scholarly journals Orbitally Paced Carbon and Deep-Sea Temperature Changes at the Peak of the Early Eocene Climatic Optimum

2018 ◽  
Vol 33 (10) ◽  
pp. 1050-1065 ◽  
Author(s):  
Vittoria Lauretano ◽  
James C. Zachos ◽  
Lucas J. Lourens
Keyword(s):  
Deep Sea ◽  
Early Eocene ◽  
Sea Temperature ◽  
Temperature Changes ◽  
Early Eocene Climatic Optimum ◽  
Climatic Optimum

scholarly journals Temperature seasonality in the North American continental interior during the early Eocene climatic optimum

2018 ◽  
Author(s):  
Ethan G. Hyland ◽  
Katharine W. Huntington ◽  
Nathan D. Sheldon ◽  
Tammo Reichgelt
Keyword(s):  
Climate Model ◽  
Regional Climate ◽  
Early Eocene ◽  
Early Eocene Climatic Optimum ◽  
The North ◽  
Annual Range ◽  
Climatic Optimum ◽  
Temperature Records ◽  
Model Ensembles ◽  
Continental Interior

Abstract. Paleogene greenhouse climate equability has long been a paradox in paleoclimate research. However, recent developments in proxy and modeling methods have suggested that strong seasonality may be a feature of at least some greenhouse periods. Here we present the first multi-proxy record of seasonal temperatures during the Paleogene from paleofloras, paleosol geochemistry, and carbonate clumped isotope thermometry in the Green River Basin (Wyoming, USA). These combined temperature records allow for the reconstruction of past seasonality in the continental interior, which shows that temperatures were warmer in all seasons during the peak early Eocene climatic optimum and that the mean annual range of temperature was high, similar to the modern value (~ 26 °C). Proxy data and downscaled Eocene regional climate model results suggest amplified seasonality during greenhouse events. Increased seasonality reconstructed for the early Eocene is similar in scope to the higher seasonal range predicted by downscaled climate model ensembles for future high-CO2 emissions scenarios. Overall, these data and model comparisons have substantial implications for understanding greenhouse climates in general, and may be important for predicting future seasonal climate regimes and their impacts in continental regions.

Exploring the possible meridional temperature gradient of Early Eocene Climatic Optimum with an energy balance model

2021 ◽  
Author(s):  
Fanni Dora Kelemen ◽  
Bodo Ahrens
Keyword(s):  
Energy Balance ◽  
Temperature Gradient ◽  
Entropy Production ◽  
Maximum Entropy ◽  
Early Eocene ◽  
Meridional Temperature Gradient ◽  
Proxy Data ◽  
Maximum Entropy Production ◽  
Early Eocene Climatic Optimum ◽  
Climatic Optimum

<p>Early Eocene Climatic Optimum (EECO, ~53-51 million years) is one of the past warm periods, associated with high CO<sub>2</sub> concentrations (~900-2500 ppmv), which can serve as an analogue for our possible future, high C0<sub>2 </sub>climate. One notable feature of this hothouse climate state is the weaker meridional temperature gradient relative to pre-industrial values. This have been confirmed by both proxies and models, but the extent of the temperature gradient still requires more research. Models are challenged to reproduce the stronger than present day polar amplification signal, and it is also shown that high latitude proxy data are often influenced by seasonal bias. Thus, there is an uncertainty regarding both the observed and modelled meridional gradient and the mentioned issues complicate also the comparison between modeled and proxy data.</p><p>In our work we aim to investigate the EECO period with a simple energy balance box model and apply the maximum entropy production principle to explore the possible scenarios of meridional temperature gradients. We find that the maximum entropy production principle could be beneficial in the paleoclimate context since it has the utility to give an accurate prediction for non-equilibrium systems with the minimal amount of information. We also assess the heat transport signaled by proxy data and by state-of-the-art model outputs in accordance to our theoretical constrains based on the idealized test case.</p>

scholarly journals Fossil palm beetles refine upland winter temperatures in the Early Eocene Climatic Optimum

2014 ◽  
Vol 111 (22) ◽  
pp. 8095-8100 ◽  
Author(s):  
S. B. Archibald ◽  
G. E. Morse ◽  
D. R. Greenwood ◽  
R. W. Mathewes
Keyword(s):  
Early Eocene ◽  
Early Eocene Climatic Optimum ◽  
Winter Temperatures ◽  
Climatic Optimum

scholarly journals Climate and ecology in the Rocky Mountain interior after the early Eocene Climatic Optimum

2021 ◽  
Vol 17 (6) ◽  
pp. 2515-2536
Author(s):  
Rebekah A. Stein ◽  
Nathan D. Sheldon ◽  
Sarah E. Allen ◽  
Michael E. Smith ◽  
Rebecca M. Dzombak ◽  
...  
Keyword(s):  
Climate Change ◽  
Sedimentary Facies ◽  
Parent Material ◽  
Early Eocene ◽  
Green River ◽  
Early Eocene Climatic Optimum ◽  
Carbon Burial ◽  
Organic Carbon Burial ◽  
Climatic Optimum ◽  
Bridger Formation

Abstract. As atmospheric carbon dioxide (CO2) and temperatures increase with modern climate change, ancient hothouse periods become a focal point for understanding ecosystem function under similar conditions. The early Eocene exhibited high temperatures, high CO2 levels, and similar tectonic plate configuration as today, so it has been invoked as an analog to modern climate change. During the early Eocene, the greater Green River Basin (GGRB) of southwestern Wyoming was covered by an ancient hypersaline lake (Lake Gosiute; Green River Formation) and associated fluvial and floodplain systems (Wasatch and Bridger formations). The volcaniclastic Bridger Formation was deposited by an inland delta that drained from the northwest into freshwater Lake Gosiute and is known for its vast paleontological assemblages. Using this well-preserved basin deposited during a period of tectonic and paleoclimatic interest, we employ multiple proxies to study trends in provenance, parent material, weathering, and climate throughout 1 million years. The Blue Rim escarpment exposes approximately 100 m of the lower Bridger Formation, which includes plant and mammal fossils, solitary paleosol profiles, and organic remains suitable for geochemical analyses, as well as ash beds and volcaniclastic sandstone beds suitable for radioisotopic dating. New 40Ar / 39Ar ages from the middle and top of the Blue Rim escarpment constrain the age of its strata to ∼ 49.5–48.5 Myr ago during the “falling limb” of the early Eocene Climatic Optimum. We used several geochemical tools to study provenance and parent material in both the paleosols and the associated sediments and found no change in sediment input source despite significant variation in sedimentary facies and organic carbon burial. We also reconstructed environmental conditions, including temperature, precipitation (both from paleosols), and the isotopic composition of atmospheric CO2 from plants found in the floral assemblages. Results from paleosol-based reconstructions were compared to semi-co-temporal reconstructions made using leaf physiognomic techniques and marine proxies. The paleosol-based reconstructions (near the base of the section) of precipitation (608–1167 mm yr−1) and temperature (10.4 to 12.0 ∘C) were within error of, although lower than, those based on floral assemblages, which were stratigraphically higher in the section and represented a highly preserved event later in time. Geochemistry and detrital feldspar geochronology indicate a consistent provenance for Blue Rim sediments, sourcing predominantly from the Idaho paleoriver, which drained the active Challis volcanic field. Thus, because there was neither significant climatic change nor significant provenance change, variation in sedimentary facies and organic carbon burial likely reflected localized geomorphic controls and the relative height of the water table. The ecosystem can be characterized as a wet, subtropical-like forest (i.e., paratropical) throughout the interval based upon the floral humidity province and Holdridge life zone schemes. Given the mid-paleolatitude position of the Blue Rim escarpment, those results are consistent with marine proxies that indicate that globally warm climatic conditions continued beyond the peak warm conditions of the early Eocene Climatic Optimum. The reconstructed atmospheric δ13C value (−5.3 ‰ to −5.8 ‰) closely matches the independently reconstructed value from marine microfossils (−5.4 ‰), which provides confidence in this reconstruction. Likewise, the isotopic composition reconstructed matches the mantle most closely (−5.4 ‰), agreeing with other postulations that warming was maintained by volcanic outgassing rather than a much more isotopically depleted source, such as methane hydrates.

scholarly journals Frequency, magnitude and character of hyperthermal events at the onset of the Early Eocene Climatic Optimum

2015 ◽  
Vol 11 (3) ◽  
pp. 1795-1820 ◽  
Author(s):  
V. Lauretano ◽  
K. Littler ◽  
M. Polling ◽  
J. C. Zachos ◽  
L. J. Lourens
Keyword(s):  
Water Mass ◽  
Intermediate Water ◽  
Early Eocene ◽  
Walvis Ridge ◽  
Early Eocene Climatic Optimum ◽  
Thermal Maximum ◽  
Carbon And Oxygen Isotope ◽  
Hyperthermal Events ◽  
Climatic Optimum ◽  
Δ13c And Δ18o

Abstract. Recent studies have shown that the Early Eocene Climatic Optimum (EECO) was preceded by a series of short-lived global warming events, known as hyperthermals. Here we present high-resolution benthic stable carbon and oxygen isotope records from ODP Sites 1262 and 1263 (Walvis Ridge, SE Atlantic) between ∼54 and ∼52 million years ago, tightly constraining the character, timing, and magnitude of six prominent hyperthermal events. These events, that include Eocene Thermal Maximum (ETM) 2 and 3, are studied in relation to orbital forcing and long-term trends. Our findings reveal an almost linear relationship between δ13C and δ18O for all these hyperthermals, indicating that the eccentricity-paced co-variance between extreme perturbations in the exogenic carbon pool and deep-sea temperatures persisted during the onset of the EECO, in accord with previous observations for the Paleocene Eocene Thermal Maximum (PETM) and ETM2. The covariance of δ13C and δ18O during H2 and I2, which are the second pulses of the "paired" hyperthermal events ETM2-H2 and I1-I2, deviates with respect to the other events. This could relate to a relatively higher contribution of an isotopically heavier source of carbon, such as peat or permafrost, and/or to climate feedbacks/local changes in circulation. Finally, the δ18O records of the two sites show a systematic offset with on average 0.2‰ heavier values for the shallower Site 1263, which we link to a slightly heavier (e.g. more saline) isotope composition of the intermediate water mass reaching the northeastern flank of the Walvis Ridge compared to that of the deeper northwestern water mass at Site 1262.

scholarly journals Global mean surface temperature and climate sensitivity of the early Eocene Climatic Optimum (EECO), Paleocene–Eocene Thermal Maximum (PETM), and latest Paleocene

2020 ◽  
Vol 16 (5) ◽  
pp. 1953-1968 ◽  
Author(s):  
Gordon N. Inglis ◽  
Fran Bragg ◽  
Natalie J. Burls ◽  
Margot J. Cramwinckel ◽  
David Evans ◽  
...  
Keyword(s):  
Climate Change ◽  
Surface Temperature ◽  
Climate Sensitivity ◽  
Future Climate Change ◽  
Early Eocene ◽  
Early Eocene Climatic Optimum ◽  
Thermal Maximum ◽  
Global Mean Surface Temperature ◽  
Climatic Optimum ◽  
Global Mean

Abstract. Accurate estimates of past global mean surface temperature (GMST) help to contextualise future climate change and are required to estimate the sensitivity of the climate system to CO2 forcing through Earth's history. Previous GMST estimates for the latest Paleocene and early Eocene (∼57 to 48 million years ago) span a wide range (∼9 to 23 ∘C higher than pre-industrial) and prevent an accurate assessment of climate sensitivity during this extreme greenhouse climate interval. Using the most recent data compilations, we employ a multi-method experimental framework to calculate GMST during the three DeepMIP target intervals: (1) the latest Paleocene (∼57 Ma), (2) the Paleocene–Eocene Thermal Maximum (PETM; 56 Ma), and (3) the early Eocene Climatic Optimum (EECO; 53.3 to 49.1 Ma). Using six different methodologies, we find that the average GMST estimate (66 % confidence) during the latest Paleocene, PETM, and EECO was 26.3 ∘C (22.3 to 28.3 ∘C), 31.6 ∘C (27.2 to 34.5 ∘C), and 27.0 ∘C (23.2 to 29.7 ∘C), respectively. GMST estimates from the EECO are ∼10 to 16 ∘C warmer than pre-industrial, higher than the estimate given by the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (9 to 14 ∘C higher than pre-industrial). Leveraging the large “signal” associated with these extreme warm climates, we combine estimates of GMST and CO2 from the latest Paleocene, PETM, and EECO to calculate gross estimates of the average climate sensitivity between the early Paleogene and today. We demonstrate that “bulk” equilibrium climate sensitivity (ECS; 66 % confidence) during the latest Paleocene, PETM, and EECO is 4.5 ∘C (2.4 to 6.8 ∘C), 3.6 ∘C (2.3 to 4.7 ∘C), and 3.1 ∘C (1.8 to 4.4 ∘C) per doubling of CO2. These values are generally similar to those assessed by the IPCC (1.5 to 4.5 ∘C per doubling CO2) but appear incompatible with low ECS values (<1.5 per doubling CO2).

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