Hydromechanical Rock Slope Damage During Late Pleistocene and Holocene Glacial Cycles in an Alpine Valley

<p>During the Pleistocene (approximately 2.6 Ma to present) glacial to interglacial climate variability evolved from dominantly 40 kyr cyclicity (Early Pleistocene) to 100 kyr cyclicity (Late Pleistocene to present). Three aspects of this period remain poorly understood: Why did the dominant frequency of climate oscillation change, given that no major changes in orbital forcing occurred? Why are the longer glacial cycles of the Late Pleistocene characterised by a more asymmetric form with abrupt terminations? And how can the Late Pleistocene climate be controlled by 100 kyr cyclicity when astronomical forcings of this frequency are so much weaker than those operating on shorter periods? Here we show that the decreasing frequency and increasing asymmetry that characterise Late Pleistocene ice age cycles both emerge naturally in dynamical systems in response to increasing system complexity, with collapse events (terminations) occuring only once a critical state has been reached. Using insights from network theory we propose that evolution to a state of criticality involves progressive coupling between climate system 'nodes', which ultimately allows any component of the climate system to trigger a globally synchronous termination. We propose that the climate state is synchronised at the 100 kyr frequency, rather than at shorter periods, because eccentricity-driven insolation variability controls mean temperature change globally, whereas shorter-period astronomical forcings only affect the spatial pattern of thermal forcing and thus do not favour global synchronisation. This dynamical systems framework extends and complements existing theories by accomodating the differing mechanistic interpretations of previous studies without conflict.</p>

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Symmetry of Late Pleistocene glacial cycles in records of the Antarctic Vostok and Dome C stations

Doklady Earth Sciences ◽

10.1134/s1028334x06020395 ◽

2006 ◽

Vol 407 (1) ◽

pp. 326-329 ◽

Cited By ~ 4

Author(s):

N. V. Vakulenko ◽

V. M. Kotlyakov ◽

A. S. Monin ◽

D. M. Sonechkin

Keyword(s):

Late Pleistocene ◽

Glacial Cycles ◽

The Antarctic

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RECONSTRUCTING LATE PLEISTOCENE NORTH PACIFIC ICE-RAFTING HISTORY THROUGH TWO GLACIAL CYCLES

10.1130/abs/2020se-344940 ◽

2020 ◽

Author(s):

Casey L. Maslock ◽

◽

Katherine T. Rice ◽

Zachary Strasberg ◽

Colleen M. Ranieri ◽

...

Keyword(s):

Late Pleistocene ◽

North Pacific ◽

Glacial Cycles ◽

Ice Rafting

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Southern Ocean upwelling, Earth’s obliquity, and glacial-interglacial atmospheric CO2 change

Science ◽

10.1126/science.abd2115 ◽

2020 ◽

Vol 370 (6522) ◽

pp. 1348-1352

Author(s):

Xuyuan E. Ai ◽

Anja S. Studer ◽

Daniel M. Sigman ◽

Alfredo Martínez-García ◽

François Fripiat ◽

...

Keyword(s):

Carbon Dioxide ◽

Late Pleistocene ◽

Atmospheric Carbon Dioxide ◽

Global Climate ◽

Nitrogen Isotope ◽

Ice Ages ◽

Glacial Cycles ◽

Atmospheric Carbon ◽

Carbon Dioxide Levels ◽

The Antarctic

Previous studies have suggested that during the late Pleistocene ice ages, surface-deep exchange was somehow weakened in the Southern Ocean’s Antarctic Zone, which reduced the leakage of deeply sequestered carbon dioxide and thus contributed to the lower atmospheric carbon dioxide levels of the ice ages. Here, high-resolution diatom-bound nitrogen isotope measurements from the Indian sector of the Antarctic Zone reveal three modes of change in Southern Westerly Wind–driven upwelling, each affecting atmospheric carbon dioxide. Two modes, related to global climate and the bipolar seesaw, have been proposed previously. The third mode—which arises from the meridional temperature gradient as affected by Earth’s obliquity (axial tilt)—can explain the lag of atmospheric carbon dioxide behind climate during glacial inception and deglaciation. This obliquity-induced lag, in turn, makes carbon dioxide a delayed climate amplifier in the late Pleistocene glacial cycles.

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Synchronism of Late Pleistocene glacial cycles with insolation variations on the equator

Doklady Earth Sciences ◽

10.1134/s1028334x07020365 ◽

2007 ◽

Vol 413 (1) ◽

pp. 292-296

Author(s):

N. V. Vakulenko ◽

V. M. Kotlyakov ◽

A. S. Monin ◽

D. M. Sonechkin

Keyword(s):

Late Pleistocene ◽

Glacial Cycles

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Millennial scale feedbacks determine the shape and rapidity of glacial termination

Nature Communications ◽

10.1038/s41467-021-22388-6 ◽

2021 ◽

Vol 12 (1) ◽

Cited By ~ 1

Author(s):

Stephen Barker ◽

Gregor Knorr

Keyword(s):

Sea Level ◽

Late Pleistocene ◽

Large Amplitude ◽

Climate Simulation ◽

Glacial Cycles ◽

Major Transitions ◽

Atmosphere System ◽

Ocean Atmosphere ◽

Recent Developments ◽

Abrupt Shifts

AbstractWithin the Late Pleistocene, terminations describe the major transitions marking the end of glacial cycles. While it is established that abrupt shifts in the ocean/atmosphere system are a ubiquitous component of deglaciation, significant uncertainties remain concerning their specific role and the likelihood that terminations may be interrupted by large-amplitude abrupt oscillations. In this perspective we address these uncertainties in the light of recent developments in the understanding of glacial terminations as the ultimate interaction between millennial and orbital timescale variability. Innovations in numerical climate simulation and new geologic records allow us to highlight new avenues of research and identify key remaining uncertainties such as sea-level variability.

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Roles of insolation forcing and CO2 forcing on Late Pleistocene seasonal sea surface temperatures

Nature Communications ◽

10.1038/s41467-021-26051-y ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kyung Eun Lee ◽

Steven C. Clemens ◽

Yoshimi Kubota ◽

Axel Timmermann ◽

Ann Holbourn ◽

...

Keyword(s):

Late Pleistocene ◽

Sea Surface ◽

Climate Forcing ◽

Sea Surface Temperatures ◽

Glacial Cycles ◽

Globigerinoides Ruber ◽

Surface Temperatures ◽

Winter Temperatures ◽

Paleoclimate Proxy ◽

Phase Differences

AbstractLate Pleistocene changes in insolation, greenhouse gas concentrations, and ice sheets have different spatially and seasonally modulated climatic fingerprints. By exploring the seasonality of paleoclimate proxy data, we gain deeper insight into the drivers of climate changes. Here, we investigate changes in alkenone-based annual mean and Globigerinoides ruber Mg/Ca-based summer sea surface temperatures in the East China Sea and their linkages to climate forcing over the past 400,000 years. During interglacial-glacial cycles, there are phase differences between annual mean and seasonal (summer and winter) temperatures, which relate to seasonal insolation changes. These phase differences are most evident during interglacials. During glacial terminations, temperature changes were strongly affected by CO2. Early temperature minima, ~20,000 years before glacial terminations, except the last glacial period, coincide with the largest temperature differences between summer and winter, and with the timing of the lowest atmospheric CO2 concentration. These findings imply the need to consider proxy seasonality and seasonal climate variability to estimate climate sensitivity.

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