted
Short summary
Short summary
The Arctic is currently warming twice as fast as the global average. This results in enhanced melting and thus freshwater releases into the North Atlantic. Using a combination of observations and models, we show that atmosphere-ocean feedbacks initiated by freshwater releases into the North Atlantic lead to warmer and drier weather over Europe in subsequent summers. The existence of this dynamical link suggests that European summer weather can potentially be predicted months to years in advance.
Amy Solomon, Céline Heuzé, Benjamin Rabe, Sheldon Bacon, Laurent Bertino, Patrick Heimbach, Jun Inoue, Doroteaciro Iovino, Ruth Mottram, Xiangdong Zhang, Yevgeny Aksenov, Ronan McAdam, An Nguyen, Roshin P. Raj, and Han Tang
Ocean Sci., 17, 1081–1102, https://doi.org/10.5194/os-17-1081-2021, https://doi.org/10.5194/os-17-1081-2021, 2021
Short summary
Short summary
Freshwater in the Arctic Ocean plays a critical role in the global climate system by impacting ocean circulations, stratification, mixing, and emergent regimes. In this review paper we assess how Arctic Ocean freshwater changed in the 2010s relative to the 2000s. Estimates from observations and reanalyses show a qualitative stabilization in the 2010s due to a compensation between a freshening of the Beaufort Gyre and a reduction in freshwater in the Amerasian and Eurasian basins.
Bogi Hansen, Karin Margretha Húsgarð Larsen, Hjálmar Hátún, Steingrímur Jónsson, Sólveig Rósa Ólafsdóttir, Andreas Macrander, William Johns, N. Penny Holliday, and Steffen Malskær Olsen
Ocean Sci. Discuss., https://doi.org/10.5194/os-2021-14, https://doi.org/10.5194/os-2021-14, 2021
Preprint withdrawn
Short summary
Short summary
Compared to other freshwater sources, runoff from Iceland is small and usually flows into the Nordic Seas. Under certain wind conditions, it can, however, flow into the Iceland Basin and this occurred after 2014, when this region had already freshened from other causes. This explains why the surface freshening in this area became so extreme. The local and shallow character of this runoff allows it to have a disproportionate effect on vertical mixing, winter convection, and biological production.
Alexander Forryan, Sheldon Bacon, Takamasa Tsubouchi, Sinhué Torres-Valdés, and Alberto C. Naveira Garabato
The Cryosphere, 13, 2111–2131, https://doi.org/10.5194/tc-13-2111-2019, https://doi.org/10.5194/tc-13-2111-2019, 2019
Short summary
Short summary
We compare control volume and geochemical tracer-based methods of estimating the Arctic Ocean freshwater budget and find both methods in good agreement. Inconsistencies arise from the distinction between
Atlanticand
Pacificwaters in the geochemical calculations. The definition of Pacific waters is particularly problematic due to the non-conservative nature of the nutrients underpinning the definition and the low salinity characterizing waters entering the Arctic through Bering Strait.
Thomas W. K. Armitage, Sheldon Bacon, Andy L. Ridout, Alek A. Petty, Steven Wolbach, and Michel Tsamados
The Cryosphere, 11, 1767–1780, https://doi.org/10.5194/tc-11-1767-2017, https://doi.org/10.5194/tc-11-1767-2017, 2017
Short summary
Short summary
We present a new 12-year record of geostrophic currents at monthly resolution in the ice-covered and ice-free Arctic Ocean and characterise their seasonal to decadal variability. We also present seasonal climatologies of eddy kinetic energy, and examine the changing location of the Beaufort Gyre. Geostrophic current variability highlights the complex interplay between seasonally varying forcing and sea ice conditions, changing ice–ocean coupling and increasing ocean surface stress in the 2000s.
A. J. G. Nurser and S. Bacon
Ocean Sci., 10, 967–975, https://doi.org/10.5194/os-10-967-2014, https://doi.org/10.5194/os-10-967-2014, 2014
Short summary
Short summary
Knowledge of the size of the Rossby radius is important, because it is the horizontal scale of boundary currents, eddies and fronts in fluids on a rotating planet. We find that, in the deep basins of the Arctic Ocean, the Rossby radius is around 10km, but in the shallow shelf seas, it can be less than 1km. This presents a challenge to measurements and models alike.
Related subject area
Approach: In situ Observations | Properties and processes: Overturning circulation | Depth range: All Depths | Geographical range: Deep Seas: North Atlantic | Challenges: Oceans and climate
Observation-based estimates of volume, heat, and freshwater exchanges between the subpolar North Atlantic interior, its boundary currents, and the atmosphere
A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline
Sam C. Jones, Neil J. Fraser, Stuart A. Cunningham, Alan D. Fox, and Mark E. Inall
Ocean Sci., 19, 169–192, https://doi.org/10.5194/os-19-169-2023, https://doi.org/10.5194/os-19-169-2023, 2023
Short summary
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Warm water is transported from the tropical Atlantic towards western Europe and the Arctic. It loses heat to the atmosphere on the way, which strongly influences the climate. We construct a dataset encircling the North Atlantic basin north of 47° N. We calculate how and where heat enters and leaves the basin and how much cooling must happen in the interior. We find that cooling in the north-eastern Atlantic is a crucial step in controlling the conversion of water to higher densities.
Emma L. Worthington, Ben I. Moat, David A. Smeed, Jennifer V. Mecking, Robert Marsh, and Gerard D. McCarthy
Ocean Sci., 17, 285–299, https://doi.org/10.5194/os-17-285-2021, https://doi.org/10.5194/os-17-285-2021, 2021
Short summary
Short summary
The RAPID array has observed the Atlantic meridional overturning circulation (AMOC) since 2004, but the AMOC was directly calculated only five times from 1957–2004. Here we create a statistical regression model from RAPID data, relating AMOC changes to density changes within the different water masses at 26° N, and apply it to historical hydrographic data. The resulting 1981–2016 record shows that the AMOC from 2008–2012 was its weakest since the mid-1980s, but it shows no overall decline.
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Short summary
This study investigates the processes that form dense water in the high latitudes of the North Atlantic to determine how they affect the overturning circulation in the Atlantic. We show for the first time that turbulent mixing is an important driver in the formation of dense water, along with the loss of heat from the ocean to the atmosphere. We point out that the simulation of turbulent mixing in ocean–climate models must improve to better predict the ocean's response to climate change.
This study investigates the processes that form dense water in the high latitudes of the North...
