On the Structure and Origin of Major Glaciation Cycles 1. Linear Responses to Milankovitch Forcing

1992 ◽  
Vol 7 (6) ◽  
pp. 701-738 ◽  
Author(s):  
J. Imbrie ◽  
E. A. Boyle ◽  
S. C. Clemens ◽  
A. Duffy ◽  
W. R. Howard ◽  
...  
Keyword(s):  
Milankovitch Forcing

scholarly journals Can we predict the duration of an interglacial?

2012 ◽  
Vol 8 (2) ◽  
pp. 1057-1088 ◽  
Author(s):  
P. C. Tzedakis ◽  
E. W. Wolff ◽  
L. C. Skinner ◽  
V. Brovkin ◽  
D. A. Hodell ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Sea Level ◽  
Predictive Power ◽  
The Other ◽  
Systematic Evaluation ◽  
Middle Pleistocene ◽  
Boreal Summer ◽  
History Of ◽  
Background Climate ◽  
Milankovitch Forcing

Abstract. Differences in the duration of interglacials have long been apparent in palaeoclimate records of the Late and Middle Pleistocene. However, a systematic evaluation of such differences has been hampered by the lack of a metric that can be applied consistently through time and by difficulties in separating the local from the global component in various proxies. This, in turn, means that a theoretical framework with predictive power for interglacial duration has remained elusive. Here we propose that the interval between the terminal oscillation of the bipolar-seesaw and three thousand years (kyr) before its first major reactivation provides an estimate that approximates the length of the sea-level highstand, a measure of interglacial duration. We apply this concept to interglacials of the last 800 kyr by using a recently-constructed record of interhemispheric variability. The onset of interglacials occurs within 2 kyr of the peak in boreal summer insolation and is consistent with the canonical view of Milankovitch forcing dictating the broad timing of interglacials. Glacial inception always takes place when obliquity is decreasing and never after the obliquity minimum. The phasing of precession and obliquity appears to influence the persistence of interglacial conditions over one or two insolation peaks, leading to shorter (~13 kyr) and longer (~28 kyr) interglacials. Glacial inception occurs approximately 10 kyr after peak interglacial conditions in temperature and CO2, representing an interglacial "relaxation" time over which gradual cooling takes place. Second-order differences in duration may be a function of stochasticity in the climate system, or small variations in background climate state and the magnitude of feedbacks and mechanisms contributing to glacial iinception, and as such, difficult to predict. On the other hand, the broad duration of an interglacial may be determined by the phasing of astronomical parameters and the history of insolation, rather than the instantaneous forcing strength at inception.

scholarly journals Milankovitch Forcing and Meridional Moisture Flux in the Atmosphere: Insight from a Zonally Averaged Ocean–Atmosphere Model

2010 ◽  
Vol 23 (18) ◽  
pp. 4841-4855 ◽  
Author(s):  
Andrés Antico ◽  
Olivier Marchal ◽  
Lawrence A. Mysak ◽  
Françoise Vimeux
Keyword(s):  
Ocean Circulation ◽  
Hydrological Cycle ◽  
Circulation Model ◽  
Ice Cores ◽  
Moisture Flux ◽  
Meridional Overturning Circulation ◽  
Balance Model ◽  
Ocean Atmosphere ◽  
Atmosphere Model ◽  
Milankovitch Forcing

Abstract A 1-Myr-long time-dependent solution of a zonally averaged ocean–atmosphere model subject to Milankovitch forcing is examined to gain insight into long-term changes in the planetary-scale meridional moisture flux in the atmosphere. The model components are a one-dimensional (latitudinal) atmospheric energy balance model with an active hydrological cycle and an ocean circulation model representing four basins (Atlantic, Indian, Pacific, and Southern Oceans). This study finds that the inclusion of an active hydrological cycle does not significantly modify the responses of annual-mean air and ocean temperatures to Milankovitch forcing found in previous integrations with a fixed hydrological cycle. Likewise, the meridional overturning circulation of the North Atlantic Ocean is not significantly affected by hydrological changes. Rather, it mainly responds to precessionally driven variations of ocean temperature in subsurface layers (between 70- and 500-m depth) of this basin. On the other hand, annual and zonal means of evaporation rate and meridional flux of moisture in the atmosphere respond notably to obliquity-driven changes in the meridional gradient of annual-mean insolation. Thus, when obliquity is decreased (increased), the meridional moisture flux in the atmosphere is intensified (weakened). This hydrological response is consistent with deuterium excess records from polar ice cores, which are characterized by dominant obliquity cycles.

Milankovitch Forcing of the Last Interglacial Sea Level

Science ◽  
1994 ◽  
Vol 265 (5178) ◽  
pp. 1566-1568 ◽  
Author(s):  
T. J. Crowley ◽  
K.-Y. Kim
Keyword(s):  
Sea Level ◽  
Last Interglacial ◽  
Milankovitch Forcing

scholarly journals Can we predict the duration of an interglacial?

2012 ◽  
Vol 8 (5) ◽  
pp. 1473-1485 ◽  
Author(s):  
P. C. Tzedakis ◽  
E. W. Wolff ◽  
L. C. Skinner ◽  
V. Brovkin ◽  
D. A. Hodell ◽  
...  
Keyword(s):  
Sea Level ◽  
Predictive Power ◽  
The Other ◽  
Systematic Evaluation ◽  
Middle Pleistocene ◽  
Boreal Summer ◽  
History Of ◽  
Insolation Maximum ◽  
Background Climate ◽  
Milankovitch Forcing

Abstract. Differences in the duration of interglacials have long been apparent in palaeoclimate records of the Late and Middle Pleistocene. However, a systematic evaluation of such differences has been hampered by the lack of a metric that can be applied consistently through time and by difficulties in separating the local from the global component in various proxies. This, in turn, means that a theoretical framework with predictive power for interglacial duration has remained elusive. Here we propose that the interval between the terminal oscillation of the bipolar seesaw and three thousand years (kyr) before its first major reactivation provides an estimate that approximates the length of the sea-level highstand, a measure of interglacial duration. We apply this concept to interglacials of the last 800 kyr by using a recently-constructed record of interhemispheric variability. The onset of interglacials occurs within 2 kyr of the boreal summer insolation maximum/precession minimum and is consistent with the canonical view of Milankovitch forcing pacing the broad timing of interglacials. Glacial inception always takes place when obliquity is decreasing and never after the obliquity minimum. The phasing of precession and obliquity appears to influence the persistence of interglacial conditions over one or two insolation peaks, leading to shorter (~ 13 kyr) and longer (~ 28 kyr) interglacials. Glacial inception occurs approximately 10 kyr after peak interglacial conditions in temperature and CO2, representing a characteristic timescale of interglacial decline. Second-order differences in duration may be a function of stochasticity in the climate system, or small variations in background climate state and the magnitude of feedbacks and mechanisms contributing to glacial inception, and as such, difficult to predict. On the other hand, the broad duration of an interglacial may be determined by the phasing of astronomical parameters and the history of insolation, rather than the instantaneous forcing strength at inception.

scholarly journals Milankovitch forcing of Early Jurassic wildfires

2019 ◽  
Author(s):  
Teuntje Parnassia Hollaar ◽  
Sarah Jane Baker ◽  
Jean-Francois Deconinck ◽  
Luke Mander ◽  
Micha Ruhl ◽  
...  
Keyword(s):  
High Resolution ◽  
Elemental Concentration ◽  
Clay Mineralogy ◽  
Early Jurassic ◽  
Orbital Forcing ◽  
Quaternary Deposits ◽  
Environmental Perturbations ◽  
Earth’S Climate ◽  
In Fire ◽  
Milankovitch Forcing

The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming and the frequency of large wildfires appears to be increasing. Recent research has indicated that Quaternary deposits reveal that wildfires respond to orbital forcings; however, to date no study has been able to test whether wildfire activity corresponds to changes over Milankovitch timescales in the deep past. A high-resolution astrochronology exists for the Upper Pliensbachian in the Llanbedr (Mochras Farm) borehole (NW Wales). Ruhl et al. (2016) show that elemental concentration recorded by hand-held X-ray fluorescence (XRF), changes mainly at periodicities of ~21,000 year, ~100,000 year and ~400,000 year, and which can be related to visually described sedimentary bundles. We have quantified the abundance of fossil charcoal at a high resolution (10-15 cm) to test the hypothesis that these well-preserved climatic cycles influenced fire activity throughout this globally warm period. Preliminary results suggest that variations in charcoal abundance are coupled to Milankovitch forcings over periods of ~21,000 and ~100,000 years. We suggest that these changes in fire relate to changes in seasonality and monsoonal activity that drove changes in vegetation that are linked to variations in the orbital forcing. Supplementary to the charcoal record, a high-resolution clay mineralogy dataset has been generated to further explain the climatic cyclicity observed in the wildfire record regarding the hydrology on land.

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