On the Abruptness of Bølling–Allerød Warming

Abstract Previous observations and simulations suggest that an approximate 3°–5°C warming occurred at intermediate depths in the North Atlantic over several millennia during Heinrich stadial 1 (HS1), which induces warm salty water (WSW) lying beneath surface cold freshwater. This arrangement eventually generates ocean convective available potential energy (OCAPE), the maximum potential energy releasable by adiabatic vertical parcel rearrangements in an ocean column. The authors find that basin-scale OCAPE starts to appear in the North Atlantic (~67.5°–73.5°N) and builds up over decades at the end of HS1 with a magnitude of about 0.05 J kg−1. OCAPE provides a key kinetic energy source for thermobaric cabbeling convection (TCC). Using a high-resolution TCC-resolved regional model, it is found that this decadal-scale accumulation of OCAPE ultimately overshoots its intrinsic threshold and is released abruptly (~1 month) into kinetic energy of TCC, with further intensification from cabbeling. TCC has convective plumes with approximately 0.2–1-km horizontal scales and large vertical displacements (~1 km), which make TCC difficult to be resolved or parameterized by current general circulation models. The simulation herein indicates that these local TCC events are spread quickly throughout the OCAPE-contained basin by internal wave perturbations. Their convective plumes have large vertical velocities (~8–15 cm s−1) and bring the WSW to the surface, causing an approximate 2°C sea surface warming for the whole basin (~700 km) within a month. This exposes a huge heat reservoir to the atmosphere, which helps to explain the abrupt Bølling–Allerød warming.

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North Atlantic 20th century multidecadal variability in coupled climate models: sea surface temperature and ocean overturning circulation

Ocean Science ◽

10.5194/os-7-389-2011 ◽

2011 ◽

Vol 7 (3) ◽

pp. 389-404 ◽

Cited By ~ 75

Author(s):

I. Medhaug ◽

T. Furevik

Keyword(s):

Surface Temperature ◽

20Th Century ◽

North Atlantic ◽

General Circulation ◽

General Circulation Models ◽

Meridional Overturning Circulation ◽

Overturning Circulation ◽

Atlantic Sector ◽

The North ◽

The North Atlantic

Abstract. Output from a total of 24 state-of-the-art Atmosphere-Ocean General Circulation Models is analyzed. The models were integrated with observed forcing for the period 1850–2000 as part of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. All models show enhanced variability at multi-decadal time scales in the North Atlantic sector similar to the observations, but with a large intermodel spread in amplitudes and frequencies for both the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The models, in general, are able to reproduce the observed geographical patterns of warm and cold episodes, but not the phasing such as the early warming (1930s–1950s) and the following colder period (1960s–1980s). This indicates that the observed 20th century extreme in temperatures are due to primarily a fortuitous phasing of intrinsic climate variability and not dominated by external forcing. Most models show a realistic structure in the overturning circulation, where more than half of the available models have a mean overturning transport within the observed estimated range of 13–24 Sverdrup. Associated with a stronger than normal AMOC, the surface temperature is increased and the sea ice extent slightly reduced in the North Atlantic. Individual models show potential for decadal prediction based on the relationship between the AMO and AMOC, but the models strongly disagree both in phasing and strength of the covariability. This makes it difficult to identify common mechanisms and to assess the applicability for predictions.

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The ability of general circulation models to simulate tropical cyclones and their precursors over the North Atlantic main development region

Climate Dynamics ◽

10.1007/s00382-012-1290-7 ◽

2012 ◽

Vol 39 (7-8) ◽

pp. 1559-1576 ◽

Cited By ~ 24

Author(s):

Anne Sophie Daloz ◽

Fabrice Chauvin ◽

Kevin Walsh ◽

Sally Lavender ◽

Deborah Abbs ◽

...

Keyword(s):

Tropical Cyclones ◽

North Atlantic ◽

General Circulation ◽

General Circulation Models ◽

The North ◽

Main Development ◽

Development Region ◽

The North Atlantic

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Direct temporal cascade of temperature variance in eddy-permitting simulations of multidecadal variability

10.5194/egusphere-egu2020-4992 ◽

2020 ◽

Author(s):

Antoine Hochet ◽

Thierry Huck ◽

Olivier Arzel ◽

Florian Sevellec ◽

Alain Colin de Verdiere ◽

...

Keyword(s):

North Atlantic ◽

General Circulation ◽

Numerical Models ◽

Low Frequency ◽

Circulation Model ◽

Temperature Variance ◽

The North ◽

Basin Scale ◽

The North Atlantic ◽

Meso Scale

The North Atlantic is characterized by basin-scale multidecadal fluctuations of the sea surface temperature with periods ranging from 20 to 70 years. One candidate for such a variability is a large-scale baroclinic instability of the North Atlantic Current. Because of the long time scales involved, most of the studies devoted to this problem are based on low resolution numerical models leaving aside the effect of explicit meso-scale eddies. &#160;&#160; How high-frequency motions associated with the meso-scale eddy field affect the basin-scale low-frequency variabiliy is the central question of this study.This issue is addressed using an idealized configuration of an Ocean General Circulation Model at eddy-permitting resolution (20 km). A new diagnostic allowing the calculation of nonlinear fluxes of temperature variance in frequency space is presented. Using this diagnostic, we show that the primary effect of meso-scale eddies is to damp low frequency &#160;temperature variance and to transfer it to high frequencies.

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Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

Climate of the Past Discussions ◽

10.5194/cpd-2-633-2006 ◽

2006 ◽

Vol 2 (4) ◽

pp. 633-656

Author(s):

K. Grosfeld ◽

G. Lohmann ◽

N. Rimbu ◽

K. Fraedrich ◽

F. Lunkeit

Keyword(s):

Climate Variability ◽

Atmospheric Circulation ◽

North Atlantic ◽

General Circulation ◽

Circulation Model ◽

General Circulation Models ◽

Proxy Data ◽

Model Studies ◽

The North ◽

The North Atlantic

Abstract. We investigate the spatial and temporal characteristics of multidecadal climate variability in the North Atlantic realm, using observational data, proxy data and model results. The dominant pattern of multidecadal variability of SST depicts a monopolar structure in the North Atlantic during the instrumental period with cold (warm) phases during 1900–1925 and 1970–1990 (1870–1890 and 1940–1960). Two atmospheric general circulation models of different complexity forced with global SST over the last century show SLP anomaly patterns from the warm and cold phases of the North Atlantic similar to the corresponding observed patterns. The analysis of a sediment core from Cariaco Basin, a coral record from the northern Red Sea, and a long-term sea level pressure (SLP) reconstruction reveals that the multidecadal mode of the atmospheric circulation characterizes climate variability also in the pre-industrial era. The analyses of SLP reconstruction and proxy data depict a persistent atmospheric mode at least over the last 300 years, where SLP shows a dipolar structure in response to monopolar North Atlantic SST, in a similar way as the models' responses do. The combined analysis of observational and proxy data with model experiments provides an understanding of multidecadal climate modes during the late Holocene. The related patterns are useful for the interpretation of proxy data in the North Atlantic realm.

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Atmospheric multidecadal variations in the North Atlantic realm: proxy data, observations, and atmospheric circulation model studies

Climate of the Past ◽

10.5194/cp-3-39-2007 ◽

2007 ◽

Vol 3 (1) ◽

pp. 39-50 ◽

Cited By ~ 31

Author(s):

K. Grosfeld ◽

G. Lohmann ◽

N. Rimbu ◽

K. Fraedrich ◽

F. Lunkeit

Keyword(s):

Climate Variability ◽

Atmospheric Circulation ◽

North Atlantic ◽

General Circulation ◽

Circulation Model ◽

General Circulation Models ◽

Proxy Data ◽

Model Studies ◽

The North ◽

The North Atlantic

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Direct Temporal Cascade of Temperature Variance in Eddy-Permitting Simulations of Multidecadal Variability

Journal of Climate ◽

10.1175/jcli-d-19-0921.1 ◽

2020 ◽

Vol 33 (21) ◽

pp. 9409-9425

Author(s):

Antoine Hochet ◽

Thierry Huck ◽

Olivier Arzel ◽

Florian Sévellec ◽

Alain Colin de Verdière ◽

...

Keyword(s):

North Atlantic ◽

General Circulation ◽

Numerical Models ◽

Mesoscale Eddy ◽

Low Frequency ◽

Mesoscale Eddies ◽

Temperature Variance ◽

The North ◽

Basin Scale ◽

The North Atlantic

AbstractThe North Atlantic is characterized by basin-scale multidecadal fluctuations of the sea surface temperature with periods ranging from 20 to 70 years. One candidate for such a variability is a large-scale baroclinic instability of the temperature gradients across the Atlantic associated with the North Atlantic Current. Because of the long time scales involved, most of the studies devoted to this problem are based on low-resolution numerical models leaving aside the effect of explicit mesoscale eddies. How high-frequency motions associated with the mesoscale eddy field affect the basin-scale low-frequency variability is the central question of this study. This issue is addressed using an idealized configuration of an ocean general circulation model at eddy-permitting resolution (20 km). A new diagnostic allowing the calculation of nonlinear fluxes of temperature variance in frequency space is presented. Using this diagnostic, we show that the primary effect of mesoscale eddies is to damp low-frequency temperature variance and to transfer it to high frequencies.

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North Atlantic 20th century multidecadal variability in coupled climate models: sea surface temperature and ocean overturning circulation

Ocean Science Discussions ◽

10.5194/osd-8-353-2011 ◽

2011 ◽

Vol 8 (1) ◽

pp. 353-396 ◽

Cited By ~ 12

Author(s):

I. Medhaug ◽

T. Furevik

Keyword(s):

Surface Temperature ◽

20Th Century ◽

North Atlantic ◽

General Circulation ◽

General Circulation Models ◽

Meridional Overturning Circulation ◽

Overturning Circulation ◽

Atlantic Sector ◽

The North ◽

The North Atlantic

Abstract. Output from a total of 24 state-of-the-art Atmosphere-Ocean General Circulation Models is analyzed. The models were integrated with observed forcing for the period 1850–2000 as part of the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. All models show enhanced variability at multi-decadal time scales in the North Atlantic sector similar to the observations, but with a large intermodel spread in amplitudes and frequencies for both the Atlantic Multidecadal Oscillation (AMO) and the Atlantic Meridional Overturning Circulation (AMOC). The models, in general, are able to reproduce the observed geographical patterns of warm and cold episodes, but not the phasing such as the early warming (1930s–50s) and the following colder period (1960s–80s). This indicates that the observed 20th century extreme in temperatures are due to primarily a fortuitous phasing of intrinsic climate variability and not dominated by external forcing. Most models show a realistic structure in the overturning circulation, where more than half of the available models have a mean overturning transport within the observed estimated range of 13–24 Sverdrup. Associated with a stronger than normal AMOC, the surface temperature is increased and the sea ice extent slightly reduced in the North Atlantic. Individual models show potential for decadal prediction based on the relationship between the AMO and AMOC, but the models strongly disagree both in phasing and strength of the covariability. This makes it difficult to identify common mechanisms and to assess the applicability for predictions.

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The Marine Environment

10.1093/oso/9780199233267.003.0001 ◽

2017 ◽

Author(s):

N. Penny Holliday ◽

Stephanie Henson

Keyword(s):

Primary Production ◽

North Atlantic ◽

Physical Environment ◽

Seasonal Cycle ◽

Physical Processes ◽

The North ◽

Basin Scale ◽

The North Atlantic ◽

Physical Features ◽

Growth Distribution

The growth, distribution, and variability of phytoplankton populations in the North Atlantic are primarily controlled by the physical environment. This chapter provides an overview of the regional circulation of the North Atlantic, and an introduction to the key physical features and processes that affect ecosystems, and especially plankton, via the availability of light and nutrients. There is a natural seasonal cycle in primary production driven by physical processes that determine the light and nutrient levels, but the pattern has strong regional variations. The variations are determined by persistent features on the basin scale (e.g. the main currents and mixed layer regimes of the subtropical and subpolar gyres), as well as transient mesoscale features such as eddies and meanders of fronts.

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Transport and storage of anthropogenic C in the North Atlantic Subpolar Ocean

Biogeosciences ◽

10.5194/bg-15-4661-2018 ◽

2018 ◽

Vol 15 (14) ◽

pp. 4661-4682 ◽

Cited By ~ 1

Author(s):

Virginie Racapé ◽

Patricia Zunino ◽

Herlé Mercier ◽

Pascale Lherminier ◽

Laurent Bopp ◽

...

Keyword(s):

Interannual Variability ◽

North Atlantic ◽

General Circulation ◽

Meridional Overturning Circulation ◽

Intermediate Water ◽

Data Set ◽

The North ◽

Storage Rate ◽

The North Atlantic ◽

And Storage

Abstract. The North Atlantic Ocean is a major sink region for atmospheric CO2 and contributes to the storage of anthropogenic carbon (Cant). While there is general agreement that the intensity of the meridional overturning circulation (MOC) modulates uptake, transport and storage of Cant in the North Atlantic Subpolar Ocean, processes controlling their recent variability and evolution over the 21st century remain uncertain. This study investigates the relationship between transport, air–sea flux and storage rate of Cant in the North Atlantic Subpolar Ocean over the past 53 years. Its relies on the combined analysis of a multiannual in situ data set and outputs from a global biogeochemical ocean general circulation model (NEMO–PISCES) at 1∕2∘ spatial resolution forced by an atmospheric reanalysis. Despite an underestimation of Cant transport and an overestimation of anthropogenic air–sea CO2 flux in the model, the interannual variability of the regional Cant storage rate and its driving processes were well simulated by the model. Analysis of the multi-decadal simulation revealed that the MOC intensity variability was the major driver of the Cant transport variability at 25 and 36∘ N, but not at OVIDE. At the subpolar OVIDE section, the interannual variability of Cant transport was controlled by the accumulation of Cant in the MOC upper limb. At multi-decadal timescales, long-term changes in the North Atlantic storage rate of Cant were driven by the increase in air–sea fluxes of anthropogenic CO2. North Atlantic Central Water played a key role for storing Cant in the upper layer of the subtropical region and for supplying Cant to Intermediate Water and North Atlantic Deep Water. The transfer of Cant from surface to deep waters occurred mainly north of the OVIDE section. Most of the Cant transferred to the deep ocean was stored in the subpolar region, while the remainder was exported to the subtropical gyre within the lower MOC.

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Marine productivity response to Heinrich events: a model-data comparison

Climate of the Past ◽

10.5194/cp-8-1581-2012 ◽

2012 ◽

Vol 8 (5) ◽

pp. 1581-1598 ◽

Cited By ~ 23

Author(s):

V. Mariotti ◽

L. Bopp ◽

A. Tagliabue ◽

M. Kageyama ◽

D. Swingedouw

Keyword(s):

North Atlantic ◽

General Circulation ◽

Circulation Model ◽

Global Ocean ◽

Biogeochemical Model ◽

Heinrich Events ◽

The North ◽

Heinrich Event ◽

The North Atlantic ◽

Marine Productivity

Abstract. Marine sediments records suggest large changes in marine productivity during glacial periods, with abrupt variations especially during the Heinrich events. Here, we study the response of marine biogeochemistry to such an event by using a biogeochemical model of the global ocean (PISCES) coupled to an ocean-atmosphere general circulation model (IPSL-CM4). We conduct a 400-yr-long transient simulation under glacial climate conditions with a freshwater forcing of 0.1 Sv applied to the North Atlantic to mimic a Heinrich event, alongside a glacial control simulation. To evaluate our numerical results, we have compiled the available marine productivity records covering Heinrich events. We find that simulated primary productivity and organic carbon export decrease globally (by 16% for both) during a Heinrich event, albeit with large regional variations. In our experiments, the North Atlantic displays a significant decrease, whereas the Southern Ocean shows an increase, in agreement with paleo-productivity reconstructions. In the Equatorial Pacific, the model simulates an increase in organic matter export production but decreased biogenic silica export. This antagonistic behaviour results from changes in relative uptake of carbon and silicic acid by diatoms. Reasonable agreement between model and data for the large-scale response to Heinrich events gives confidence in models used to predict future centennial changes in marine production. In addition, our model allows us to investigate the mechanisms behind the observed changes in the response to Heinrich events.

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