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  1. Article ; Online: Contrasting internally and externally generated Atlantic Multidecadal Variability and the role for AMOC in CMIP6 historical simulations.

    Robson, Jon / Sutton, Rowan / Menary, Matthew B / Lai, Michael W K

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

    2023  Volume 381, Issue 2262, Page(s) 20220194

    Abstract: Atlantic multidecadal variability (AMV) has long been thought to be an expression of low-frequency variability in the Atlantic Meridional Overturning Circulation (AMOC). However, alternative hypotheses have been forwarded, including that AMV is primarily ...

    Abstract Atlantic multidecadal variability (AMV) has long been thought to be an expression of low-frequency variability in the Atlantic Meridional Overturning Circulation (AMOC). However, alternative hypotheses have been forwarded, including that AMV is primarily externally forced. Here, we review the current state of play by assessing historical simulations made for the sixth coupled model intercomparison project (CMIP6). Overall, the importance of external forcing is sensitive to the type of AMV index used, due to the importance of globally coherent externally forced signals in the models. There are also significant contrasts between the processes that drive internally and externally forced AMV, but these processes can be isolated by exploring the multivariate expression of AMV. Specifically, internal variability in CMIP6 models is consistent with an important role of ocean circulation and AMOC and the externally forced AMV is largely a surface-flux forced mechanism with little role for the ocean. Overall, the internal multivariate fingerprint of AMV is similar to the observed, but the externally forced fingerprint appears inconsistent with observations. Therefore, climate models still suggest a key role for ocean dynamics, and specifically AMOC, in observed AMV. Nevertheless, models remain deficient in a number of areas, and a stronger role for externally forced dynamical changes cannot be ruled out. This article is part of a discussion meeting issue 'Atlantic overturning: new observations and challenges'.
    Language English
    Publishing date 2023-10-23
    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.2022.0194
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Limits on determining the skill of North Atlantic Ocean decadal predictions.

    Menary, Matthew B / Hermanson, Leon

    Nature communications

    2018  Volume 9, Issue 1, Page(s) 1694

    Abstract: The northern North Atlantic is important globally both through its impact on the Atlantic Meridional Overturning Circulation (AMOC) and through widespread atmospheric teleconnections. The region has been shown to be potentially predictable a decade ahead ...

    Abstract The northern North Atlantic is important globally both through its impact on the Atlantic Meridional Overturning Circulation (AMOC) and through widespread atmospheric teleconnections. The region has been shown to be potentially predictable a decade ahead with the skill of decadal predictions assessed against reanalyses of the ocean state. Here, we show that the prediction skill in this region is strongly dependent on the choice of reanalysis used for validation, and describe the causes. Multiannual skill in key metrics such as Labrador Sea density and the AMOC depends on more than simply the choice of the prediction model. Instead, this skill is related to the similarity between the nature of interannual density variability in the underlying climate model and the chosen reanalysis. The climate models used in these decadal predictions are also used in climate projections, which raises questions about the sensitivity of these projections to the models' innate North Atlantic density variability.
    Language English
    Publishing date 2018-04-27
    Publishing country England
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2553671-0
    ISSN 2041-1723 ; 2041-1723
    ISSN (online) 2041-1723
    ISSN 2041-1723
    DOI 10.1038/s41467-018-04043-9
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article: An anatomy of the projected North Atlantic warming hole in CMIP5 models

    Menary, MatthewB / Richard A. Wood

    Climate dynamics. 2018 Apr., v. 50, no. 7-8

    2018  

    Abstract: Global mean surface air temperature has increased over the past century and climate models project this trend to continue. However, the pattern of change is not homogeneous. Of particular interest is the subpolar North Atlantic, which has cooled in ... ...

    Abstract Global mean surface air temperature has increased over the past century and climate models project this trend to continue. However, the pattern of change is not homogeneous. Of particular interest is the subpolar North Atlantic, which has cooled in recent years and is projected to continue to warm less rapidly than the global mean. This is often termed the North Atlantic warming hole (WH). In climate model projections, the development of the WH is concomitant with a weakening of the Atlantic meridional overturning circulation (AMOC). Here, we further investigate the possible link between the AMOC and WH and the competing drivers of vertical mixing and surface heat fluxes. Across a large ensemble of 41 climate models we find that the spatial structure of the WH varies considerably from model to model but is generally upstream of the simulated deep water formation regions. A heat budget analysis suggests the formation of the WH is related to changes in ocean heat transport. Although the models display a plethora of AMOC mean states, they generally predict a weakening and shallowing of the AMOC also consistent with the evolving depth structure of the WH. A lagged regression analysis during the WH onset phase suggests that reductions in wintertime mixing lead a weakening of the AMOC by 5 years in turn leading initiation of the WH by 5 years. Inter-model differences in the evolution and structure of the WH are likely to lead to somewhat different projected climate impacts in nearby Europe and North America.
    Keywords air temperature ; climate ; climate models ; heat transfer ; mixing ; regression analysis ; winter ; Europe ; North America
    Language English
    Dates of publication 2018-04
    Size p. 3063-3080.
    Publishing place Springer Berlin Heidelberg
    Document type Article
    ZDB-ID 1471747-5
    ISSN 1432-0894 ; 0930-7575
    ISSN (online) 1432-0894
    ISSN 0930-7575
    DOI 10.1007/s00382-017-3793-8
    Database NAL-Catalogue (AGRICOLA)

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  4. Article: Systematic investigation of skill opportunities in decadal prediction of air temperature over Europe

    Sgubin, Giovanni / Swingedouw, Didier / Borchert, Leonard F. / Menary, Matthew B. / Noël, Thomas / Loukos, Harilaos / Mignot, Juliette

    Climate dynamics. 2021 Dec., v. 57, no. 11-12

    2021  

    Abstract: Decadal Climate Predictions (DCP) have gained considerable attention for their potential utility in promoting optimised plans of adaptation to climate change and variability. Their effective applicability to a targeted problem is nevertheless conditional ...

    Abstract Decadal Climate Predictions (DCP) have gained considerable attention for their potential utility in promoting optimised plans of adaptation to climate change and variability. Their effective applicability to a targeted problem is nevertheless conditional on a detailed evaluation of their ability to simulate the near-term climate evolution under specific conditions. Here we explore the performance of the IPSL-CM5A-LR DCP system in predicting air temperature over Europe, by proposing a systematic assessessment of the prediction skill for different time windows (periods of the calendar time, forecast years and months/seasons). In this framework, we also compare raw and de-biased hindcasts, in which the temperature outputs have been corrected using a quantile matching method. The systematic analysis allows to discern certain conditions conferring larger predictability, which we find to be intermittent in time. The predictions appear more skilful around the 1960s and after the 1980s, in coincidence with large shifts of the Atlantic Multidecadal Variability, which are well reproduced in the hindcasts. Averages on longer forecast periods also generally imply better prediction skill, while the best predicted months appear to be mainly those between late spring and early autumn. Moreover, we find an overall added value due to initialisation, while de-biased predictions significantly outperform raw predictions only for a few specific time windows. Finally, we discuss the potential implications of the proposed systematic exploration of skill opportunities in DCPs for integrated applications in climate sensitive sectors.
    Keywords air temperature ; autumn ; climate ; climate change ; climatology ; dynamics ; prediction ; spring ; Europe
    Language English
    Dates of publication 2021-12
    Size p. 3245-3263.
    Publishing place Springer Berlin Heidelberg
    Document type Article
    ZDB-ID 1471747-5
    ISSN 1432-0894 ; 0930-7575
    ISSN (online) 1432-0894
    ISSN 0930-7575
    DOI 10.1007/s00382-021-05863-0
    Database NAL-Catalogue (AGRICOLA)

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  5. Article ; Online: Challenges simulating the AMOC in climate models.

    Jackson, Laura C / Hewitt, Helene T / Bruciaferri, Diego / Calvert, Daley / Graham, Tim / Guiavarc'h, Catherine / Menary, Matthew B / New, Adrian L / Roberts, Malcolm / Storkey, David

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

    2023  Volume 381, Issue 2262, Page(s) 20220187

    Abstract: The latest assessment report from the Intergovernmental Panel on Climate Change concluded that the Atlantic Meridional Overturning Circulation (AMOC) was very likely to decline over the twenty-first century under all emissions scenarios; however, there ... ...

    Abstract The latest assessment report from the Intergovernmental Panel on Climate Change concluded that the Atlantic Meridional Overturning Circulation (AMOC) was very likely to decline over the twenty-first century under all emissions scenarios; however, there was low confidence in the magnitude of the decline. Recent research has highlighted that model biases in the mean climate state can affect the AMOC in its mean state, variability and its response to climate change. Hence, understanding and reducing these model biases is critical for reducing uncertainty in the future changes of the AMOC and in its impacts on the wider climate. We discuss how model biases, in particular salinity biases, influence the AMOC and deep convection. We then focus on biases in the UK HadGEM3-GC3-1 climate model and how these biases change with resolution. We also discuss ongoing model development activities that affect these biases, and highlight priorities for improved representation of processes, such as the position of the North Atlantic Current, transports in narrow boundary current, resolution (or improved parameterization) of eddies and spurious numerical mixing in overflows. This article is part of a discussion meeting issue 'Atlantic overturning: new observations and challenges'.
    Language English
    Publishing date 2023-10-23
    Publishing country England
    Document type Journal Article ; Review
    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.2022.0187
    Database MEDical Literature Analysis and Retrieval System OnLINE

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    In stock of ZB MED Bonn / Germany

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  6. Article: Naturally forced multidecadal variability of the Atlantic meridional overturning circulation

    Menary, Matthew B / Scaife, Adam A

    Climate dynamics. 2014 Mar., v. 42, no. 5-6

    2014  

    Abstract: The mechanisms by which natural forcing factors alone could drive simulated multidecadal variability in the Atlantic meridional overturning circulation (AMOC) are assessed in an ensemble of climate model simulations. It is shown for a new state-of-the- ... ...

    Abstract The mechanisms by which natural forcing factors alone could drive simulated multidecadal variability in the Atlantic meridional overturning circulation (AMOC) are assessed in an ensemble of climate model simulations. It is shown for a new state-of-the-art general circulation model, HadGEM2-ES, that the most important of these natural forcings, in terms of the multidecadal response of the AMOC, is solar rather than volcanic forcing. AMOC strengthening occurs through a densification of the North Atlantic, driven by anomalous surface freshwater fluxes due to increased evaporation. These are related to persistent North Atlantic atmospheric circulation anomalies, driven by forced changes in the stratosphere, associated with anomalously weak solar irradiance during the late nineteenth and early twentieth centuries. Within a period of approximately 100 years the 11-year smoothed ensemble mean AMOC strengthens by 1.5 Sv and subsequently weakens by 1.9 Sv, representing respectively approximately 3 and 4 standard deviations of the 11-year smoothed control simulation. The solar-induced variability of the AMOC has various relevant climate impacts, such as a northward shift of the intertropical convergence zone, anomalous Amazonian rainfall, and a sustained increase in European temperatures. While this model has only a partial representation of the atmospheric response to solar variability, these results demonstrate the potential for solar variability to have a multidecadal impact on North Atlantic climate.
    Keywords General Circulation Models ; atmospheric circulation ; climate ; evaporation ; freshwater ; rain ; simulation models ; solar radiation ; stratosphere ; temperature
    Language English
    Dates of publication 2014-03
    Size p. 1347-1362.
    Publishing place Springer-Verlag
    Document type Article
    ZDB-ID 1471747-5
    ISSN 1432-0894 ; 0930-7575
    ISSN (online) 1432-0894
    ISSN 0930-7575
    DOI 10.1007/s00382-013-2028-x
    Database NAL-Catalogue (AGRICOLA)

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  7. Article: Nonlinear regional warming with increasing CO2 concentrations

    Good, Peter / Lowe, Jason A. / Andrews, Timothy / Wiltshire, Andrew / Chadwick, Robin / Ridley, Jeff K. / Menary, Matthew B. / Bouttes, Nathaelle / Dufresne, Jean Louis / Gregory, Jonathan M. / Schaller, Nathalie / Shiogama, Hideo

    Nature climate change

    2015  Volume 5, Issue 2, Page(s) 138

    Language English
    Document type Article
    ZDB-ID 2614383-5
    ISSN 1758-678x
    Database Current Contents Nutrition, Environment, Agriculture

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