scholarly journals High-resolution marine data and transient simulations support orbital forcing of ENSO amplitude since the mid-Holocene

2021 ◽  
Vol 268 ◽  
pp. 107125
Author(s):  
Matthieu Carré ◽  
Pascale Braconnot ◽  
Mary Elliot ◽  
Roberta d’Agostino ◽  
Andrew Schurer ◽  
...  
Keyword(s):  
High Resolution ◽  
Orbital Forcing ◽  
Transient Simulations ◽  
Marine Data

scholarly journals Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

2011 ◽  
Vol 7 (5) ◽  
pp. 3609-3652 ◽  
Author(s):  
J. H. C. Bosmans ◽  
S. S. Drijfhout ◽  
E. Tuenter ◽  
L. J. Lourens ◽  
F. J. Hilgen ◽  
...  
Keyword(s):  
High Resolution ◽  
North Africa ◽  
Climate Model ◽  
South American ◽  
Orbital Forcing ◽  
Model Studies ◽  
Summer Insolation ◽  
Moisture Advection ◽  
Monsoonal Precipitation ◽  
Monsoon Winds

Abstract. In this study we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.

scholarly journals Monsoonal response to mid-holocene orbital forcing in a high resolution GCM

2012 ◽  
Vol 8 (2) ◽  
pp. 723-740 ◽  
Author(s):  
J. H. C. Bosmans ◽  
S. S. Drijfhout ◽  
E. Tuenter ◽  
L. J. Lourens ◽  
F. J. Hilgen ◽  
...  
Keyword(s):  
High Resolution ◽  
North Africa ◽  
Climate Model ◽  
South American ◽  
Orbital Forcing ◽  
Model Studies ◽  
Summer Insolation ◽  
Moisture Advection ◽  
Monsoonal Precipitation ◽  
Monsoon Winds

Abstract. In this study, we use a sophisticated high-resolution atmosphere-ocean coupled climate model, EC-Earth, to investigate the effect of Mid-Holocene orbital forcing on summer monsoons on both hemispheres. During the Mid-Holocene (6 ka), there was more summer insolation on the Northern Hemisphere than today, which intensified the meridional temperature and pressure gradients. Over North Africa, monsoonal precipitation is intensified through increased landward monsoon winds and moisture advection as well as decreased moisture convergence over the oceans and more convergence over land compared to the pre-industrial simulation. Precipitation also extends further north as the ITCZ shifts northward in response to the stronger poleward gradient of insolation. This increase and poleward extent is stronger than in most previous ocean-atmosphere GCM simulations. In north-westernmost Africa, precipitation extends up to 35° N. Over tropical Africa, internal feedbacks completely overcome the direct warming effect of increased insolation. We also find a weakened African Easterly Jet. Over Asia, monsoonal precipitation during the Mid-Holocene is increased as well, but the response is different than over North-Africa. There is more convection over land at the expense of convection over the ocean, but precipitation does not extend further northward, monsoon winds over the ocean are weaker and the surrounding ocean does not provide more moisture. On the Southern Hemisphere, summer insolation and the poleward insolation gradient were weaker during the Mid-Holocene, resulting in a reduced South American monsoon through decreased monsoon winds and less convection, as well as an equatorward shift in the ITCZ. This study corroborates the findings of paleodata research as well as previous model studies, while giving a more detailed account of Mid-Holocene monsoons.

High-Resolution Marine Data and Interpretation

1979 ◽  
Author(s):  
L.J. Leonard ◽  
B.R. Pottorf ◽  
M.W. Schramm
Keyword(s):  
High Resolution ◽  
Marine Data

External and internal forcing of African Humid Periods from MIS 6 to MIS 1

2021 ◽  
Author(s):  
Mateo Duque-Villegas ◽  
Martin Claussen ◽  
Victor Brovkin ◽  
Thomas Kleinen
Keyword(s):  
Land Surface ◽  
Climate Model ◽  
Ice Sheets ◽  
Recent Sediment ◽  
Orbital Forcing ◽  
Atmospheric Concentration ◽  
Vegetation Growth ◽  
Orbital Parameters ◽  
Transient Simulations ◽  
The Individual

<p>During the last million years, northern Africa has alternated between arid and humid conditions, as recorded by different kinds of climate archives, including fossil pollen, lake sediments, marine sediments and archaeological remains. Variations occur at millennial scale, with dry phases being similar to the current desert state in the region, and with wet phases, known as African Humid Periods (AHPs), characterised by a strong summer monsoon which can carry enough moisture inland to support rivers, lakes and lush vegetation further north than seen today. Recent sediment records from the Mediterranean Sea revealed that the previous five AHPs had different intensities, in relation to rainfall and vegetation extent. Motivated by these findings, our work focuses on explaining what caused such differences in intensity. To this end, we use the CLIMBER-2 climate model to study the AHP response to changes in three drivers of atmospheric dynamics: Earth's orbit variations, atmospheric concentration of CO<sub>2</sub> and inland ice extent. Global transient simulations of the last 190,000 years are used in new factorisation analyses, which allow us to separate the individual contributions of the forcings to the AHP intensity, as well as those of their synergies. We confirm the predominant role of the orbital forcing in the strength of the last five AHPs, and our simulations agree with previous estimates of a threshold in orbital forcing above which an AHP develops. Moreover, we show that atmospheric CO<sub>2</sub> and the extent of ice sheets can also add up to be as important as the orbital parameters. High values of CO<sub>2</sub>, past a 205 ppm threshold, and low values of ice sheets extent, below an 8 % of global land surface threshold, yield the AHPs with the most precipitation and vegetation. Additionally, our results show that AHPs differ not only in amplitude, but also in their speed of change, and we find that the non-linear vegetation response of AHPs does not correlate with a single forcing and that the vegetation growth response is faster than its subsequent decline. In regards to future change, an extension of the simulations until the next 50,000 years, shows CO<sub>2</sub> to be the main driver of AHPs, with orbital forcing only setting the pace and their intensities being scenario-dependent.</p>

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.

Monitoring and forecasting of marine pollution in the Mediterranean Sea: the ODYSSEA project approach

2020 ◽  
Author(s):  
Katerina Spanoudaki ◽  
Nikolaos Kokkos ◽  
Konstantinos Zachopoulos ◽  
Georgios Sylaios ◽  
Nikolaos Kampanis ◽  
...  
Keyword(s):  
Water Quality ◽  
High Resolution ◽  
Mediterranean Sea ◽  
Oil Spill ◽  
Mediterranean Basin ◽  
Shelf Zone ◽  
Forecasting System ◽  
Marine Data ◽  
The Mediterranean ◽  
The Mediterranean Basin

<p>The H2020 funded project ODYSSEA (http://odysseaplatform.eu/) aims to make Mediterranean marine data easily accessible and operational to a broad range of users of the marine space. ODYSSEA develops an interoperable and cost-effective platform, fully integrating networks of observing and forecasting systems across the Mediterranean basin, addressing both the open sea and the coastal zone. The platform integrates marine data from existing Earth Observing Systems, such as Copernicus and EMODnet, receives and processes novel, newly produced datasets (through high-resolution models and on-line sensors such as a novel microplastics sensor) from nine prototype Observatories established across the Mediterranean basin, and applies advanced algorithms to organise, homogenise and fuse the large quantities of data in order to provide to various end-user groups and stakeholders both primary data and on-demand derived data services.</p><p>The nine ODYSSEA Observatories are established across the whole Mediterranean basin, covering also areas of marine data gaps along the North African and Middle East coastline. The Observatories comprise observing and forecasting systems and cover coastal and shelf zone environments, Marine Protected Areas and areas with increased human pressure. The operational forecasting system of the Observatories consists of a ‘chain’ of dynamically coupled, high-resolution numerical models comprised of a) the hydrodynamic model Delft3D-FLOW, b) the wave model Delft3D-WAVE (SWAN), c) the water quality model DELWAQ, d) the oil spill fate and transport model MEDSLIK-II, e) the ecosystem model ECOPATH, and f) the in-house mussel farm model developed by the Democritus University of Thrace. This operational system provides forecasts, early warnings and alerts for currents, waves, water quality parameters, oil spill pollution and ecosystem status. In this work, the ODYSSEA forecasting system (developed with the Delft-FEWS software) is implemented for simulating oil spill pollution for the Thracian Sea Observatory.  The area is biodiversity rich and an important spawning and nursery ground for small pelagic species, while in Kavala Gulf, oil exploitation takes place. The Lagrangian oil spill model MEDSLIK-II has been coupled to high-resolution oceanographic fields (currents, temperature, Stokes drift velocity), produced by Delft3D-FLOW and SWAN, and NOAA GFS atmospheric forcing. The hydrodynamic and wave models have been configured for the Thracian Sea based on dynamic downscaling of CMEMS products to a grid resolution of 1/120°. Seasonal hazard maps (surface oil slick, beached oil) are produced employing multiple oil spill scenarios using multi-year hydrodynamics. The results highlight the hazard faced by Thracian Sea Observatory coasts. </p><p><strong>Acknowledgements:</strong> This research has received funding from the European Union’s Horizon 2020 research and innovation programme ODYSSEA: OPERATING A NETWORK OF INTEGRATED OBSERVATORY SYSTEMS IN THE MEDITERRANEAN SEA, GA No 72727.</p>

scholarly journals Optimal full-waveform inversion strategy for marine data in azimuthally rotated elastic orthorhombic media

Geophysics ◽  
2018 ◽  
Vol 83 (4) ◽  
pp. R307-R320 ◽  
Author(s):  
Ju-Won Oh ◽  
Tariq Alkhalifah
Keyword(s):  
High Resolution ◽  
Reservoir Characterization ◽  
Waveform Inversion ◽  
Horizontal Layer ◽  
Full Waveform Inversion ◽  
Radiation Patterns ◽  
Trade Off ◽  
Full Waveform ◽  
Gradient Direction ◽  
Marine Data

The orthorhombic (ORT) anisotropic description of earth layers can allow the capture of much of the earth’s anisotropic complexity. The inversion for high-resolution azimuthal variation of anisotropy is important for reservoir characterization, among other applications. A high-resolution description of the azimuth of fractures can help us to predict flow preferences. To verify the feasibility of multiparameter full-waveform inversion (FWI) for marine data assuming azimuthally rotated elastic ORT media, we have analyzed the radiation patterns and gradient directions of ORT parameters to the reflection data. First, we express the gradient direction of the ORT parameters considering the azimuthal rotation of the symmetric planes. Then, to support our observations in the gradient direction, the radiation patterns of the partial derivative wavefields from each parameter perturbation are also derived under the rotated elastic ORT assumption. To find an optimal parameterization, we compare three different parameterizations: monoclinic, velocity-based, and hierarchical parameterizations. Then, we suggest an optimal multistage update strategy by analyzing the behavior of the rotation angle as a FWI target. To analyze the trade-off among parameters in different parameterizations, we calculate the gradient direction from a hockey-puck model, in which each parameter is perturbed at the different location on a horizontal layer. The trade-off analysis supports that the hierarchical parameterization provides us with more opportunities to build up subsurface models with less trade-off between parameters and less influence of the azimuthal rotation of ORT anisotropy. The feasibility of the proposed FWI strategy is examined using synthetic marine streamer data from a simple 3D reservoir model with a fractured layer.

scholarly journals Holocene evolution of the Southern Hemisphere westerly winds in transient simulations with global climate models

2011 ◽  
Vol 7 (3) ◽  
pp. 1797-1824 ◽  
Author(s):  
V. Varma ◽  
M. Prange ◽  
U. Merkel ◽  
T. Kleinen ◽  
G. Lohmann ◽  
...  
Keyword(s):  
Southern Hemisphere ◽  
Climate Models ◽  
Climate Model ◽  
Global Climate ◽  
Global Climate Model ◽  
Global Climate Models ◽  
Orbital Forcing ◽  
Westerly Winds ◽  
Transient Simulations ◽  
Southern Hemisphere Westerly Winds

Abstract. The Southern Hemisphere Westerly Winds (SWW) have been suggested to exert a critical influence on global climate through wind-driven upwelling of deep water in the Southern Ocean and the potentially resulting atmospheric CO2 variations. The investigation of the temporal and spatial evolution of the SWW along with forcings and feedbacks remains a significant challenge in climate research. In this study, the evolution of the SWW under orbital forcing from the mid-Holocene (7 kyr BP) to pre-industrial modern times (250 yr BP) is examined with transient experiments using the comprehensive coupled global climate model CCSM3. In addition, a model inter-comparison is carried out using orbitally forced Holocene transient simulations from four other coupled global climate models. Analyses and comparison of the model results suggest that the annual and seasonal mean SWW were subject to an overall strengthening and poleward shifting trend during the course of the mid-to-late Holocene under the influence of orbital forcing, except for the austral spring season, where the SWW exhibited an opposite trend of shifting towards the equator.

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