scholarly journals Temporal and spatial structure of multi-millennial temperature changes at high latitudes during the Last Interglacial

2014 ◽  
Vol 103 ◽  
pp. 116-133 ◽  
Author(s):  
Emilie Capron ◽  
Aline Govin ◽  
Emma J. Stone ◽  
Valérie Masson-Delmotte ◽  
Stefan Mulitza ◽  
...  
Keyword(s):  
Spatial Structure ◽  
High Latitudes ◽  
Last Interglacial ◽  
Temperature Changes ◽  
Temporal And Spatial

PMIP4/CMIP6 last interglacial simulations using three different versions of MIROC: importance of vegetation

2021 ◽  
Author(s):  
Ryouta O'ishi ◽  
Wing-Le Chan ◽  
Ayako Abe-Ouchi ◽  
Sam Sherriff-Tadano ◽  
Rumi Ohgaito ◽  
...  
Keyword(s):  
Feedback Mechanism ◽  
Climate Feedback ◽  
High Latitudes ◽  
Last Interglacial ◽  
Proxy Data ◽  
Area Index ◽  
Vegetation Feedback ◽  
Temperature Changes ◽  
Northern High Latitude ◽  
Series Of Experiments

<p>We carry out three sets of last interglacial (LIG) experiments, named lig127k, and of pre-industrial experiments, named piControl, both as part of PMIP4/CMIP6 using three versions of the MIROC model: MIROC4m, MIROC4m-LPJ, and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high-latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Globally averaged temperature changes are −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L).<br>Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows annual mean warming signals at northern high latitudes, as indicated by proxy data. In contrast, the latest Earth system model (ESM) of MIROC, MIROC-ES2L, which considers only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the Northern Hemisphere. Results from the series of experiments show that the inclusion of full vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.</p>

scholarly journals PMIP4/CMIP6 last interglacial simulations using three different versions of MIROC: importance of vegetation

2021 ◽  
Vol 17 (1) ◽  
pp. 21-36
Author(s):  
Ryouta O'ishi ◽  
Wing-Le Chan ◽  
Ayako Abe-Ouchi ◽  
Sam Sherriff-Tadano ◽  
Rumi Ohgaito ◽  
...  
Keyword(s):  
Feedback Mechanism ◽  
Climate Feedback ◽  
High Latitudes ◽  
Last Interglacial ◽  
Proxy Data ◽  
Area Index ◽  
Vegetation Feedback ◽  
Temperature Changes ◽  
Northern High Latitude ◽  
Series Of Experiments

Abstract. We carry out three sets of last interglacial (LIG) experiments, named lig127k, and of pre-industrial experiments, named piControl, both as part of PMIP4/CMIP6 using three versions of the MIROC model: MIROC4m, MIROC4m-LPJ, and MIROC-ES2L. The results are compared with reconstructions from climate proxy data. All models show summer warming over northern high-latitude land, reflecting the differences between the distributions of the LIG and present-day solar irradiance. Globally averaged temperature changes are −0.94 K (MIROC4m), −0.39 K (MIROC4m-LPJ), and −0.43 K (MIROC-ES2L). Only MIROC4m-LPJ, which includes dynamical vegetation feedback from the change in vegetation distribution, shows annual mean warming signals at northern high latitudes, as indicated by proxy data. In contrast, the latest Earth system model (ESM) of MIROC, MIROC-ES2L, which considers only a partial vegetation effect through the leaf area index, shows no change or even annual cooling over large parts of the Northern Hemisphere. Results from the series of experiments show that the inclusion of full vegetation feedback is necessary for the reproduction of the strong annual warming over land at northern high latitudes. The LIG experimental results show that the warming predicted by models is still underestimated, even with dynamical vegetation, compared to reconstructions from proxy data, suggesting that further investigation and improvement to the climate feedback mechanism are needed.

Impact of a strong temperature gradient on grain growth in films

2021 ◽  
Author(s):  
Dana Zöllner
Keyword(s):  
Temperature Gradient ◽  
Grain Growth ◽  
Annealing Temperature ◽  
Three Dimensional ◽  
Drag Effect ◽  
Temperature Changes ◽  
Grain Boundary Mobility ◽  
Microstructural Coarsening ◽  
Temporal And Spatial ◽  
Model Algorithm

Abstract The migration of grain boundaries and, therewith, the phenomenon of grain growth depend strongly on the annealing temperature. Generally, higher temperatures are associated with higher mobilities of the boundaries and therewith faster microstructural coarsening. In the present study, the influence of a strong temperature gradient on grain growth in thin films is investigated. To that aim, a modified three-dimensional Potts model algorithm is employed, where the annealing temperature changes with the thickness of the sample taking grain boundary mobility and energy into account. The resulting drag effect has serious consequences for the temporal and spatial evolution of the grain microstructure.

The Atlantic Meridional Overturning Circulation (AMOC) simulated during interglacials and its impact on climate

2021 ◽  
Author(s):  
Zhiyi Jiang ◽  
Chris Brierley ◽  
David Thornalley ◽  
Sophie Sax
Keyword(s):  
Spatial Structure ◽  
Surface Temperature ◽  
Global Climate ◽  
Atlantic Meridional Overturning Circulation ◽  
Meridional Overturning Circulation ◽  
Last Interglacial ◽  
Overturning Circulation ◽  
Poleward Heat Transport ◽  
Meridional Overturning ◽  
Proxy Reconstructions

<p>The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of poleward heat transport and an important part of the global climate system. How it responded to past changes inforcing, such as experienced during Quaternary interglacials, is an intriguing and open question. Previous modelling studies suggest an enhanced AMOC in the mid-Holocene compared to the pre-industrial period. In previous simulations from the Palaeoclimate Modelling Intercomparison Project (PMIP), this arose from feedbacks between sea ice and AMOC changes, which also depended on resolution. Here I present aninitial analysis of the recently available PMIP4 simulations. This shows the overall strength of the AMOC does not markedly change between the mid-Holocene and piControl experiments (at least looking at the maximum of the mean meridional mass overturning streamfunction below 500m at 30<sup>o</sup>N and 50<sup>o</sup>N). This is not inconsistent with the proxy reconstructions using sortable silt and Pa/Th for the mid-Holocene. Here we analyse changes in the spatial structure of the meridional overturning circulation, along with their fingerprints on the surface temperature (computed through regression). We then estimate the percentage of the simulated surface temperature changes between the mid-Holocene and pre-industrial period that can be explained by AMOC. Furthermore, the analysis for the changes in the AMOC spatial structure has been extended to see if the same patterns of change hold for the last interglacial. The simulations will be compared to existing proxy reconstructions, as well as new palaeoceanographic reconstructions.</p>

scholarly journals The pliocene record of climatic change: equator-to-pole biotic response

1992 ◽  
Vol 6 ◽  
pp. 78-78
Author(s):  
Thomas M. Cronin ◽  
H.J. Dowsett
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
North Pacific ◽  
Global Climate ◽  
North Pacific Ocean ◽  
Thermal Gradients ◽  
High Latitudes ◽  
Near Surface ◽  
Temperature Changes ◽  
The North

Pliocene faunal events in tropical and subtropical regions of the Americas and the Caribbean have been causally linked to global climatic events, particularly, progressive cooling and increased amplitude of climatic cycles between 3.5 and 2.0 Ma. However, the rate and magnitude of Pliocene temperature changes has been determined in only a few climate proxy records. Our study contrasts paleoceanographic conditions at 3 Ma, an extremely warm period in many areas, with conditions 2.4 Ma, a much cooler interval, in equator-to-pole transects for the North Atlantic and the North Pacific Oceans. By using microfaunal data (ostracodes from ocean margin environments and planktic foraminifers from deep sea cores), quantitative factor analytic and modern analog dissimilarity coefficient analyses were carried out on faunas from the following sections.Our studies lead to the following conclusions: (1) Equator-to-pole thermal gradients in the oceans at 3.0 Ma were not as steep as they are today, but thermal gradients at 2.4 Ma were steeper than those today; (2)At 3 Ma middle to high latitudes were substantially warmer than today, but tropical regions were about the same; (3)Substantial cooling occurred in middle and high latitudes in the western North Pacific Ocean and the western North Atlantic between 3 Ma and 2.4 Ma; (4)Ocean water temperatures off the southeastern U.S. remained the same or cooled only slightly between 3 Ma and 2.4 Ma. Our results support the hypothesis that ocean circulation changes, probably resulting from the closure of near surface water by the Isthmus of Panama, had significant impact on equator-to-pole heat transport and global climate between about 3 and 2.4 Ma. They also argue against the hypothesis that climatically induced ocean temperature changes were directly linked to a major marine extinction in the southwestern North Atlantic and Caribbean.

scholarly journals Climatology of the mesopause density using a global distribution of meteor radars

2018 ◽  
Author(s):  
Wen Yi ◽  
Xianghui Xue ◽  
Iain M. Reid ◽  
Damian J. Murphy ◽  
Chris M. Hall ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
High Latitudes ◽  
Meteor Radar ◽  
Low Latitude ◽  
Wave Forcing ◽  
Spring Equinox ◽  
Spatial Coverage ◽  
Low Latitudes ◽  
Variation Characteristics ◽  
Temporal And Spatial

Abstract. The existing distribution of meteor radars located from high- to low-latitude regions provides a favourable temporal and spatial coverage for investigating the climatology of the global mesopause density. In this study, we report the climatology of the mesopause density estimated using multiyear observations from nine meteor radars, namely, the Davis Station (68.6° S, 77.9° E), Svalbard (78.3° N, 16° E) and Tromsø (69.6° N, 19.2° E) meteor radars located at high latitudes, the Mohe (53.5° N, 122.3° E), Beijing (40.3° N, 116.2° E), Mengcheng (33.4° N, 116.6° E) and Wuhan (30.5° N, 114.6° E) meteor radars located in the mid-latitudes, and the Kunming (25.6° N, 103.8° E) and Darwin (12.3° S, 130.8° E) meteor radars located at low latitudes. The daily mean density was estimated using ambipolar diffusion coefficients derived from the meteor radars and temperatures from the Microwave Limb Sounder (MLS) on board the Aura satellite. The seasonal variations in the Davis Station meteor radar densities in the southern polar mesopause are mainly dominated by an annual oscillation (AO). The mesopause densities observed by the Svalbard and Tromsø meteor radars at high latitudes and the Mohe and Beijing meteor radars at high mid-latitudes in the Northern Hemisphere show mainly an AO and a relatively weak semiannual oscillation (SAO). The mesopause densities observed by the Mengcheng and Wuhan meteor radars at lower mid-latitudes and the Kunming and Darwin meteor radars at low latitudes show mainly an AO. The SAO is evident in the Northern Hemisphere, especially at high latitudes, and its largest amplitude, which is detected at the Tromsø meteor radar, is comparable to the AO amplitudes. These observations indicate that the mesopause densities over the southern and northern high latitudes exhibit a clear seasonal asymmetry. The maxima of the yearly variations in the mesopause densities display a clear temporal variation across the spring equinox as the latitude decreases; these latitudinal variation characteristics may be related to latitudinal changes influenced by gravity wave forcing. In addition to an AO, the mesopause densities over low latitudes also clearly show a variation with a periodicity of 30–60 days related to the Madden-Julian oscillation in the subtropical troposphere.

Ocean climate response to anomalous surface buoyancy and momentum fluxes

2020 ◽  
Author(s):  
Rene Navarro-Labastida ◽  
Riccardo Farneti
Keyword(s):  
Heat Flux ◽  
North Atlantic ◽  
Surface Heat ◽  
High Latitudes ◽  
Temperature Changes ◽  
Ocean Climate ◽  
The North ◽  
Anomalous Surface ◽  
Low Latitudes ◽  
The North Atlantic

<p>The aim of the project is to evaluate the response of the global ocean climate to anomalous surface fluxes in terms of ocean heat uptake and circulation changes. All simulations have been performed with the NOAA-GFDL Modular Ocean Model (MOM) version 5. Ocean-only MOM has been integrated toward a near-equilibrium state using as multicentinal initial conditions derivated from a former CORE-I protocol implementation (Griffies et al., 2009). After equilibrium, a restored control simulation has been obtained by a further 70 years of integration while effective total air-sea heat fluxes and freshwater fluxes were stored at daily intervals. A second control simulation has been obtained by the prescription of these storage fluxes. Differences between the restored and prescribed fluxes controls are rather small. Explicit flux sensitivity experiments are proposed by the Flux-Anomaly-Forced Model Intercomparison Project (FAFMIP) in which prescribed surface flux perturbations are applied to the ocean in separated simulations (Gregory et al., 2016). Experiments are 70 years long and branch from piControl conditions. Both wind stress and freshwater anomalies implies nearly-to-zero temperature changes in volume mean temperature. Only the last implies a rather small cooling effect after year 50 of integration. In contrast, anomalous heat flux causes significant volume mean temperature changes. Observed total temperature changes are solely determined by the local addition of heat implying vanishing of the redistribution effect in the entire ocean by inter-basin exchanges and vertical mixing. So far, surface heat anomalies produce the most notable zonal-mean change in ocean temperature. Strong positive temperature change is observed along the top ocean while deepening of temperature anomalies occurs at high latitudes in both hemispheres. Both added and redistributed temperature tracers show maxima in the same area. In most cases, both processes are proportionally inverse. Except for the northern ocean, added temperature tracer is roughly limited to the first 1000 m deep. In contrast, redistributed temperature tracer shows the cooling of subtropical areas and the warming of both the tropical and southern ocean. Maximum at the North Atlantic is possibly due to atmosphere-sea feedbacks, while near-surface tropical and subtropical changes are due to redistribution processes. Heat is mainly taken as a passive tracer in the North Atlantic Ocean and along the entire Southern Ocean. Warming up of mid and low latitudes by redistribution processes is due to the weakening of the Atlantic Meridional Overturning Circulation (AMOC). In turn, changes in AMOC are dominated by surface heat flux changes. The reduction of northward heat transport cools down high latitudes near the surface causing low latitudes to warm up.</p><p> </p>

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