Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age

Knudsen, Mads Faurschou; Jacobsen, Bo Holm; Seidenkrantz, Marit‐Solveig; Olsen, Jesper

doi:10.1038/ncomms4323

Cited by 126 publications

(109 citation statements)

References 60 publications

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“…Aerosol release by volcanic eruptions has been suggested to act as an external driver of AMV in the preindustrial period (Ottera et al, 2010;Knudsen et al, 2014), contrary to other studies that suggest that AMV is internally driven by oceanatmosphere interactions. Over the industrial period, the role of anthropogenic aerosols in driving AMV also remains an open question.…”

Section: H K a Singh Et Al: Amo In The Lmrcontrasting

confidence: 43%

Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

et al. 2018

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Abstract. The Last Millennium Reanalysis (LMR) employs a data assimilation approach to reconstruct climate fields from annually resolved proxy data over years 0-2000 CE. We use the LMR to examine Atlantic multidecadal variability (AMV) over the last 2 millennia and find several robust thermodynamic features associated with a positive Atlantic Multidecadal Oscillation (AMO) index that reveal a dynamically consistent pattern of variability: the Atlantic and most continents warm; sea ice thins over the Arctic and retreats over the Greenland, Iceland, and Norwegian seas; and equatorial precipitation shifts northward. The latter is consistent with anomalous southward energy transport mediated by the atmosphere. Net downward shortwave radiation increases at both the top of the atmosphere and the surface, indicating a decrease in planetary albedo, likely due to a decrease in low clouds. Heat is absorbed by the climate system and the oceans warm. Wavelet analysis of the AMO time series shows a reddening of the frequency spectrum on the 50-to 100-year timescale, but no evidence of a distinct multidecadal or centennial spectral peak. This latter result is insensitive to both the choice of prior model and the calibration dataset used in the data assimilation algorithm, suggesting that the lack of a distinct multidecadal spectral peak is a robust result.

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Section: H K a Singh Et Al: Amo In The Lmrcontrasting

confidence: 43%

Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

et al. 2018

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“…Surface warming over the North Atlantic during recent decades has been suggested to reflect partly anthropogenic forcing and partly positive AMO transition (Ting et al 2009). By contrast, several recent studies suggest that the *60-year oscillation in the AMO index in the past few decades can be externally forced by aerosols (natural and anthropogenic), volcanic eruptions, and the solar cycle (e.g., Booth et al 2012;Knudsen et al 2014). However, Zhang et al (2013) argued that external forcing might not be the dominant causative factor.…”

Section: Atlantic Multidecadal Oscillation (Amo)-related Sea Level Pamentioning

confidence: 88%

“…Furthermore, SST indices of decadal climate modes (e.g., PDO and AMO) can be affected by anthropogenic warming and other external forcing (e.g., Dong et al 2014;Booth et al 2012;Knudsen et al 2014). Consequently, winds and sea level patterns regressed onto these indices may not represent the effects of pure natural, internal modes.…”

Section: Summary Issues and Challengesmentioning

confidence: 99%

Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes

et al. 2016

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Sea level rise (SLR) can exert significant stress on highly populated coastal societies and low-lying island countries around the world. Because of this, there is huge societal demand for improved decadal predictions and future projections of SLR, particularly on a local scale along coastlines. Regionally, sea level variations can deviate considerably from the global mean due to various geophysical processes. These include changes of ocean circulations, which partially can be attributed to natural, internal modes of variability in the complex Earth's climate system. Anthropogenic influence may also contribute to regional sea level variations. Separating the effects of natural climate modes and anthropogenic forcing, however, remains a challenge and requires identification of the imprint of specific climate modes in observed sea level change patterns. In this paper, we review our current state of knowledge about spatial patterns of sea level variability associated with natural climate modes on interannual-to-multidecadal timescales, with particular focus on decadal-to-multidecadal variability. Relevant climate modes and our current state of understanding their associated sea level patterns and driving mechanisms are elaborated separately for the Pacific, the Indian, the Atlantic, and the Arctic and Southern Oceans. We also discuss the issues, challenges and future outlooks for understanding the regional sea level patterns associated with climate modes. Effects of these internal modes have to be taken into account in order to achieve more reliable near-term predictions and future projections of regional SLR.

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“…Solar activity has been shown to influence key components of the climate system, such as temperature, winds, precipitation, ocean circulation and iceberg transport (e.g. Verschuren et al, 2000;Bond et al, 2001;Hodell et al, 2001;Andrews et al, 2003;Jiang et al, 2005;Sejrup et al, 2010;Martin-Puertas et al, 2012;Knudsen et al, 2014;MoffaSanchez et al, 2014a;Jiang et al, 2015). However, only a few studies have investigated the link between variations in sea-ice proxies from the North Atlantic and solar variability on multidecadal to centennial time scales (e.g.…”

Section: Introductionmentioning

confidence: 99%

Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

Sha

Jiang

Seidenkrantz

et al. 2016

Quaternary Science Reviews

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a b s t r a c tArctic sea ice represents an important component of the climate system, and the present reduction of sea ice in the Arctic is of major concern. Despite its importance, little is known about past changes in sea-ice cover and the underlying forcing mechanisms. Here, we use diatom assemblages from a marine sediment core collected from the West Greenland shelf to reconstruct changes in sea-ice cover over the last millennium. The proxy-based reconstruction demonstrates a generally strong link between changes in sea-ice cover and solar variability during the last millennium. Weaker (or stronger) solar forcing may result in the increase (or decrease) in sea-ice cover west of Greenland. In addition, model simulations show that variations in solar activity not only affect local sea-ice formation, but also control the sea-ice transport from the Arctic Ocean through a sea-iceeoceaneatmosphere feedback mechanism. The role of solar forcing, however, appears to have been more ambiguous during an interval around AD 1500, after the transition from the Medieval Climate Anomaly to the Little Ice Age, likely to be driven by a range of factors.

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Evidence for external forcing of the Atlantic Multidecadal Oscillation since termination of the Little Ice Age

Cited by 126 publications

References 60 publications

Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

Insights into Atlantic multidecadal variability using the Last Millennium Reanalysis framework

Spatial Patterns of Sea Level Variability Associated with Natural Internal Climate Modes

Solar forcing as an important trigger for West Greenland sea-ice variability over the last millennium

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