Inventing the Ice Age: The Rôle of Louis Agassiz

2007 ◽  
pp. 41-54
Keyword(s):  
Ice Age ◽  
Louis Agassiz

scholarly journals Resonant Forcing of the Climate System in Subharmonic Modes

2020 ◽  
Vol 8 (1) ◽  
pp. 60 ◽  
Author(s):  
Jean-Louis Pinault
Keyword(s):  
Climate Variability ◽  
Atmospheric Carbon Dioxide ◽  
Rossby Waves ◽  
Thermohaline Circulation ◽  
Climate System ◽  
Ice Age ◽  
Polar Ice ◽  
Ice Caps ◽  
Resonant Forcing

During recent decades observation of climate archives has raised several questions. Concerning the mid-Pleistocene transition problem, conflicting sets of hypotheses highlight either the role of ice sheets or atmospheric carbon dioxide in causing the increase in duration and severity of ice age cycles. The role of the solar irradiance modulations in climate variability is frequently referenced but the underlying physical justifications remain most mysterious. Here, we extend the key mechanisms involving the oceanic Rossby waves in climate variability, to very long-period, multi-frequency Rossby waves winding around the subtropical gyres. Our study demonstrates that the climate system responds resonantly to solar and orbital forcing in eleven subharmonic modes. We advocate new hypotheses on the evolution of the past climate, implicating the deviation between forcing periods and natural periods according to the subharmonic modes, and the polar ice caps while challenging the role of the thermohaline circulation.

scholarly journals Simulated retreat of Jakobshavn Isbræ since the Little Ice Age controlled by geometry

2018 ◽  
Vol 12 (7) ◽  
pp. 2249-2266 ◽  
Author(s):  
Nadine Steiger ◽  
Kerim H. Nisancioglu ◽  
Henning Åkesson ◽  
Basile de Fleurian ◽  
Faezeh M. Nick
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Climate Forcing ◽  
Relative Role ◽  
Regional Warming ◽  
History Of ◽  
The Impact ◽  
Term Response

Abstract. Rapid retreat of Greenland's marine-terminating glaciers coincides with regional warming trends, which have broadly been used to explain these rapid changes. However, outlet glaciers within similar climate regimes experience widely contrasting retreat patterns, suggesting that the local fjord geometry could be an important additional factor. To assess the relative role of climate and fjord geometry, we use the retreat history of Jakobshavn Isbræ, West Greenland, since the Little Ice Age (LIA) maximum in 1850 as a baseline for the parameterization of a depth- and width-integrated ice flow model. The impact of fjord geometry is isolated by using a linearly increasing climate forcing since the LIA and testing a range of simplified geometries. We find that the total length of retreat is determined by external factors – such as hydrofracturing, submarine melt and buttressing by sea ice – whereas the retreat pattern is governed by the fjord geometry. Narrow and shallow areas provide pinning points and cause delayed but rapid retreat without additional climate warming, after decades of grounding line stability. We suggest that these geometric pinning points may be used to locate potential sites for moraine formation and to predict the long-term response of the glacier. As a consequence, to assess the impact of climate on the retreat history of a glacier, each system has to be analyzed with knowledge of its historic retreat and the local fjord geometry.

scholarly journals The Climate Response to Multiple Volcanic Eruptions Mediated by Ocean Heat Uptake: Damping Processes and Accumulation Potential

2018 ◽  
Vol 31 (21) ◽  
pp. 8669-8687 ◽  
Author(s):  
Mukund Gupta ◽  
John Marshall
Keyword(s):  
Time Scales ◽  
Volcanic Eruption ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Fast Time ◽  
Cold Surface ◽  
Ocean Heat Uptake ◽  
Accumulation Potential ◽  
Damping Rate

A hierarchy of models is used to explore the role of the ocean in mediating the response of the climate to a single volcanic eruption and to a series of eruptions by drawing cold temperature anomalies into its interior, as measured by the ocean heat exchange parameter q (W m−2 K−1). The response to a single (Pinatubo-like) eruption comprises two primary time scales: one fast (year) and one slow (decadal). Over the fast time scale, the ocean sequesters cooling anomalies induced by the eruption into its depth, enhancing the damping rate of sea surface temperature (SST) relative to that which would be expected if the atmosphere acted alone. This compromises the ability to constrain atmospheric feedback rates measured by λ (~1 W m−2 K−1) from study of the relaxation of SST back toward equilibrium, but yields information about the transient climate sensitivity proportional to λ + q. Our study suggests that q can significantly exceed λ in the immediate aftermath of an eruption. Shielded from damping to the atmosphere, the effect of the volcanic eruption persists on longer decadal time scales. We contrast the response to an “impulse” from that of a “step” in which the forcing is kept constant in time. Finally, we assess the “accumulation potential” of a succession of volcanic eruptions over time, a process that may in part explain the prolongation of cold surface temperatures experienced during, for example, the Little Ice Age.

The status of research on glaciers and global glacier recession: a review

2006 ◽  
Vol 30 (3) ◽  
pp. 285-306 ◽  
Author(s):  
Roger G. Barry
Keyword(s):  
Global Climate ◽  
Ice Age ◽  
Remotely Sensed Data ◽  
New Techniques ◽  
Mountain Glaciers ◽  
Glacier Recession ◽  
The Status ◽  
Global Sea Level ◽  
Key Indicators

Mountain glaciers are key indicators of climate change, although the climatic variables involved differ regionally and temporally. Nevertheless, there has been substantial glacier retreat since the Little Ice Age and this has accelerated over the last two to three decades. Documenting these changes is hampered by the paucity of observational data. This review outlines the measurements that are available, new techniques that incorporate remotely sensed data, and major findings around the world. The focus is on changes in glacier area, rather than estimates of mass balance and volume changes that address the role of glacier melt in global sea-level rise. The glacier observations needed for global climate monitoring are also outlined.

scholarly journals A importância da acção do frio do Quaternário final em Portugal e suas implicações nas morfodinâmicas de vertente.

2012 ◽  
Vol 5 (2) ◽  
pp. 421
Author(s):  
António Sousa Pedrosa
Keyword(s):  
Little Ice Age ◽  
Late Quaternary ◽  
Climatic Conditions ◽  
Ice Age ◽  
Glacial Deposits ◽  
Central Portugal

Resumo   De entre os  factores que tiveram maior influência na evolução do relevo de Portugal no decurso final do Quaternário é incontestável que o frio e os processos que lhe estão associados tiveram um papel muito importante na modelação das formas de relevo. Neste trabalho procuraremos fazer uma síntese dos principais aspectos da evolução das vertentes relacionados com os frio, inferir através dos vestígios que chegaram até ao nossos dias quais as condições morfo-climáticas em que ocorreram e quais os processos que lhes estavam encontravam associados. Realçamos assim o papel da acção dos glaciares nas áreas onde ocorreram assim como a importância dos processos periglaciares na evolução das vertentes. O período tardiglaciar também se mostrou marcante na dinâmica de vertentes tendo mobilizado e remobilizado muito material nas vertentes através de solifluxões generalizadas levando muitas delas à sua regularização. O período conhecido como a pequena idade do gelo também deixou as suas marcas na dinâmica das vertentes às quais se associam as escombreiras de gravidade. Por fim enfatizamos um pouco o papel do frio na actual morfodinâmica de vertentes no Norte de Centro de Portugal.   Palavras-chave: Norte de Portugal; Montanhas, depósitos glaciares, depósitos periglaciares, dinâmica de vertentes Summary   Among the factors that most influenced the evolution of the relief of Portugal during the late Quaternary is incontestable that the cold and the processes associated with it had a very important role in modeling the forms of relief. In this paper, we will try to summarize the importance that the cold had on the evolution of slopes, inferred through the vestiges that have come down to our day, which morpho-climatic conditions in which they occur, and also what processes if they were associated with. Thus enhancing the role of action in areas where glaciers have occurred and the importance of periglacial processes in the evolution of the slopes. In tardiglaciar the dynamics of slopes was very active and mobilized a lot of material through the process of solifluction regularized many of them. The period known as the Little Ice Age has also left its mark on the dynamic slopes which relate to tailings heaps of gravity. Finally we emphasize the role of cold in the current slopes of morphodynamics in north and central Portugal.   Keywords: North of Portugal; mountains, glacial deposits, periglacial deposits, morphodynamics of slopes 

scholarly journals Influence of temporally varying weatherability on CO<sub>2</sub>–climate coupling and ecosystem change in the late Paleozoic

2020 ◽  
Author(s):  
Jon D. Richey ◽  
Isabel P. Montañez ◽  
Yves Goddéris ◽  
Cindy V. Looy ◽  
Neil P. Griffis ◽  
...  
Keyword(s):  
Steady State ◽  
Ice Age ◽  
Secular Change ◽  
Ecosystem Change ◽  
Late Paleozoic ◽  
Relative Role ◽  
C Cycle ◽  
Ecosystem Perturbation ◽  
Atmospheric Pco2

Abstract. Earth's penultimate icehouse, the Late Paleozoic Ice Age (LPIA), was a time of dynamic glaciation and repeated ecosystem perturbation, under conditions of substantial variability in atmospheric pCO2 and O2. Improved constraints on the evolution of atmospheric pCO2 and O2 : CO2 during the LPIA and its subsequent demise to permanent greenhouse conditions is crucial for better understanding the nature of linkages between atmospheric composition, climate, and ecosystem perturbation during this time. We present a new and age-recalibrated pCO2 reconstruction for a 40-Myr interval (~313 to 273 Ma) of the late Paleozoic that (1) confirms a previously hypothesized strong CO2-glaciation linkage, (2) documents synchroneity between major pCO2 and O2 : CO2 changes and compositional turnovers in terrestrial and marine ecosystems, (3) lends support for a modeled progressive decrease in the CO2 threshold for initiation of continental ice sheets during the LPIA, and (4) indicates a likely role of CO2 and O2 : CO2 thresholds in floral ecologic turnovers. Modeling of the relative role of CO2 sinks and sources, active during the LPIA and its demise, on steady-state pCO2 using an intermediate complexity climate-C cycle model (GEOCLIM) and comparison to the new multi-proxy CO2 record provides new insight into the relative influences of the uplift of the Central Pangaean Mountains, intensifying aridification, and increasing mafic rock to-granite rock ratio of outcropping rocks on the global efficiency of CO2 consumption and secular change in steady-state pCO2 through the late Paleozoic.

Evolution of the Ofanto River delta from the ‘Little Ice Age’ to modern times: Implications of large-scale synoptic patterns

The Holocene ◽  
2018 ◽  
Vol 28 (12) ◽  
pp. 1948-1967 ◽  
Author(s):  
Vincenzo De Santis ◽  
Massimo Caldara ◽  
Antonella Marsico ◽  
Domenico Capolongo ◽  
Luigi Pennetta
Keyword(s):  
Large Scale ◽  
Low Pressure ◽  
River Delta ◽  
Ice Age ◽  
Aerial Photographs ◽  
Anthropogenic Factors ◽  
Synoptic Patterns ◽  
Delta Evolution ◽  
Circulation Mode

We reconstruct the evolution of the Ofanto River delta from the 17th century to the present using historical maps (1600–1850), official IGM topographic maps (1850–1980) and recent aerial photographs (2015), and we compare long-term morphological changes with the evolution of the delta of the Volturno River during the same time period. The aim of this study is to define the role of climatic (flood frequency, synoptic pressure patterns) and anthropogenic factors (deforestation, anthropogenic sediment subtraction of river sediment) in the evolution of the Ofanto delta. We analysed the importance of each factor on the evolution of the delta and compared them with the simultaneous behaviour of the Volturno delta to highlight the role of large-scale synoptic pressure patterns. We found that the main driver of different delta evolution phases is weather-climatic condition, while anthropogenic factors interacted with the delta evolution in different ways but did not control the first-order evolution. In particular, analysing the data on recent floods, we found that the most favourable situations for both rivers are omega-blocking, deep low-pressure trough and strong meridional circulation (mode Ω) which create Mediterranean low-pressure systems. Instead, a zonal circulation (mode W) can only cause floods on Volturno. Because the evolution of a delta is driven by the frequency of floods, and because we found that the frequency of floods is guided by synoptic patterns, a relationship can be established between delta evolution and synoptic patterns in the past. Consequently, past phases of the contemporary progradation of the Ofanto and Volturno deltas suggest the increasing frequency of mode Ω, while phases of simultaneous progradation of the Volturno delta and stability and/or retreat of the Ofanto delta are indicative of the increasing frequency of mode W. The only exception occurred during the last evolutionary phase (60 years), when anthropogenic sediment subtraction was prevalent.

Climate change and rapid ice melt: Suggestions from abrupt permafrost degradation and ice melting in an alpine ice cave

2019 ◽  
Vol 43 (4) ◽  
pp. 561-573 ◽  
Author(s):  
Renato R. Colucci ◽  
Mauro Guglielmin
Keyword(s):  
Cooling Effect ◽  
Ice Age ◽  
European Alps ◽  
Permafrost Degradation ◽  
Positive Feedbacks ◽  
Ice Melt ◽  
Cave System ◽  
Rock Temperature ◽  
Air Circulation

Among the different elements of the mountain cryosphere, ice caves still represent the lesser known part of it. Here we present a seven-year-long record of air and rock temperature in a cave of the southeastern European Alps. We demonstrate how the presence of a permanent ice deposit in the cave is not only related to the net cooling effect of the air circulation, as it is well known, but also to the occurrence of relict permafrost. Through a detailed representation of temperature patterns inside the cave, both air and rock data show how after a period of perennially subzero (cryotic) conditions in the rock, ongoing anthropogenic climate warming is responsible for permafrost degradation despite the cooling effect of the air circulation in the cave. Data support the important role of cryotic conditions in the rock in preserving a permanent ice cave deposit in the present climate, even once the possible relict permafrost inherited from the past disappears. A thickness of 29–44 m of permafrost, possibly formed during the Little Ice Age, has now almost completely disappeared. The present abrupt ice degradation observed in this cave is further exacerbated by positive feedbacks related to warmer air circulation in the cave system.

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