Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Reintges, Annika; Martin, Torge; Latif, Mojib; Park, Wonsun

doi:10.1002/2017gl074087

Cited by 30 publications

(32 citation statements)

References 39 publications

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“…We find four multiyear MRP events and, 20 in each event, (deep) convection causes vertical mixing of anomalous subsurface heat towards the surface where it melts the sea-ice and leads to the formation of the MRP. These processes of the formation and lifecycle of the MRP are broadly in agreement with the classical view as in Martinson et al (1981) and those described from other model results in Martin et al (2013), Dufour et al (2017) and Reintges et al (2017).…”

Section: Summary and Discussionsupporting

confidence: 91%

“…During an MRP event, the mixed layer depth increases, positive subsurface heat and salt anomalies are mixed towards the surface leading there to positive surface anomalies. The surface heat anomalies lead to sea-ice melt and consequently to polynya 5 formation, in agreement with earlier studies(Martin et al, 2013;Dufour et al, 2017;Reintges et al, 2017).The variability associated with the SOM can be measured via the SOM index which is defined as the temperature anomalyover the region 0 • W -50 • W × 35 • S -50 • S (LeBars et al, 2016). The SOM index (shown as the red curve inFigure 3a)displays also multidecadal variability.…”

supporting

confidence: 87%

“…the eddying-version of the same model. The results in Dufour et al (2017) and Weijer et al (2017) suggest that ocean eddies (and also overflows) play a significant role in the vertical background stratification (in addition to the effects already mentioned by Reintges et al (2017)) and therefore affect the time scale of the occurrence of deep convection.…”

mentioning

confidence: 77%

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Multidecadal Preconditioning of the Maud Rise Polynya Region

Westen¹,

Dijkstra²

2020

Preprint

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Abstract. In this paper, we consider Maud Rise polynya formation in a long (250 years) high-resolution (ocean 0.1°, atmosphere 0.5° horizontal model resolution) of the Community Earth System Model. We find a dominant multidecadal time scale in the occurrence of these Maud Rise polynyas. Analysis of the results leads us to the interpretation that a preferred time scale can be induced by the variability of the Weddell Gyre, previously identified as the Southern Ocean Mode. The large-scale pattern of heat content variability associated with the Southern Ocean Mode modifies the stratification in the Maud Rise region and leads to a preferred time scale in convection through preconditioning of the subsurface density, and consequently to polynya formation.

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Section: Summary and Discussionsupporting

confidence: 91%

supporting

confidence: 87%

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Multidecadal Preconditioning of the Maud Rise Polynya Region

Westen¹,

Dijkstra²

2020

Preprint

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“…The Southern Ocean exhibits large multi-century oscillations in surface temperature and sea ice extent. Further work is in progress to understand the mechanisms behind this variability, but there is a growing body of evidence which indicates that such oscillations may be a feature of the natural state of the Earth system (e.g., Kurtakoti et al, 2018;Reintges et al, 2017;Zhang et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

UKESM1: Description and Evaluation of the U.K. Earth System Model

Sellar

Jones

Mulcahy

et al. 2019

J Adv Model Earth Syst

601

461

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We document the development of the first version of the U.K. Earth System Model UKESM1.The model represents a major advance on its predecessor HadGEM2-ES, with enhancements to all component models and new feedback mechanisms. These include a new core physical model with a well-resolved stratosphere; terrestrial biogeochemistry with coupled carbon and nitrogen cycles and enhanced land management; tropospheric-stratospheric chemistry allowing the holistic simulation of radiative forcing from ozone, methane, and nitrous oxide; two-moment, five-species, modal aerosol; and ocean biogeochemistry with two-way coupling to the carbon cycle and atmospheric aerosols. The complexity of coupling between the ocean, land, and atmosphere physical climate and biogeochemical cycles in UKESM1 is unprecedented for an Earth system model. We describe in detail the process by which the coupled model was developed and tuned to achieve acceptable performance in key physical and Earth system quantities and discuss the challenges involved in mitigating biases in a model with complex connections between its components. Overall, the model performs well, with a stable pre-industrial state and good agreement with observations in the latter period of its historical simulations. However, global mean surface temperature exhibits stronger-than-observed cooling from 1950 to 1970, followed by rapid warming from 1980 to 2014. Metrics from idealized simulations show a high climate sensitivity relative to previous generations of models: Equilibrium climate sensitivity is 5.4 K, transient climate response ranges from 2.68 to 2.85 K, and transient climate response to cumulative emissions is 2.49 to 2.66 K TtC −1 . Plain Language SummaryWe describe the development and behavior of UKESM1, a novel climate model that includes improved representations of processes in the atmosphere, ocean, and on land. These processes are inter-related: For example, dust is produced on the land and blown up into the atmosphere where it affects the amount of sunlight falling on Earth. Dust can also be dissolved in the ocean, where it affects marine life. This in turn changes both the amount of carbon dioxide absorbed by the ocean and the material emitted from the surface into the atmosphere, which has an affect on the formation of clouds. UKESM1 includes many processes and interactions such as these, giving it a high level of complexity. Ensuring realistic process behavior is a major challenge in the development of our model, and we have carefully tested this. UKESM1 performs well, correctly exhibiting stable results from a continuous pre-industrial simulation (used to provide a reference for future experiments) and showing good agreement

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“…A slower vertical ocean mixing (kv low) results in a slower air‐sea gas exchange, postponing therefore the ocean deep convection event whereas faster vertical ocean mixing brings the event forward. These highly variable deep convection events appear in model runs with and without CDR and are influenced by several factors such as stratification strength and sea ice volume (Reintges et al, ).…”

Section: Resultsmentioning

confidence: 99%

Integrated Assessment of Carbon Dioxide Removal

et al. 2018

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To maintain the chance of keeping the average global temperature increase below 2°C and to limit long‐term climate change, removing carbon dioxide from the atmosphere (carbon dioxide removal, CDR) is becoming increasingly necessary. We analyze optimal and cost‐effective climate policies in the dynamic integrated assessment model (IAM) of climate and the economy (DICE2016R) and investigate (1) the utilization of (ocean) CDR under different climate objectives, (2) the sensitivity of policies with respect to carbon cycle feedbacks, and (3) how well carbon cycle feedbacks are captured in the carbon cycle models used in state‐of‐the‐art IAMs. Overall, the carbon cycle model in DICE2016R shows clear improvements compared to its predecessor, DICE2013R, capturing much better long‐term dynamics and also oceanic carbon outgassing due to excess oceanic storage of carbon from CDR. However, this comes at the cost of a (too) tight short‐term remaining emission budget, limiting the model suitability to analyze low‐emission scenarios accurately. With DICE2016R, the compliance with the 2°C goal is no longer feasible without negative emissions via CDR. Overall, the optimal amount of CDR has to take into account (1) the emission substitution effect and (2) compensation for carbon cycle feedbacks.

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Physical controls of Southern Ocean deep‐convection variability in CMIP5 models and the Kiel Climate Model

Cited by 30 publications

References 39 publications

Multidecadal Preconditioning of the Maud Rise Polynya Region

Multidecadal Preconditioning of the Maud Rise Polynya Region

UKESM1: Description and Evaluation of the U.K. Earth System Model

Integrated Assessment of Carbon Dioxide Removal

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