Was the Arctic Eocene ‘rainforest’ monsoonal? Estimates of seasonal precipitation from early Eocene megafloras from Ellesmere Island, Nunavut

West, Christopher K.; Greenwood, David R.; Basinger, James F.

doi:10.1016/j.epsl.2015.06.036

Cited by 68 publications

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References 108 publications

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“…Licht et al, 2014), and terrestrial fossil records, usually translated via a variety of transfer functions into rainfall seasonality, have to be used (e.g. Shukla et al, 2014;Srivastava et al, 2012;West et al, 2015;Xing et al, 2012). Consequently the individual monsoon systems are hard to differentiate from each other and their origin and development are difficult to document.…”

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confidence: 99%

“…In the context of the geological record metrics incorporating the ratio of wet to dry season rainfall are commonly used as indices of monsoon intensity (e.g. Jacques et al, 2014;Shukla et al, 2014;Spicer et al, 2014;West et al, 2015). However, rainfall patterns are strongly influenced by factors other than those associated with monsoon circulation, particularly at low latitudes such as in southern China.…”

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Asian Eocene monsoons as revealed by leaf architectural signatures

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Yang

Herman

et al. 2016

Earth and Planetary Science Letters

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Asian Eocene monsoons as revealed by leaf architectural signatures

Spicer

Yang

Herman

et al. 2016

Earth and Planetary Science Letters

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“…The Eocene is noted for warm climates that extended forest cover and a diverse fauna that included alligators as far north as northern Ellesmere Island in the Canadian Arctic, and palms into Alaska (Greenwood and Wing 1995;Sunderlin et al 2011;Eberle and Greenwood 2012;West et al 2015). The warm climates of the Eocene are associated with higher than present day levels of atmospheric carbon dioxide (Zachos et al 2008;Smith et al 2010;Royer et al 2012).…”

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confidence: 99%

“…As such, evidence from the Eocene offers a proxy for understanding abiotic and biotic responses to atmospheric processes from organisms to ecosystems. It provides perspective about the hydrology of landscapes, and thus it is of value for predicting these dynamics under future "greenhouse" states (Zachos et al 2008;Huber and Caballero 2011;Royer et al 2012;Krishnan et al 2014;West et al 2015).…”

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Eocene paleontology and geology of western North America

2016

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Western North America preserves a rich record of Eocene life and environments under globally warm climates, and represents an interval where significant coal and other minerals were deposited. The Eocene is of interest to biologists and paleontologists for its record of the appearance and rise to dominance of many plant, insect, and mammal groups now typical of the temperate forests of North America, admixed with groups now well represented in tropical areas or restricted to eastern Asia. This record is also of interest for its potential contribution to our understanding of interactions between climate, the biota, and the ecosystems they occupied, under atmospheric carbon dioxide levels much higher than today. Documentation of the Eocene in western North America offers insights into the effects of future greenhouse climates. A special symposium held at the 2014 Annual Meeting of the Geological Society of America in Vancouver, British Columbia, brought together geologists, paleontologists, and biologists with an interest in these questions. This paper introduces the special issue that includes a selection of papers drawn from that symposium as well as on related topics, spanning the Early to Late Eocene, and geographically from British Columbia to Colorado. Résumé :Un riche registre fossile de la vie et des milieux éocènes est préservé dans l'ouest de l'Amérique du Nord, qui représente un intervalle où d'importants gisements de charbon et d'autres minéraux ont été déposés dans des conditions climatiques planétaires chaudes. L'Éocène présente un intérêt pour les biologistes et les paléontologues en raison du registre qu'il conserve de l'apparition et de la montée en puissance de nombreux groupes de plantes, d'insectes et de mammifères aujourd'hui typiques des forêts tempérées de l'Amérique du Nord, coexistant avec des groupes aujourd'hui bien représentés dans les régions tropicales ou limités à l'est de l'Asie. Ce registre est aussi intéressant pour la contribution qu'il peut apporter à la compréhension des interactions entre le climat, les organismes vivants et les écosystèmes occupés par ces derniers dans des conditions de concentrations atmosphériques de dioxyde de carbone beaucoup plus élevées que les concentrations actuelles. La documentation de l'Éocène dans l'ouest de l'Amérique du Nord permet d'en apprendre davantage sur les effets de climats de serre futurs. Un symposium spécial qui s'est tenu au congrès annuel de 2014 de la Geological Society of America à Vancouver (ColombieBritannique) a réuni des géologues, paléontologues et biologistes intéressés par ces questions. L'article présente le numéro spécial qui comprend une sélection d'articles tirée de ce symposium, ainsi que des articles sur des sujets connexes, couvrant l'Éocène précoce à tardif et, sur le plan géographique, des régions allant de la Colombie-Britannique au Colorado. [Traduit par la Rédaction]

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“…Seasonality, however, is not limited to variable precipitation patterns, but may also be the result 358 of seasonal changes in temperature (e.g., this study) or light regime (e.g., West et al 2015).…”

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Paleoclimate and precipitation seasonality of the Early Eocene McAbee megaflora, Kamloops Group, British Columbia

2016

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whether they represent the same leaf population, (2) assess whether a combined collection yields 24 more precise climate estimates, and (3) reconstruct paleoclimate to assess the character of 25 regional Early Eocene precipitation seasonality. Combined, the two samples yielded 43 dicot leaf 26 morphotypes. Analysis of leaf size distribution using ANOVA showed no difference between the 27 2 samples and they were combined for climate analysis. Climate analysis using leaf 47Early Eocene fossil floras from British Columbia and Washington State, coined the 48Okanagan Highlands, provide a window into the climate of the Early Eocene at mid-latitudes 49(e.g., Smith et al. 2010Smith et al. , 2012 Archibald et al. 2011 Archibald et al. , 2014, where modelling has identified 50 highly seasonal precipitation in the North American continental interior and ever-wet regimes on 51 the west coast and adjoining area of British Columbia (Huber and Goldner 2012 2005; Smith et al. 2010 Smith et al. , 2012. The Brandon University (BU) collection was made by S.B. 101Archibald in the early 2000s. Neither collection was made within a site stratigraphy (J.F. 102Basinger and S.B. Archibald, pers. comm., Sept. 4, 2015). The McAbee main site (Fig. 2) is an 1978; Greenwoood 1992 Greenwoood , 2007 Steart et al. 2002). These same patterns have been seen 141 in Eocene lake sediment leaf assemblages over short stratigraphic distances of <5 m (e.g., 142Greenwood 1991; Smith et al. 2009, 2012). At Falkland, Smith (2011 Smith et al. 2009 Smith et al. , 2012 by changes in annual precipitation amounts over time (Smith et al. 2009(Smith et al. , 2012 or 'ever-wet' climate regime. 167 Materials and Methods 168 Fossil Flora 169The first of the two fossil samples examined in this study was collected by S.B. 170Archibald in the early 2000s and is currently curated at Brandon University (BU). This collection populations. The TRU collection was not available for analysis. 183 Leaf Morphotyping 184The fossil leaves of both the BU and US collections were separated into distinctive in depth taxonomic analysis of the fossil flora (Ellis et al. 2009;Yang et al. 2011 Yang et al. , 2015. 189Important morphological characteristics considered in this process include: leaf size, margin 190 type, apex shape, base shape, and venation. Each morphotype is defined using the character 191 scores of multiple leaves representative of the morphotype, entered into the MLA pro forma. 192Scores of leaf size class for each leaf morphotype were made using both the leaf size classes Yang et al. 2011Yang et al. , 2015. collections was directly measured using the equation: 203(1) Leaf Area = Length × Width × 0.67 (Cain and Castro 1957; Greenwood 1992). 204The leaf area data was analyzed using two one-way ANOVA tests in Microsoft®-Excel to generate an estimate for MAP. In addition, the smallest and largest specimens from each 229 morphotype were directly measured using equation (1) could not be directly measured were excluded from the analysis, although future work will ...

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Was the Arctic Eocene ‘rainforest’ monsoonal? Estimates of seasonal precipitation from early Eocene megafloras from Ellesmere Island, Nunavut

Cited by 68 publications

References 108 publications

Asian Eocene monsoons as revealed by leaf architectural signatures

Asian Eocene monsoons as revealed by leaf architectural signatures

Eocene paleontology and geology of western North America

Paleoclimate and precipitation seasonality of the Early Eocene McAbee megaflora, Kamloops Group, British Columbia

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