South Pacific Split Jet, ITCZ shifts, and atmospheric North–South linkages during abrupt climate changes of the last glacial period

Chiang, John C. H.; Lee, Shih‐Yu; Putnam, Aaron E.; Wang, Xiangfeng

doi:10.1016/j.epsl.2014.09.012

Cited by 87 publications

(96 citation statements)

References 70 publications

(94 reference statements)

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“…Alternatively, it has been noted that hemispherically asymmetrical volcanic sulfate loadings induced ITCZ migration away from the hemisphere of the eruption (Ridley et al, 2015;Hwang et al, 2013;Colose et al, 2016), and it is possible that these ITCZ shifts forced wholesale shifts in atmospheric circulation cells. This hypothesised mechanism is broadly consistent with that advanced by Chiang et al (2014), where a forcing at a high northerly latitude subsequently drives southward ITCZ migration, which then affects global atmospheric circulation. Within the context of GS-1, LSE aerosol-related NH cooling could have shifted the ITCZ to the south, thereby expanding the NH polar cell and shifting the NH polar front to the south.…”

Section: The Nature Of the Positive Feedbacksupporting

confidence: 67%

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

2018

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Abstract. The Younger Dryas is considered the archetypal millennial-scale climate change event, and identifying its cause is fundamental for thoroughly understanding climate systematics during deglaciations. However, the mechanisms responsible for its initiation remain elusive, and both of the most researched triggers (a meltwater pulse or a bolide impact) are controversial. Here, we consider the problem from a different perspective and explore a hypothesis that Younger Dryas climate shifts were catalysed by the unusually sulfurrich 12.880 ± 0.040 ka BP eruption of the Laacher See volcano (Germany). We use the most recent chronology for the GISP2 ice core ion dataset from the Greenland ice sheet to identify a large volcanic sulfur spike coincident with both the Laacher See eruption and the onset of Younger Dryasrelated cooling in Greenland (i.e. the most recent abrupt Greenland millennial-scale cooling event, the Greenland Stadial 1, GS-1). Previously published lake sediment and stalagmite records confirm that the eruption's timing was indistinguishable from the onset of cooling across the North Atlantic but that it preceded westerly wind repositioning over central Europe by ∼ 200 years. We suggest that the initial short-lived volcanic sulfate aerosol cooling was amplified by ocean circulation shifts and/or sea ice expansion, gradually cooling the North Atlantic region and incrementally shifting the midlatitude westerlies to the south. The aerosol-related cooling probably only lasted 1-3 years, and the majority of Younger Dryas-related cooling may have been due to the seaice-ocean circulation positive feedback, which was particularly effective during the intermediate ice volume conditions characteristic of ∼ 13 ka BP. We conclude that the large and sulfur-rich Laacher See eruption should be considered a viable trigger for the Younger Dryas. However, future studies should prioritise climate modelling of high-latitude volcanism during deglacial boundary conditions in order to test the hypothesis proposed here.

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Section: The Nature Of the Positive Feedbacksupporting

confidence: 67%

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

2018

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“…Recent work has highlighted the role of high solar irradiance in increasing tropospherestratosphere coupling, extending the seasonal length during which stronger Southern Hemisphere westerly winds are experienced at the surface (Kuroda and Yamazaki, 2010), similar to that observed in the Northern Hemisphere (Ineson et al, 2011). Alternatively, recent modelling work suggests that insolation changes can lead to increased "baroclinicity" (Fogwill et al, 2015) or a "Split Jet" (Chiang et al, 2014), strengthening westerly winds. Further work is required to understand the driving mechanism(s) behind the ∼ 250-year periodicity on global climate.…”

Section: Resultsmentioning

confidence: 99%

A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

et al. 2016

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Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean-atmosphere system of the mid-to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000 cal. years BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.

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“…Evidence from climate-proxy and modeling results shows that during the stadial state, the ITCZ and the SO surface wind field are both shifted south [e.g. Wang et al, 2001;Chiang et al, 2014;Montade et al, 2015, Ljung et al, 2015. Whether changes at low latitudes themselves precede [e.g.…”

Section: Discussionmentioning

confidence: 99%

Southern Ocean deep convection as a driver of Antarctic warming events

Pedro

Martin

Steig

et al. 2016

Geophysical Research Letters

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Simulations with a free‐running coupled climate model show that heat release associated with Southern Ocean deep convection variability can drive centennial‐scale Antarctic temperature variations of up to 2.0°C. The mechanism involves three steps: Preconditioning: heat accumulates at depth in the Southern Ocean; Convection onset: wind and/or sea ice changes tip the buoyantly unstable system into the convective state; and Antarctic warming: fast sea ice‐albedo feedbacks (on annual‐decadal time scales) and slow Southern Ocean frontal and sea surface temperature adjustments to convective heat release (on multidecadal‐century time scales) drive an increase in atmospheric heat and moisture transport toward Antarctica. We discuss the potential of this mechanism to help drive and amplify climate variability as observed in Antarctic ice core records.

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South Pacific Split Jet, ITCZ shifts, and atmospheric North–South linkages during abrupt climate changes of the last glacial period

Cited by 87 publications

References 70 publications

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

Evaluating the link between the sulfur-rich Laacher See volcanic eruption and the Younger Dryas climate anomaly

A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

Southern Ocean deep convection as a driver of Antarctic warming events

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