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.

On the Mechanism of Pacific Multidecadal Climate Variability in CCSM3: The Role of the Subpolar North Pacific Ocean

2009 ◽  
Vol 39 (9) ◽  
pp. 2052-2076 ◽  
Author(s):  
Yafang Zhong ◽  
Zhengyu Liu
Keyword(s):  
Pacific Ocean ◽  
Negative Feedback ◽  
Positive Feedback ◽  
North Pacific ◽  
Rossby Waves ◽  
North Pacific Ocean ◽  
Climate System ◽  
Multidecadal Variability ◽  
Salinity Variability

Abstract Previous analyses of the Community Climate System Model, version 3 (CCSM3) standard integration have revealed pronounced multidecadal variability in the Pacific climate system. The purpose of the present work is to investigate physical mechanism underlying this Pacific multidecadal variability (PMV). To better isolate the mechanism that selects the long multidecadal time scale for the PMV, a few specifically designed sensitivity experiments are carried out. When the propagating Rossby waves are blocked in the subtropics from the midbasin, the PMV remains outstanding. In contrast, when the Rossby waves are blocked beyond the subtropics across the entire North Pacific, the PMV is virtually suppressed. It suggests that the PMV relies on propagating Rossby waves in the subpolar Pacific, whereas those in the subtropics are not critical. A novel mechanism of PMV is advanced based on a more comprehensive analysis, which is characterized by a crucial role of the subpolar North Pacific Ocean. The multidecadal ocean temperature and salinity anomalies may originate from the subsurface of the subpolar North Pacific because of the wave adjustment to the preceding basin-scale wind curl forcing. The anomalies then ascend to the surface and are amplified through local temperature–salinity convective feedback. Along the southward Oyashio, these anomalies travel to the Kuroshio Extension (KOE) region and are further intensified through a similar convective feedback. The oceanic temperature anomaly in the KOE is able to feed back to the large-scale atmospheric circulation, inducing a wind curl anomaly over the subpolar North Pacific, which in turn generates anomalous oceanic circulation and causes temperature and salinity variability in the subpolar subsurface. Thereby, a closed loop of PMV is established in the form of an extratropical delayed oscillator. The phase transition of PMV is driven by the delayed negative feedback that resides in the wave adjustment of the subpolar North Pacific via propagating Rossby waves, whereas the convective positive feedback provides the growth mechanism. A significant role of salinity variability is unveiled in both the delayed negative feedback and convective positive feedback.

scholarly journals On the Milankovitch sensitivity of the Quaternary deep-sea record

2013 ◽  
Vol 9 (2) ◽  
pp. 1237-1257
Author(s):  
W. H. Berger
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Climate Variability ◽  
Deep Sea ◽  
Climate System ◽  
Ice Age ◽  
External Forcing ◽  
Orbital Forcing ◽  
Early Pliocene ◽  
System A

Abstract. The response of the climate system to external forcing has become an item of prime interest in the context of global warming, especially with respect to the rate of melting land-based ice masses. The deep-sea record of ice-age climate change has been useful in assessing the sensitivity of the climate system to such forcing, notably to orbital forcing, which is well-known for the last several million years. When comparing response and forcing, one finds that sensitivity varies greatly through time, apparently in dependence on the state of the system. The changing stability of ice masses presumably is the underlying cause for the changing state of the system. A buildup of vulnerable ice masses within the latest Tertiary, when going into the ice ages, is conjectured to cause a stepwise increase of climate variability since the early Pliocene.

scholarly journals A theory of glacial cycles: resolving Pleistocene puzzles

2021 ◽  
Author(s):  
Hsien-Wang Ou
Keyword(s):  
Freezing Point ◽  
Surface Air Temperature ◽  
Climate System ◽  
Ice Age ◽  
Early Pleistocene ◽  
Polar Ice ◽  
Glacial Cycles ◽  
Convective Flux ◽  
Ice Volume ◽  
Ice Cap

Abstract. Since the summer surface air temperature that regulates the ice margin is anchored on the sea surface temperature, we posit that the climate system constitutes the intermediary of the orbital forcing of the glacial cycles. As such, the relevant forcing is the annual solar flux absorbed by the ocean, which naturally filters out the precession effect in early Pleistocene but mimics the Milankovitch insolation in late Pleistocene. For a coupled climate system that is inherent turbulent, we show that the ocean may be bistable with a cold state defined by the freezing point subpolar water, which would translate to ice bistates between a polar ice cap and an ice sheet extending to mid-latitudes, enabling large ice-volume signal regardless the forcing amplitude so long as the bistable thresholds are crossed. Such thresholds are set by the global convective flux, which would be lowered during the Pleistocene cooling, whose interplay with the ice-albedo feedback leads to transitions of the ice signal from that dominated by obliquity to the emerging precession cycles to the ice-age cycles paced by eccentricity. Through a single dynamical framework, the theory thus may resolve many long-standing puzzles of the glacial cycles.

scholarly journals On the Milankovitch sensitivity of the Quaternary deep-sea record

2013 ◽  
Vol 9 (4) ◽  
pp. 2003-2011 ◽  
Author(s):  
W. H. Berger
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Climate Variability ◽  
Deep Sea ◽  
Climate System ◽  
Ice Age ◽  
External Forcing ◽  
Orbital Forcing ◽  
System A ◽  
Yield Information

Abstract. The response of the climate system to external forcing (that is, global warming) has become an item of prime interest, especially with respect to the rate of melting of land-based ice masses. The deep-sea record of ice-age climate change has been useful in assessing the sensitivity of the climate system to a different type of forcing; that is, to orbital forcing, which is well known for the last several million years. The expectation is that the response to one type of forcing will yield information about the likely response to other types of forcing. When comparing response and orbital forcing, one finds that sensitivity to this type of forcing varies greatly through time, evidently in dependence on the state of the system and the associated readiness of the system for change. The changing stability of ice masses is here presumed to be the chief underlying cause for the changing state of the system. A buildup of vulnerable ice masses within the latest Tertiary, when going into the ice ages, is thus here conjectured to cause a stepwise increase of climate variability since the early Pliocene.

Predicting regional climate change: living with uncertainty

1999 ◽  
Vol 23 (1) ◽  
pp. 57-78 ◽  
Author(s):  
Timothy D. Mitchell ◽  
Mike Hulme
Keyword(s):  
Climate Change ◽  
Climate Models ◽  
Thermohaline Circulation ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Climate Prediction ◽  
Climate System ◽  
Global System ◽  
Regional Climate Prediction

Regional climate prediction is not an insoluble problem, but it is a problem characterized by inherent uncertainty. There are two sources of this uncertainty: the unpredictability of the climatic and global systems. The climate system is rendered unpredictable by deterministic chaos; the global system renders climate prediction uncertain through the unpredictability of the external forcings imposed on the climate system. It is commonly inferred from the differences between climate models on regional scales that the models are deficient, but climate system unpredictability is such that this inference is premature; the differences are due to an unresolved combination of climate system unpredictability and model deficiencies. Since model deficiencies are discussed frequently and the two sources of inherent uncertainty are discussed only rarely, this review considers the implications of climatic and global system unpredictability for regional climate prediction. Consequently we regard regional climate prediction as a cascade of uncertainty, rather than as a single result process sullied by model deficiencies. We suggest three complementary methodological approaches: (1) the use of multiple forcing scenarios to cope with global system unpredictability; (2) the use of ensembles to cope with climate system unpredictability; and (3) the consideration of the entire response of the climate system to cope with the nature of climate change. We understand regional climate change in terms of changes in the general circulations of the atmosphere and oceans; so we illustrate the role of uncertainty in the task of regional climate prediction with the behaviour of the North Atlantic thermohaline circulation. In conclusion we discuss the implications of the uncertainties in regional climate prediction for research into the impacts of climate change, and we recognize the role of feedbacks in complicating the relatively simple cascade of uncertainties presented here.

scholarly journals Climate Variability in Central Europe during the Last 2500 Years Reconstructed from Four High-Resolution Multi-Proxy Speleothem Records

Geosciences ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 166
Author(s):  
Sarah Waltgenbach ◽  
Dana F. C. Riechelmann ◽  
Christoph Spötl ◽  
Klaus P. Jochum ◽  
Jens Fohlmeister ◽  
...  
Keyword(s):  
Trace Elements ◽  
High Resolution ◽  
Climate Variability ◽  
Little Ice Age ◽  
Medieval Warm Period ◽  
Warm Period ◽  
Ice Age ◽  
Cold Period ◽  
Cave System ◽  
Dark Ages

The Late Holocene was characterized by several centennial-scale climate oscillations including the Roman Warm Period, the Dark Ages Cold Period, the Medieval Warm Period and the Little Ice Age. The detection and investigation of such climate anomalies requires paleoclimate archives with an accurate chronology as well as a high temporal resolution. Here, we present 230Th/U-dated high-resolution multi-proxy records (δ13C, δ18O and trace elements) for the last 2500 years of four speleothems from Bunker Cave and the Herbstlabyrinth cave system in Germany. The multi-proxy data of all four speleothems show evidence of two warm and two cold phases during the last 2500 years, which coincide with the Roman Warm Period and the Medieval Warm Period, as well as the Dark Ages Cold Period and the Little Ice Age, respectively. During these four cold and warm periods, the δ18O and δ13C records of all four speleothems and the Mg concentration of the speleothems Bu4 (Bunker Cave) and TV1 (Herbstlabyrinth cave system) show common features and are thus interpreted to be related to past climate variability. Comparison with other paleoclimate records suggests a strong influence of the North Atlantic Oscillation at the two caves sites, which is reflected by warm and humid conditions during the Roman Warm Period and the Medieval Warm Period, and cold and dry climate during the Dark Ages Cold period and the Little Ice Age. The Mg records of speleothems Bu1 (Bunker Cave) and NG01 (Herbstlabyrinth) as well as the inconsistent patterns of Sr, Ba and P suggests that the processes controlling the abundance of these trace elements are dominated by site-specific effects rather than being related to supra-regional climate variability.

scholarly journals Role of Biochar in Improving Sandy Soil Water Retention and Resilience to Drought

Water ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 407
Author(s):  
Ling Li ◽  
Yong-Jiang Zhang ◽  
Abigayl Novak ◽  
Yingchao Yang ◽  
Jinwu Wang
Keyword(s):  
Climate Variability ◽  
Sandy Soil ◽  
Water Retention ◽  
Sandy Soils ◽  
Crop Productivity ◽  
Future Research ◽  
Soil Water Retention ◽  
The World ◽  
Water Holding

In recent years, plants in sandy soils have been impacted by increased climate variability due to weak water holding and temperature buffering capacities of the parent material. The projected impact spreads all over the world, including New England, USA. Many regions of the world may experience an increase in frequency and severity of drought, which can be attributed to an increased variability in precipitation and enhanced water loss due to warming. The overall benefits of biochar in environmental management have been extensively investigated. This review aims to discuss the water holding capacity of biochar from the points of view of fluid mechanics and propose several prioritized future research topics. To understand the impacts of biochar on sandy soils in-depth, sandy soil properties (surface area, pore size, water properties, and characteristics) and how biochar could improve the soil quality as well as plant growth, development, and yield are reviewed. Incorporating biochar into sandy soils could result in a net increase in the surface area, a stronger hydrophobicity at a lower temperature, and an increase in the micropores to maximize gap spaces. The capability of biochar in reducing fertilizer drainage through increasing water retention can improve crop productivity and reduce the nutrient leaching rate in agricultural practices. To advance research in biochar products and address the impacts of increasing climate variability, future research may focus on the role of biochar in enhancing soil water retention, plant water use efficiency, crop resistance to drought, and crop productivity.

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