Modes of climate variability: Synthesis and review of proxy-based reconstructions through the Holocene

Hernández, Armand; Martín-Puertas, Celia; Moffa-Sánchez, Paola; Moreno-Chamarro, Eduardo; Ortega, Pablo; Blockley, Simon; Cobb, Kim M.; Comas-Bru, Laia; Giralt, Santiago; Goosse, Hugues; Luterbacher, Jürg; Martrat, Belén; Muscheler, Raimund; Parnell, Andrew; Pla-Rabés, Sergi; Sjolte, Jesper; Scaife, Adam A.; Swingedouw, Didier; Wise, Erika K.; Xu, Guobao

doi:10.1016/j.earscirev.2020.103286

Cited by 54 publications

(35 citation statements)

References 457 publications

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“…Anomalous conditions from ca. 5.5-4.5 ka could relate to either external volcanic or solar forcing (Hernández et al 2020;Helama et al 2021) or internal variability, such as in the North Atlantic (Oppo et al 2003;Thornalley et al 2009). The interference with orbital and ice volume trends differs, however, from that observed during abrupt Pleistocene events associated with North Atlantic overturning such as the Younger Dryas (YD) because the east-west gradient in North America decreased after the YD and increased after the anomalous millennium from 5.5-4.5 ka (Fig.…”

Section: Discussionmentioning

confidence: 99%

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients 

Shuman

2021

Preprint

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Holocene records reveal a constantly varying hydroclimate characterized by responses to precession punctuated by decadal-to-centennial ‘megadroughts’ and rapid state shifts. How such changes relate across space and time can reveal the underlying dynamics and how external forcing, intrinsic variability, and various feedbacks interact to alter societally critical water supplies. Here, Holocene water-level changes were examined in two groups of North American lakes to systematically characterize millennial-scale hydroclimate variability and potential large-scale state changes. The records constrain changes at the ends of the large hydroclimate gradient between the semi-arid Rocky Mountains and the humid Atlantic coast. Geophysical surveys and 40 radiocarbon-dated sediment cores provide direct measures of past shoreline positions from the 12 lakes. None exhibited stable Holocene water levels. Together they show a steep east-west gradient from 9-5.5 ka and again from 4.5-2.1 ka. The gradient was unusually weak from 11-9, 5.5-4.5, and after 2.1 ka when Rocky Mountain lakes reached their maxima. Consistent with interconnected atmospheric circulation and land surface energy budget changes, the gradient steepness correlates with mid-continental summer temperature changes (r = 0.73) with a cool, wet mid-continent associated with a weak hydroclimatic gradient, such as during the anomalous mid-Holocene fluctuation from 5.5-4.5 ka. The millennial-scale variability interacted with long-term trends to rapidly increase effective moisture in the west at 5.5 ka, potentially as part of state shifts extending to the Sahel. The interconnected changes underscore the possibility that poorly diagnosed centennial-to-millennial variability could accelerate some Holocene trends to produce abrupt shifts without requiring strong threshold effects.

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Section: Discussionmentioning

confidence: 99%

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients 

Shuman

2021

Preprint

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“…Instrumental temperature records are, at best, limited to about the past 200 years, and are available for only a few European locations [1][2][3]. Various proxies have been used to extend temperature records back throughout the Holocene (the past 12,000 years), based on information from a range of different sources including tree rings, ice cores, spleothems (stalagmites and stalactites found in caves), corals, marine sediments, lake sediments and historical documents [4]. Proxy temperature records have been reported at local, regional, continental, hemispheric and global scales [5,6].…”

Section: Literature Reviewmentioning

confidence: 99%

“…The significance of decadal oscillations throughout the Holocene has been reviewed [4] including the (El Nino Southern Oscillation) ENSO, (Pacific Decadal Variability) PDV, NAO, the Southern Annular Mode (SAM), Atlantic Multi-decadal Variability (AMV), and the Indian Ocean Dipole (IOD). In citing Mann (2020), this report stated that that "the debate still rages" concerning decadal oscillations.…”

Section: Figurementioning

confidence: 99%

“…Another study showed variations in NAO reconstructions for the past millennium using 48 proxy records [81]. The significance of decadal oscillations throughout the Holocene has been reviewed [4], including ENSO, PDV, AMV, the NAO, the SAM and the IOD. Temperature changes in Maine USA have been attributed to variations in the NAO and AMO over past 900 years [82].…”

Section: Decadal Scale Periodicitiesmentioning

confidence: 99%

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Using Oscillatory Processes in Northern Hemisphere Proxy Temperature Records to Forecast Industrial-era Temperatures

Abbot¹

2021

EARTH

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The validity and interpretation of differing representations of proxy temperature profiles from the past 2,000 years for the northern hemisphere remains controversial. One perspective of temperatures over the past 1,000 years embodies a major oscillation with a peak corresponding with the Medieval Warm Period (MWP), a trough representing the Little Ice Age (LIA) and subsequent increasing temperatures to the present. An alternate temperature perspective, known as the "hockey stick" exhibits a slow long-term cooling trend downward from about 1000 AD to about 1900 AD, followed by relatively rapid warming in the 20th century and is a prominent feature in describing the apparent climate crisis. The present study, using spectral analysis, shows that both types of profile have a dominant millennial oscillation and a set of lower power centennial and decadal oscillations. The key difference in determination of development of the proxy temperature profile into either a hockey stick or MWP_LIA cycle is the phase alignments of centennial and decadal oscillations with respect to the millennial oscillation. In both cases, the resultant sine waves from spectral analysis up to 1880 AD can be used to train a an artificial neural network using oscillatory data corresponding to the pre-industrial era, then forecasting temperatures into the 20 th century, enabling an estimation of natural and anthropogenic contributions to recent warming. The limitations of highly complex general circulation models that do not to adequately incorporate oscillatory patterns in temperatures may be a compelling reason to promote more extensive use of forecasting with established machine learning techniques such as ANNs.

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“…On decadal to millennial time scales, MoV partly control the link between atmospheric and oceanic dynamics (Hernández et al, 2020), which is also sensitive to solar changes (Meehl et al, 2008). Studies arguing for a solar impact on MoV invoke a top-down mechanism related to the ultraviolet irradiance pattern (Gray et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

External forcing mechanisms controlling the North Atlantic coastal upwelling regime during the mid-Holocene

Hernández

Cachão

Sousa

et al. 2020

Geology

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Nearshore upwelling along the eastern North Atlantic margin regulates regional marine ecosystem productivity and thus impacts blue economies. While most global circulation models show an increase in the intensity and duration of seasonal upwelling at high latitudes under future human-induced warmer conditions, projections for the North Atlantic are still ambiguous. Due to the low temporal resolution of coastal upwelling records, little is known about the impact of natural forcing mechanisms on upwelling variability. Here, we present a microfossil-based proxy record and modeling simulations for the warmest period of the Holocene (ca. 9–5 ka) to estimate the contribution of the natural variability in North Atlantic upwelling via atmospheric and oceanic dynamics. We found that more frequent high-pressure conditions in the eastern North Atlantic associated with solar activity and orbital parameters triggered upwelling variations at multidecadal and millennial time scales, respectively. Our new findings offer insights into the role of external forcing mechanisms in upwelling changes before the Anthropocene, which must be considered when producing future projections of midlatitude upwelling activity.

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Modes of climate variability: Synthesis and review of proxy-based reconstructions through the Holocene

Cited by 54 publications

References 457 publications

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients

Using Oscillatory Processes in Northern Hemisphere Proxy Temperature Records to Forecast Industrial-era Temperatures

External forcing mechanisms controlling the North Atlantic coastal upwelling regime during the mid-Holocene

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Modes of climate variability: Synthesis and review of proxy-based reconstructions through the Holocene

Cited by 54 publications

References 457 publications

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients&nbsp;

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients&nbsp;

Using Oscillatory Processes in Northern Hemisphere Proxy Temperature Records to Forecast Industrial-era Temperatures

External forcing mechanisms controlling the North Atlantic coastal upwelling regime during the mid-Holocene

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Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients

Millennial Variations and a Mid-Holocene Step Change in Northern Mid-latitude Moisture Gradients