Articles | Volume 17, issue 1
https://doi.org/10.5194/os-17-285-2021
© Author(s) 2021. 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-17-285-2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Research article
| 
15 Feb 2021
Research article |
| 15 Feb 2021
| 15 Feb 2021
A 30-year reconstruction of the Atlantic meridional overturning circulation shows no decline
Emma L. Worthington
CORRESPONDING AUTHOR
University of Southampton, European Way, Southampton, SO14 3ZH, UK
Ben I. Moat
National Oceanography Centre, European Way, Southampton, SO14 3ZH, UK
David A. Smeed
National Oceanography Centre, European Way, Southampton, SO14 3ZH, UK
Jennifer V. Mecking
National Oceanography Centre, European Way, Southampton, SO14 3ZH, UK
Robert Marsh
University of Southampton, European Way, Southampton, SO14 3ZH, UK
Gerard D. McCarthy
ICARUS, Department of Geography, Maynooth University, Maynooth, Co. Kildare, Ireland
Related authors
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Melissa Wood, Ivan D. Haigh, Quan Quan Le, Hung Nghia Nguyen, Hoang Ba Tran, Stephen E. Darby, Robert Marsh, Nikolaos Skliris, and Joël J.-M. Hirschi
Nat. Hazards Earth Syst. Sci., 24, 3627–3649, https://doi.org/10.5194/nhess-24-3627-2024, https://doi.org/10.5194/nhess-24-3627-2024, 2024
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We look at how compound flooding from the combination of river flooding and storm tides (storm surge and astronomical tide) may be changing over time due to climate change, with a case study of the Mekong River delta. We found that future compound flooding has the potential to flood the region more extensively and be longer lasting than compound floods today. This is useful to know because it means managers of deltas such as the Mekong can assess options for improving existing flood defences.
Harry Bryden, Jordi Beunk, Sybren Drijfhout, Wilco Hazeleger, and Jennifer Mecking
Ocean Sci., 20, 589–599, https://doi.org/10.5194/os-20-589-2024, https://doi.org/10.5194/os-20-589-2024, 2024
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There is widespread interest in whether the Gulf Stream will decline under global warming. We analyse 19 coupled climate model projections of the AMOC over the 21st century. The model consensus is that the AMOC will decline by about 40 % due to reductions in northward Gulf Stream transport and southward deep western boundary current transport. Whilst the wind-driven Gulf Stream decreases by 4 Sv, most of the decrease in the Gulf Stream is due to a reduction of 7 Sv in its thermohaline component.
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
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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.
Alexander T. Archibald, Bablu Sinha, Maria Russo, Emily Matthews, Freya Squires, N. Luke Abraham, Stephane Bauguitte, Thomas Bannan, Thomas Bell, David Berry, Lucy Carpenter, Hugh Coe, Andrew Coward, Peter Edwards, Daniel Feltham, Dwayne Heard, Jim Hopkins, James Keeble, Elizabeth C. Kent, Brian King, Isobel R. Lawrence, James Lee, Claire R. Macintosh, Alex Megann, Ben I. Moat, Katie Read, Chris Reed, Malcolm Roberts, Reinhard Schiemann, David Schroeder, Tim Smyth, Loren Temple, Navaneeth Thamban, Lisa Whalley, Simon Williams, Huihui Wu, and Ming-Xi Yang
Earth Syst. Sci. Data Discuss., https://doi.org/10.5194/essd-2023-405, https://doi.org/10.5194/essd-2023-405, 2024
Revised manuscript accepted for ESSD
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Here we present an overview of the data generated as part of the North Atlantic Climate System Integrated Studies (ACSIS) programme which are available through dedicated repositories at the Centre for Environmental Data Analysis (CEDA, www.ceda.ac.uk) and the British Oceanographic Data Centre (BODC, bodc.ac.uk). ACSIS data cover the full North Atlantic System comprising: the North Atlantic Ocean, the atmosphere above it including its composition, Arctic Sea Ice and the Greenland Ice Sheet.
Guillaume Gastineau, Claude Frankignoul, Yongqi Gao, Yu-Chiao Liang, Young-Oh Kwon, Annalisa Cherchi, Rohit Ghosh, Elisa Manzini, Daniela Matei, Jennifer Mecking, Lingling Suo, Tian Tian, Shuting Yang, and Ying Zhang
The Cryosphere, 17, 2157–2184, https://doi.org/10.5194/tc-17-2157-2023, https://doi.org/10.5194/tc-17-2157-2023, 2023
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Snow cover variability is important for many human activities. This study aims to understand the main drivers of snow cover in observations and models in order to better understand it and guide the improvement of climate models and forecasting systems. Analyses reveal a dominant role for sea surface temperature in the Pacific. Winter snow cover is also found to have important two-way interactions with the troposphere and stratosphere. No robust influence of the sea ice concentration is found.
Matthew Clark, Robert Marsh, and James Harle
Ocean Sci., 18, 549–564, https://doi.org/10.5194/os-18-549-2022, https://doi.org/10.5194/os-18-549-2022, 2022
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The European Slope Current (SC) is a northward-flowing current running parallel to the UK coastline. It is forced by changes in the density gradient of the wider North Atlantic Ocean. As the North Atlantic has warmed since the late 1990s, these gradients have changed strength and moved, reducing the volume and speed of water feeding into the SC. The SC flows into the North Sea, where changes in the species distribution of some plankton and fish have been seen due to the warming inputs.
Amin Shoari Nejad, Andrew C. Parnell, Alice Greene, Peter Thorne, Brian P. Kelleher, Robert J. N. Devoy, and Gerard McCarthy
Ocean Sci., 18, 511–522, https://doi.org/10.5194/os-18-511-2022, https://doi.org/10.5194/os-18-511-2022, 2022
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We have collated multiple sources of tide gauge data for Dublin Port, and subsequently corrected them for bias. We have then shown that these corrected mean sea level measurements agree with nearby tide gauges to a far higher degree than the raw data. A longer-term comparison with Brest and Newlyn also indicates overall agreement. Our final adjusted dataset estimated the rate of sea level rise to be 1.1 mm/yr between 1953 and 2016 and 7 mm/yr between 1997 and 2016 at Dublin Port.
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
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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.
David T. Pugh, Edmund Bridge, Robin Edwards, Peter Hogarth, Guy Westbrook, Philip L. Woodworth, and Gerard D. McCarthy
Ocean Sci., 17, 1623–1637, https://doi.org/10.5194/os-17-1623-2021, https://doi.org/10.5194/os-17-1623-2021, 2021
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Observations of sea level, taken manually by reading a tide pole, were carefully taken at a number of locations around Ireland in 1842 as part of the first land survey of Ireland. Our study investigates how useful this type of sea level observation is for understanding mean sea level and tidal change. We find that when carefully adjusted for seasonal, meteorological, and astronomical factors, these data can provide important insights into changing sea levels.
Samuel Tiéfolo Diabaté, Didier Swingedouw, Joël Jean-Marie Hirschi, Aurélie Duchez, Philip J. Leadbitter, Ivan D. Haigh, and Gerard D. McCarthy
Ocean Sci., 17, 1449–1471, https://doi.org/10.5194/os-17-1449-2021, https://doi.org/10.5194/os-17-1449-2021, 2021
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The Gulf Stream and the Kuroshio are major currents of the North Atlantic and North Pacific, respectively. They transport warm water northward and are key components of the Earth climate system. For this study, we looked at how they affect the sea level of the coasts of Japan, the USA and Canada. We found that the inshore sea level
co-varies with the north-to-south shifts of the Gulf Stream and Kuroshio. In the paper, we discuss the physical mechanisms that could explain the agreement.
Paul R. Halloran, Jennifer K. McWhorter, Beatriz Arellano Nava, Robert Marsh, and William Skirving
Geosci. Model Dev., 14, 6177–6195, https://doi.org/10.5194/gmd-14-6177-2021, https://doi.org/10.5194/gmd-14-6177-2021, 2021
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This paper describes the latest version of a simple model for simulating coastal oceanography in response to changes in weather and climate. The latest revision of this model makes scientific improvements but focuses on improvements that allow the model to be run simply at large scales and for long periods of time to explore the implications of (for example) future climate change along large areas of coastline.
Gandy Maria Rosales Quintana, Robert Marsh, and Luis Alfredo Icochea Salas
Ocean Sci., 17, 1385–1402, https://doi.org/10.5194/os-17-1385-2021, https://doi.org/10.5194/os-17-1385-2021, 2021
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The Equatorial Undercurrent (EUC) is a key influence on upwelling of nutrient-rich waters associated ecosystems off Peru. To quantify this influence, we backtrack upwelling waters in a computer model of ocean currents, annually, over 1989–2007. The EUC influence varies from year to year, dominating in warm El Niño years, when the EUC extends much closer to the Peruvian coast. In other years, more
localupwelling is associated with coastal winds, coincident with major key population shifts.
Alejandra Sanchez-Franks, Eleanor Frajka-Williams, Ben I. Moat, and David A. Smeed
Ocean Sci., 17, 1321–1340, https://doi.org/10.5194/os-17-1321-2021, https://doi.org/10.5194/os-17-1321-2021, 2021
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In the North Atlantic, ocean currents carry warm surface waters northward and return cooler deep waters southward. This type of ocean circulation, known as overturning, is important for the Earth’s climate. This overturning has been measured using a mooring array at 26° N in the North Atlantic since 2004. Here we use these mooring data and global satellite data to produce a new method for monitoring the overturning over longer timescales, which could potentially be applied to different latitudes.
Amin Shoari Nejad, Andrew C. Parnell, Alice Greene, Brian P. Kelleher, and Gerard McCarthy
Ocean Sci. Discuss., https://doi.org/10.5194/os-2020-81, https://doi.org/10.5194/os-2020-81, 2020
Publication in OS not foreseen
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Following the concerns regarding the consequences of global warming and sea levels rise around the globe, we decided to evaluate how Dublin bay, as an important metropolitan area, is getting affected. After analysing the recordings of multiple tide gauges that are measuring sea levels in the bay, we found that the sea level has been rising 10 millimeters per year between 2003 and 2015 in the region. Also according to our estimations, sea level rise has not been negative since 1996.
Ben I. Moat, David A. Smeed, Eleanor Frajka-Williams, Damien G. Desbruyères, Claudie Beaulieu, William E. Johns, Darren Rayner, Alejandra Sanchez-Franks, Molly O. Baringer, Denis Volkov, Laura C. Jackson, and Harry L. Bryden
Ocean Sci., 16, 863–874, https://doi.org/10.5194/os-16-863-2020, https://doi.org/10.5194/os-16-863-2020, 2020
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The RAPID 26° N array has been measuring the Atlantic meridional overturning circulation (AMOC) since 2004. Since 2009 the AMOC has, compared with previous years, been in a low state. In 2013–2015, in the northern North Atlantic, strong cooling was observed in the ocean and anticipated to intensify the strength of the AMOC some years later. Here, we analyse the latest results from 26° N and conclude that while the AMOC has increased since 2009, this increase is not statistically significant.
Yang Liu, Jisk Attema, Ben Moat, and Wilco Hazeleger
Earth Syst. Dynam., 11, 77–96, https://doi.org/10.5194/esd-11-77-2020, https://doi.org/10.5194/esd-11-77-2020, 2020
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Poleward meridional energy transport (MET) has significant impact on the climate in the Arctic. In this study, we quantify and intercompare MET at subpolar latitudes from six reanalysis data sets. The results indicate that the spatial distribution and temporal variations of MET differ substantially among the reanalysis data sets. Our study suggests that the MET estimated from reanalyses is useful for the evaluation of energy transports but should be used with great care.
Robert Marsh, Ivan D. Haigh, Stuart A. Cunningham, Mark E. Inall, Marie Porter, and Ben I. Moat
Ocean Sci., 13, 315–335, https://doi.org/10.5194/os-13-315-2017, https://doi.org/10.5194/os-13-315-2017, 2017
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To the west of Britain and Ireland, a strong ocean current follows the steep slope that separates the deep Atlantic and the continental shelf. This “Slope Current” exerts an Atlantic influence on the North Sea and its ecosystems. Using a combination of computer modelling and archived data, we find that the Slope Current weakened over 1988–2007, reducing Atlantic influence on the North Sea, due to a combination of warming of the subpolar North Atlantic and weakening winds to the west of Scotland.
E. Frajka-Williams, C. S. Meinen, W. E. Johns, D. A. Smeed, A. Duchez, A. J. Lawrence, D. A. Cuthbertson, G. D. McCarthy, H. L. Bryden, M. O. Baringer, B. I. Moat, and D. Rayner
Ocean Sci., 12, 481–493, https://doi.org/10.5194/os-12-481-2016, https://doi.org/10.5194/os-12-481-2016, 2016
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The ocean meridional overturning circulation (MOC) is predicted by climate models to slow down in this century, resulting in reduced transport of heat northward to mid-latitudes. At 26° N, the Atlantic MOC has been measured continuously for the past decade (2004–2014). In this paper, we discuss the 10-year record of variability, identify the origins of the continued weakening of the circulation, and discuss high-frequency (subannual) compensation between transport components.
P. Achtert, I. M. Brooks, B. J. Brooks, B. I. Moat, J. Prytherch, P. O. G. Persson, and M. Tjernström
Atmos. Meas. Tech., 8, 4993–5007, https://doi.org/10.5194/amt-8-4993-2015, https://doi.org/10.5194/amt-8-4993-2015, 2015
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Doppler lidar wind measurements were obtained during a 3-month Arctic cruise in summer 2014. Ship-motion effects were compensated by combining a commercial Doppler lidar with a custom-made motion-stabilisation platform. This enables the retrieval of wind profiles in the Arctic boundary layer with uncertainties comparable to land-based lidar measurements and standard radiosondes. The presented set-up has the potential to facilitate continuous ship-based wind profile measurements over the oceans.
R. Marsh, A. E. Hickman, and J. Sharples
Geosci. Model Dev., 8, 3163–3178, https://doi.org/10.5194/gmd-8-3163-2015, https://doi.org/10.5194/gmd-8-3163-2015, 2015
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Our relatively shallow shelf seas are warmed at the surface in spring and summer, while strong tidal currents act to mix away the surface warmth. These competing effects strongly influence the conditions for seasonal growth of the phytoplankton that support marine food webs. We have developed a versatile framework for fast computer modelling of shelf seas, to explore seasonal and year-to-year variations of warming and plankton productivity, tested against observations in different regions.
J. Prytherch, M. J. Yelland, I. M. Brooks, D. J. Tupman, R. W. Pascal, B. I. Moat, and S. J. Norris
Atmos. Chem. Phys., 15, 10619–10629, https://doi.org/10.5194/acp-15-10619-2015, https://doi.org/10.5194/acp-15-10619-2015, 2015
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Signals at scales associated with wave and platform motion are often apparent in ship-based turbulent flux measurements, but it has been uncertain whether this is due to measurement error or to wind-wave interactions. We show that the signal has a dependence on horizontal ship velocity and that removing the signal reduces the dependence of the momentum flux on the orientation of the ship to the wind. We conclude that the signal is a bias due to time-varying motion-dependent flow distortion.
R. Marsh, V. O. Ivchenko, N. Skliris, S. Alderson, G. R. Bigg, G. Madec, A. T. Blaker, Y. Aksenov, B. Sinha, A. C. Coward, J. Le Sommer, N. Merino, and V. B. Zalesny
Geosci. Model Dev., 8, 1547–1562, https://doi.org/10.5194/gmd-8-1547-2015, https://doi.org/10.5194/gmd-8-1547-2015, 2015
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Calved icebergs account for around 50% of total freshwater input to the ocean from the Greenland and Antarctic ice sheets. As they melt, icebergs interact with the ocean. We have developed and tested interactive icebergs in a state-of-the-art global ocean model, showing how sea ice, temperatures, and currents are disturbed by iceberg melting. With this new model capability, we are better prepared to predict how future increases in iceberg numbers might influence the oceans and climate.
D. A. Smeed, G. D. McCarthy, S. A. Cunningham, E. Frajka-Williams, D. Rayner, W. E. Johns, C. S. Meinen, M. O. Baringer, B. I. Moat, A. Duchez, and H. L. Bryden
Ocean Sci., 10, 29–38, https://doi.org/10.5194/os-10-29-2014, https://doi.org/10.5194/os-10-29-2014, 2014
S. J. Norris, I. M. Brooks, B. I. Moat, M. J. Yelland, G. de Leeuw, R. W. Pascal, and B. Brooks
Ocean Sci., 9, 133–145, https://doi.org/10.5194/os-9-133-2013, https://doi.org/10.5194/os-9-133-2013, 2013
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
Mixing and air–sea buoyancy fluxes set the time-mean overturning circulation in the subpolar North Atlantic and Nordic Seas
Observation-based estimates of volume, heat, and freshwater exchanges between the subpolar North Atlantic interior, its boundary currents, and the atmosphere
Dafydd Gwyn Evans, N. Penny Holliday, Sheldon Bacon, and Isabela Le Bras
Ocean Sci., 19, 745–768, https://doi.org/10.5194/os-19-745-2023, https://doi.org/10.5194/os-19-745-2023, 2023
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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.
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
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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.
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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.
The RAPID array has observed the Atlantic meridional overturning circulation (AMOC) since 2004,...
