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Mid-Pliocene El Niño/Southern Oscillation suppressed by Pacific intertropical convergence zone shift

Pontes, Gabriel M. ; Taschetto, Andréa S. ; Sen Gupta, Alex ; [et al.]

Springer Science and Business Media LLC ; 2022

In: Nature Geoscience Vol. 15, No. 9 ( 2022-09), p. 726-734

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In: Nature Geoscience, Springer Science and Business Media LLC, Vol. 15, No. 9 ( 2022-09), p. 726-734

Type of Medium: Online Resource

ISSN: 1752-0894 , 1752-0908

URL: Article

DOI: 10.1038/s41561-022-00999-y

Language: English

Publisher: Springer Science and Business Media LLC

Publication Date: 2022

detail.hit.zdb_id: 2396648-8

detail.hit.zdb_id: 2405323-5

SSG: 16,13

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The Pliocene Model Intercomparison Project Phase 2: large-scale climate features and climate sensitivity

Haywood, Alan M. ; Tindall, Julia C. ; Dowsett, Harry J. ; [et al.]

Copernicus GmbH ; 2020

In: Climate of the Past Vol. 16, No. 6 ( 2020-11-04), p. 2095-2123

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In: Climate of the Past, Copernicus GmbH, Vol. 16, No. 6 ( 2020-11-04), p. 2095-2123

Abstract: Abstract. The Pliocene epoch has great potential to improve our understanding of the long-term climatic and environmental consequences of an atmospheric CO2 concentration near ∼400 parts per million by volume. Here we present the large-scale features of Pliocene climate as simulated by a new ensemble of climate models of varying complexity and spatial resolution based on new reconstructions of boundary conditions (the Pliocene Model Intercomparison Project Phase 2; PlioMIP2). As a global annual average, modelled surface air temperatures increase by between 1.7 and 5.2 ∘C relative to the pre-industrial era with a multi-model mean value of 3.2 ∘C. Annual mean total precipitation rates increase by 7 % (range: 2 %–13 %). On average, surface air temperature (SAT) increases by 4.3 ∘C over land and 2.8 ∘C over the oceans. There is a clear pattern of polar amplification with warming polewards of 60∘ N and 60∘ S exceeding the global mean warming by a factor of 2.3. In the Atlantic and Pacific oceans, meridional temperature gradients are reduced, while tropical zonal gradients remain largely unchanged. There is a statistically significant relationship between a model's climate response associated with a doubling in CO2 (equilibrium climate sensitivity; ECS) and its simulated Pliocene surface temperature response. The mean ensemble Earth system response to a doubling of CO2 (including ice sheet feedbacks) is 67 % greater than ECS; this is larger than the increase of 47 % obtained from the PlioMIP1 ensemble. Proxy-derived estimates of Pliocene sea surface temperatures are used to assess model estimates of ECS and give an ECS range of 2.6–4.8 ∘C. This result is in general accord with the ECS range presented by previous Intergovernmental Panel on Climate Change (IPCC) Assessment Reports.

Type of Medium: Online Resource

ISSN: 1814-9332

URL: Article

DOI: 10.5194/cp-16-2095-2020

DOI: 10.5194/cp-16-2095-2020-supplement

Language: English

Publisher: Copernicus GmbH

Publication Date: 2020

detail.hit.zdb_id: 2217985-9

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Reduced El Niño variability in the mid-Pliocene according to the PlioMIP2 ensemble

Oldeman, Arthur M. ; Baatsen, Michiel L. J. ; von der Heydt, Anna S. ; [et al.]

Copernicus GmbH ; 2021

In: Climate of the Past Vol. 17, No. 6 ( 2021-12-01), p. 2427-2450

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In: Climate of the Past, Copernicus GmbH, Vol. 17, No. 6 ( 2021-12-01), p. 2427-2450

Abstract: Abstract. The mid-Pliocene warm period (3.264–3.025 Ma) is the most recent geological period during which atmospheric CO2 levels were similar to recent historical values (∼400 ppm). Several proxy reconstructions for the mid-Pliocene show highly reduced zonal sea surface temperature (SST) gradients in the tropical Pacific Ocean, indicating an El Niño-like mean state. However, past modelling studies do not show these highly reduced gradients. Efforts to understand mid-Pliocene climate dynamics have led to the Pliocene Model Intercomparison Project (PlioMIP). Results from the first phase (PlioMIP1) showed clear El Niño variability (albeit significantly reduced) and did not show the greatly reduced time-mean zonal SST gradient suggested by some of the proxies. In this work, we study El Niño–Southern Oscillation (ENSO) variability in the PlioMIP2 ensemble, which consists of additional global coupled climate models and updated boundary conditions compared to PlioMIP1. We quantify ENSO amplitude, period, spatial structure and “flavour”, as well as the tropical Pacific annual mean state in mid-Pliocene and pre-industrial simulations. Results show a reduced ENSO amplitude in the model-ensemble mean (−24 %) with respect to the pre-industrial, with 15 out of 17 individual models showing such a reduction. Furthermore, the spectral power of this variability considerably decreases in the 3–4-year band. The spatial structure of the dominant empirical orthogonal function shows no particular change in the patterns of tropical Pacific variability in the model-ensemble mean, compared to the pre-industrial. Although the time-mean zonal SST gradient in the equatorial Pacific decreases for 14 out of 17 models (0.2 ∘C reduction in the ensemble mean), there does not seem to be a correlation with the decrease in ENSO amplitude. The models showing the most “El Niño-like” mean state changes show a similar ENSO amplitude to that in the pre-industrial reference, while models showing more “La Niña-like” mean state changes generally show a large reduction in ENSO variability. The PlioMIP2 results show a reasonable agreement with both time-mean proxies indicating a reduced zonal SST gradient and reconstructions indicating a reduced, or similar, ENSO variability.

Type of Medium: Online Resource

ISSN: 1814-9332

URL: Article

DOI: 10.5194/cp-17-2427-2021

DOI: 10.5194/cp-17-2427-2021-supplement

Language: English

Publisher: Copernicus GmbH

Publication Date: 2021

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Evaluation of Arctic warming in mid-Pliocene climate simulations

de Nooijer, Wesley ; Zhang, Qiong ; Li, Qiang ; [et al.]

Copernicus GmbH ; 2020

In: Climate of the Past Vol. 16, No. 6 ( 2020-11-23), p. 2325-2341

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In: Climate of the Past, Copernicus GmbH, Vol. 16, No. 6 ( 2020-11-23), p. 2325-2341

Abstract: Abstract. Palaeoclimate simulations improve our understanding of the climate, inform us about the performance of climate models in a different climate scenario, and help to identify robust features of the climate system. Here, we analyse Arctic warming in an ensemble of 16 simulations of the mid-Pliocene Warm Period (mPWP), derived from the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2). The PlioMIP2 ensemble simulates Arctic (60–90∘ N) annual mean surface air temperature (SAT) increases of 3.7 to 11.6 ∘C compared to the pre-industrial period, with a multi-model mean (MMM) increase of 7.2 ∘C. The Arctic warming amplification ratio relative to global SAT anomalies in the ensemble ranges from 1.8 to 3.1 (MMM is 2.3). Sea ice extent anomalies range from −3.0 to -10.4×106 km2, with a MMM anomaly of -5.6×106 km2, which constitutes a decrease of 53 % compared to the pre-industrial period. The majority (11 out of 16) of models simulate summer sea-ice-free conditions (≤1×106 km2) in their mPWP simulation. The ensemble tends to underestimate SAT in the Arctic when compared to available reconstructions, although the degree of underestimation varies strongly between the simulations. The simulations with the highest Arctic SAT anomalies tend to match the proxy dataset in its current form better. The ensemble shows some agreement with reconstructions of sea ice, particularly with regard to seasonal sea ice. Large uncertainties limit the confidence that can be placed in the findings and the compatibility of the different proxy datasets. We show that while reducing uncertainties in the reconstructions could decrease the SAT data–model discord substantially, further improvements are likely to be found in enhanced boundary conditions or model physics. Lastly, we compare the Arctic warming in the mPWP to projections of future Arctic warming and find that the PlioMIP2 ensemble simulates greater Arctic amplification than CMIP5 future climate simulations and an increase instead of a decrease in Atlantic Meridional Overturning Circulation (AMOC) strength compared to pre-industrial period. The results highlight the importance of slow feedbacks in equilibrium climate simulations, and that caution must be taken when using simulations of the mPWP as an analogue for future climate change.

Type of Medium: Online Resource

ISSN: 1814-9332

URL: Article

DOI: 10.5194/cp-16-2325-2020

DOI: 10.5194/cp-16-2325-2020-supplement

Language: English

Publisher: Copernicus GmbH

Publication Date: 2020

detail.hit.zdb_id: 2217985-9

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Mid-Pliocene West African Monsoon rainfall as simulated in the PlioMIP2 ensemble

Berntell, Ellen ; Zhang, Qiong ; Li, Qiang ; [et al.]

Copernicus GmbH ; 2021

In: Climate of the Past Vol. 17, No. 4 ( 2021-08-27), p. 1777-1794

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In: Climate of the Past, Copernicus GmbH, Vol. 17, No. 4 ( 2021-08-27), p. 1777-1794

Abstract: Abstract. The mid-Pliocene warm period (mPWP; ∼3.2 million years ago) is seen as the most recent time period characterized by a warm climate state, with similar to modern geography and ∼400 ppmv atmospheric CO2 concentration, and is therefore often considered an interesting analogue for near-future climate projections. Paleoenvironmental reconstructions indicate higher surface temperatures, decreasing tropical deserts, and a more humid climate in West Africa characterized by a strengthened West African Monsoon (WAM). Using model results from the second phase of the Pliocene Modelling Intercomparison Project (PlioMIP2) ensemble, we analyse changes of the WAM rainfall during the mPWP by comparing them with the control simulations for the pre-industrial period. The ensemble shows a robust increase in the summer rainfall over West Africa and the Sahara region, with an average increase of 2.5 mm/d, contrasted by a rainfall decrease over the equatorial Atlantic. An anomalous warming of the Sahara and deepening of the Saharan Heat Low, seen in 〉90 % of the models, leads to a strengthening of the WAM and an increased monsoonal flow into the continent. A similar warming of the Sahara is seen in future projections using both phase 3 and 5 of the Coupled Model Intercomparison Project (CMIP3 and CMIP5). Though previous studies of future projections indicate a west–east drying–wetting contrast over the Sahel, PlioMIP2 simulations indicate a uniform rainfall increase in that region in warm climates characterized by increasing greenhouse gas forcing. We note that this effect will further depend on the long-term response of the vegetation to the CO2 forcing.

Type of Medium: Online Resource

ISSN: 1814-9332

URL: Article

DOI: 10.5194/cp-17-1777-2021

Language: English

Publisher: Copernicus GmbH

Publication Date: 2021

detail.hit.zdb_id: 2217985-9

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Highly restricted near‐surface permafrost extent during the mid-Pliocene warm period

Guo, Donglin ; Wang, Huijun ; Romanovsky, Vladimir E. ; [et al.]

Proceedings of the National Academy of Sciences ; 2023

In: Proceedings of the National Academy of Sciences Vol. 120, No. 36 ( 2023-09-05)

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In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 120, No. 36 ( 2023-09-05)

Abstract: Accurate understanding of permafrost dynamics is critical for evaluating and mitigating impacts that may arise as permafrost degrades in the future; however, existing projections have large uncertainties. Studies of how permafrost responded historically during Earth’s past warm periods are helpful in exploring potential future permafrost behavior and to evaluate the uncertainty of future permafrost change projections. Here, we combine a surface frost index model with outputs from the second phase of the Pliocene Model Intercomparison Project to simulate the near‐surface (~3 to 4 m depth) permafrost state in the Northern Hemisphere during the mid-Pliocene warm period (mPWP, ~3.264 to 3.025 Ma). This period shares similarities with the projected future climate. Constrained by proxy-based surface air temperature records, our simulations demonstrate that near‐surface permafrost was highly spatially restricted during the mPWP and was 93 ± 3% smaller than the preindustrial extent. Near‐surface permafrost was present only in the eastern Siberian uplands, Canadian high Arctic Archipelago, and northernmost Greenland. The simulations are similar to near‐surface permafrost changes projected for the end of this century under the SSP5-8.5 scenario and provide a perspective on the potential permafrost behavior that may be expected in a warmer world.

Type of Medium: Online Resource

ISSN: 0027-8424 , 1091-6490

URL: Article

DOI: 10.1073/pnas.2301954120

RVK:

TA 1000

RVK:

WA 15000

Language: English

Publisher: Proceedings of the National Academy of Sciences

Publication Date: 2023

detail.hit.zdb_id: 209104-5

detail.hit.zdb_id: 1461794-8

SSG: 11

SSG: 12

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Past terrestrial hydroclimate sensitivity controlled by Earth system feedbacks

Feng, Ran ; Bhattacharya, Tripti ; Otto-Bliesner, Bette L. ; [et al.]

Springer Science and Business Media LLC ; 2022

In: Nature Communications Vol. 13, No. 1 ( 2022-03-14)

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In: Nature Communications, Springer Science and Business Media LLC, Vol. 13, No. 1 ( 2022-03-14)

Abstract: Despite tectonic conditions and atmospheric CO 2 levels ( pCO 2 ) similar to those of present-day, geological reconstructions from the mid-Pliocene (3.3-3.0 Ma) document high lake levels in the Sahel and mesic conditions in subtropical Eurasia, suggesting drastic reorganizations of subtropical terrestrial hydroclimate during this interval. Here, using a compilation of proxy data and multi-model paleoclimate simulations, we show that the mid-Pliocene hydroclimate state is not driven by direct CO 2 radiative forcing but by a loss of northern high-latitude ice sheets and continental greening. These ice sheet and vegetation changes are long-term Earth system feedbacks to elevated pCO 2 . Further, the moist conditions in the Sahel and subtropical Eurasia during the mid-Pliocene are a product of enhanced tropospheric humidity and a stationary wave response to the surface warming pattern, which varies strongly with land cover changes. These findings highlight the potential for amplified terrestrial hydroclimate responses over long timescales to a sustained CO 2 forcing.

Type of Medium: Online Resource

ISSN: 2041-1723

URL: Article

DOI: 10.1038/s41467-022-28814-7

Language: English

Publisher: Springer Science and Business Media LLC

Publication Date: 2022

detail.hit.zdb_id: 2553671-0

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Mid-Pliocene Atlantic Meridional Overturning Circulation simulated in PlioMIP2

Zhang, Zhongshi ; Li, Xiangyu ; Guo, Chuncheng ; [et al.]

Copernicus GmbH ; 2021

In: Climate of the Past Vol. 17, No. 1 ( 2021-02-25), p. 529-543

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In: Climate of the Past, Copernicus GmbH, Vol. 17, No. 1 ( 2021-02-25), p. 529-543

Abstract: Abstract. In the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2), coupled climate models have been used to simulate an interglacial climate during the mid-Piacenzian warm period (mPWP; 3.264 to 3.025 Ma). Here, we compare the Atlantic Meridional Overturning Circulation (AMOC), poleward ocean heat transport and sea surface warming in the Atlantic simulated with these models. In PlioMIP2, all models simulate an intensified mid-Pliocene AMOC. However, there is no consistent response in the simulated Atlantic ocean heat transport nor in the depth of the Atlantic overturning cell. The models show a large spread in the simulated AMOC maximum, the Atlantic ocean heat transport and the surface warming in the North Atlantic. Although a few models simulate a surface warming of ∼ 8–12 ∘C in the North Atlantic, similar to the reconstruction from Pliocene Research, Interpretation and Synoptic Mapping (PRISM) version 4, most models appear to underestimate this warming. The large model spread and model–data discrepancies in the PlioMIP2 ensemble do not support the hypothesis that an intensification of the AMOC, together with an increase in northward ocean heat transport, is the dominant mechanism for the mid-Pliocene warm climate over the North Atlantic.

Type of Medium: Online Resource

ISSN: 1814-9332

URL: Article

DOI: 10.5194/cp-17-529-2021

Language: English

Publisher: Copernicus GmbH

Publication Date: 2021

detail.hit.zdb_id: 2217985-9

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