West Asian climate during the last millennium according to the EC-Earth model

2020 ◽  
Vol 57 (1) ◽  
pp. 102-113
Author(s):  
M.P. Karami ◽  
M. Mohtadi ◽  
Q. Zhang ◽  
T. Koenigk
Keyword(s):  
Decadal Variability ◽  
Ice Age ◽  
Earth Model ◽  
Precipitation Trend ◽  
Last Millennium ◽  
Climate Trends ◽  
The Caspian Sea ◽  
Internal Climate Variability ◽  
The North ◽  
The Impact

West Asia is one of the most vulnerable regions to ongoing climate change but has been poorly investigated. Therefore, it is crucial to understand the impact of anthropogenic greenhouse gas, natural forcing, and internal climate variability on temperature and rainfall in this region. In this study, we focus on the climate of West Asia during the last millennium by using a transient simulation of the global earth system model EC-Earth (v3.1). The model performs well in terms of present-day temperature and precipitation patterns and their regional averages. Time series of yearly-mean precipitation and temperature of West Asia show that precipitation increases until the start of the Little Ice Age (1450–1850 CE) and subsequently decreases, whereas temperature shows a cooling trend during the entire last millennium. We first discuss the model output data for climate trends during two periods, 850–1450 CE and 1450–1850 CE. In 850–1450 CE, the largest wetting trend occurred in the eastern regions to the north of the Persian Gulf because of a westward shift of the Indian precipitation core and more moisture transport from the Arabian Sea. The precipitation trend in 1450–1850 CE had a different pattern with a drying trend in the west of the Caspian Sea and overall getting less wet compared with the first period. Temperature showed cooling trends for both periods with the largest values happening in the northern regions. The North Atlantic sea surface temperature cooling and the subsequent change in atmospheric circulation played a role in the wetting and cooling of West Asia. In the second part of the study, we remove the trends and discuss the multi-decadal variability of West Asian climate. It was found that Atlantic multi-decadal and Pacific decadal oscillations strongly contributed to West Asian temperature variability. For West Asian precipitation variability, we found remote connections with the Nordic seas and tropical Pacific Ocean.

scholarly journals INTERRELATION OF GEOPHYSICAL FIELDS CYCLIC VARIATIONS WITH THE TIDAL DEFORMATIONS ACTION ACCORDING TO THE NPEMFE OBSERVATIONAL DATA IN THE NORTH-CAUCASIAN SEISMOACTIVE REGION ANALYSIS

2016 ◽  
Author(s):  
Д.Н. Забирченко ◽  
Л.Л. Круткин
Keyword(s):  
The Black Sea ◽  
North Caucasus ◽  
The Caspian Sea ◽  
Geophysical Fields ◽  
Caucasus Region ◽  
The North ◽  
Cyclic Variations ◽  
Pulsed Electromagnetic ◽  
Tidal Deformations ◽  
The Impact

В результате анализа многолетних рядов наблюдений за естественным импульсным электромагнитным полем Земли (ЕИЭМПЗ или ЭМИ) по сети из 10 регистраторов, расположенных от Черного до Каспийского моря в пределах сейсмоопасных районов Северо-Кавказского региона, выделены характерные особенности поведения суточных и сезонных вариаций геофизических полей. Проведен анализ взаимосвязи вариаций ЭМИ с воздействием лунно-солнечных приливных деформаций An analysis of long-term series of observations of the natural pulsed electromagnetic field of the Earth in a network of 10 registrars, located on the Black Sea to the Caspian Sea within the seismic areas of the North Caucasus region, marked characteristic regional features of the behavior of diurnal and seasonal variations of geophysical fields. An analysis of the relationship of variations with the impact of lunisolar tidal deformation

scholarly journals Holocene hydrological changes in the Rhône River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Vol 12 (7) ◽  
pp. 1539-1553 ◽  
Author(s):  
Maria-Angela Bassetti ◽  
Serge Berné ◽  
Marie-Alexandrine Sicre ◽  
Bernard Dennielou ◽  
Yoann Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are the most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea–land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m long sediment core from the Rhône mud belt in the Gulf of Lions in an area where the average accumulation rate is ca. 0.70 m 1000 yr−1. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multiproxy dataset (XRF core scan, 14C dates, grain size and organic-matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes in the Rhône hydrological activity. Our results show that (1) the early Holocene was characterized by high sediment delivery likely indicative of local intense (but short-duration) rainfall events, (2) important sediment delivery around 7 ka cal BP presumably related to increased river flux, (3) a progressive increase in continental/marine input during the mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, (4) multidecadal to centennial humid events took place in the late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Ages Cold Period) and also coincide with time intervals of major floods in the northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

scholarly journals An explicit estimate of the atmospheric nutrient impact on global oceanic productivity

Ocean Science ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1183-1205
Author(s):  
Stelios Myriokefalitakis ◽  
Matthias Gröger ◽  
Jenny Hieronymus ◽  
Ralf Döscher
Keyword(s):  
Ocean Model ◽  
Global Ocean ◽  
Earth Model ◽  
Nutrient Inputs ◽  
Deposition Fluxes ◽  
Nutrient Deposition ◽  
The North ◽  
Atmospheric Forcings ◽  
Substantial Decline ◽  
The Impact

Abstract. State-of-the-art global nutrient deposition fields are coupled here to the Pelagic Interactions Scheme for Carbon and Ecosystem Studies (PISCES) biogeochemistry model to investigate their effect on ocean biogeochemistry in the context of atmospheric forcings for pre-industrial, present, and future periods. PISCES, as part of the European Community Earth system model (EC-Earth) model suite, runs in offline mode using prescribed dynamical fields as simulated by the Nucleus for European Modelling of the Ocean (NEMO) ocean model. Present-day atmospheric deposition fluxes of inorganic N, Fe, and P into the global ocean account for ∼ 40 Tg N yr−1, ∼ 0.28 Tg Fe yr−1, and ∼ 0.10 Tg P yr−1. Pre-industrial atmospheric nutrient deposition fluxes are lower compared to the present day (∼ 51 %, ∼ 36 %, and ∼ 40 % for N, Fe, and P, respectively). However, the overall impact on global productivity is low (∼ 3 %) since a large part of marine productivity is driven by nutrients recycled in the upper ocean layer or other local factors. Prominent changes are, nevertheless, found for regional productivity. Reductions of up to 20 % occur in oligotrophic regions such as the subtropical gyres in the Northern Hemisphere under pre-industrial conditions. In the subpolar Pacific, reduced pre-industrial Fe fluxes lead to a substantial decline of siliceous diatom production and subsequent accumulation of Si, P, and N, in the subpolar gyre. Transport of these nutrient-enriched waters leads to strongly elevated production of calcareous nanophytoplankton further south and southeast, where iron no longer limits productivity. The North Pacific is found to be the most sensitive to variations in depositional fluxes, mainly because the water exchange with nutrient-rich polar waters is hampered by land bridges. By contrast, large amounts of unutilized nutrients are advected equatorward in the Southern Ocean and North Atlantic, making these regions less sensitive to external nutrient inputs. Despite the lower aerosol N : P ratios with respect to the Redfield ratio during the pre-industrial period, the nitrogen fixation decreased in the subtropical gyres mainly due to diminished iron supply. Future changes in air pollutants under the Representative Concentration Pathway 8.5 (RCP8.5) emission scenario result in a modest decrease of the atmospheric nutrients inputs into the global ocean compared to the present day (∼ 13 %, ∼ 14 %, and ∼ 20 % for N, Fe, and P, respectively), without significantly affecting the projected primary production in the model. Sensitivity simulations further show that the impact of atmospheric organic nutrients on the global oceanic productivity has turned out roughly as high as the present-day productivity increase since the pre-industrial era when only the inorganic nutrients' supply is considered in the model. On the other hand, variations in atmospheric phosphorus supply have almost no effect on the calculated oceanic productivity.

Bivalves indicate that the North Atlantic was under stress before the onset of the Little Ice Age

2021 ◽  
Author(s):  
Beatriz Arellano Nava ◽  
Paul R. Halloran ◽  
Chris A. Boulton ◽  
Timothy M. Lenton
Keyword(s):  
Marine Environment ◽  
North Atlantic ◽  
Little Ice Age ◽  
Stable State ◽  
Volcanic Eruptions ◽  
Ice Age ◽  
Last Millennium ◽  
The North ◽  
Growth Increments ◽  
Negative Feedbacks

<p>The last millennium was characterised by a cooling from the Medieval Warm Period into the Little Ice Age. While strong volcanic eruptions could have triggered the onset of the Little Ice Age by reducing solar irradiance, modelling experiments suggest that it was amplified and maintained by sea ice-ocean feedbacks, including a potential abrupt weakening of the subpolar gyre. The weakening of negative feedbacks that maintain a system in a stable state, prior to an abrupt transition, can be detected as an increase in temporal autocorrelation and variability. Here we use an annually-resolved and absolutely dated shell-derived record from the North Icelandic Shelf that spans the last millennium, to detect such a loss of resilience in the marine environment leading up to the Little Ice Age transition. We find a significant increase in autocorrelation and variance in bivalve growth increments and oxygen isotopes before the transition, providing evidence consistent with loss of stability in the marine environment. This supports the idea that internal feedbacks played an important role in the Little Ice Age onset.</p>

Trends, Variability and Predictive Skill of the Ocean Heat Content in North Atlantic: An Analysis with the EC-Earth3 Model

2021 ◽  
Author(s):  
Teresa Carmo-Costa ◽  
Roberto Bilbao ◽  
Pablo Ortega ◽  
Ana Teles-Machado ◽  
Emanuel Dutra
Keyword(s):  
North Atlantic ◽  
Climate Model ◽  
Decadal Variability ◽  
Heat Content ◽  
Internal Variability ◽  
Ocean Heat Content ◽  
Internal Climate Variability ◽  
The North ◽  
Predictive Skill ◽  
Modeling Uncertainties

Abstract This study investigates trends, variability and predictive skill of the upper ocean heat content (OHC) in the North Atlantic basin. This is a region where strong decadal variability superimposes the externally forced trends, introducing important differences in the local warming rates, and leading in the case of the Central Subpolar North Atlantic to an overall long-term cooling. Our analysis aims to better understand these regional differences, by investigating how internal and forced variability contribute to local trends, exploring also their role on the local prediction skill. The analysis combines the study of three ocean reanalyses to document the uncertainties related to observations, with two sets of CMIP6 experiments performed with the global coupled climate model EC-Earth3: a historical ensemble to characterise the forced signals; and a retrospective decadal prediction system, to additionally characterise the contributions from internal climate variability. Our results show that internal variability is essential to understand the spatial pattern of North Atlantic OHC trends, contributing decisively to the local trends and providing high levels of predictive skill in the Eastern Subpolar North Atlantic and the Irminger and Iceland Seas, and to a lesser extent in the Labrador Sea. Skill and trends in other areas like the Subtropical North Atlantic, or the Gulf Stream Extension are mostly externally forced. Large observational and modeling uncertainties affect the trends and interannual variability in the Central Subpolar North Atlantic, the only region exhibiting a cooling during the study period, uncertainties that might explain the very poor local predictive skill.

scholarly journals Neoglacial trends in diatom dynamics from a small alpine lake in the Qinling mountains of central China

2020 ◽  
Vol 16 (2) ◽  
pp. 543-554
Author(s):  
Bo Cheng ◽  
Jennifer Adams ◽  
Jianhui Chen ◽  
Aifeng Zhou ◽  
Qing Zhang ◽  
...  
Keyword(s):  
Decadal Variability ◽  
Asian Summer Monsoon ◽  
Central China ◽  
Ice Age ◽  
Qinling Mountains ◽  
Alpine Regions ◽  
Low Profile ◽  
Community Restructuring ◽  
Asian Summer ◽  
The Impact

Abstract. During the latter stages of the Holocene, and prior to anthropogenic global warming, the Earth underwent a period of cooling called the neoglacial. The neoglacial is associated with declining summer insolation and changes to Earth's surface albedo. Although impacts varied globally, in China the neoglacial was generally associated with a cooler climate and an attenuated Asian summer monsoon. Few studies in central China, however, have explored the impact of neoglacial cooling on freshwater diversity, especially in alpine regions. Here we take a palaeolimnological approach to characterise multi-decadal variability in diatom community composition, ecological guilds, and compositional turnover over the past 3500 years from the alpine Yuhuang Chi lake on Mount Taibai in the Qinling mountains. Diatoms in the high-profile guild dominate much of the record from 3500 to 615 cal BP, which suggests that few nutrients in the lake were limiting overall, and disturbance and herbivory were likely low. After 615 cal BP, low-profile and planktic guild diatoms increase, suggesting greater turbulence in the lake, alongside a decline in available nutrients. Diatom turnover highlights periods in the lake history when deterministic processes structured diatom communities. For example, an abrupt decline in turnover is coincident with the shift from high- to low-profile diatoms at 615 cal BP, and this is likely due to the onset of the Little Ice Age in the region. We suggest that Yuhuang Chi lake became more shallow during peak regional aridity, which led to the short-lived community restructuring observed in the record.

scholarly journals Influence of solar variability, CO<sub>2</sub> and orbital forcing between 1000 and 1850 AD in the IPSLCM4 model

2010 ◽  
Vol 6 (4) ◽  
pp. 445-460 ◽  
Author(s):  
J. Servonnat ◽  
P. Yiou ◽  
M. Khodri ◽  
D. Swingedouw ◽  
S. Denvil
Keyword(s):  
Climate Model ◽  
Internal Variability ◽  
Temperature Reconstruction ◽  
Temperature Variability ◽  
Ice Age ◽  
Last Millennium ◽  
Orbital Forcing ◽  
Temperature Reconstructions ◽  
Temperature Signal ◽  
The Impact

Abstract. Studying the climate of the last millennium gives the possibility to deal with a relatively well-documented climate essentially driven by natural forcings. We have performed two simulations with the IPSLCM4 climate model to evaluate the impact of Total Solar Irradiance (TSI), CO2 and orbital forcing on secular temperature variability during the preindustrial part of the last millennium. The Northern Hemisphere (NH) temperature of the simulation reproduces the amplitude of the NH temperature reconstructions over the last millennium. Using a linear statistical decomposition we evaluated that TSI and CO2 have similar contributions to secular temperature variability between 1425 and 1850 AD. They generate a temperature minimum comparable to the Little Ice Age shown by the temperature reconstructions. Solar forcing explains ~80% of the NH temperature variability during the first part of the millennium (1000–1425 AD) including the Medieval Climate Anomaly (MCA). It is responsible for a warm period which occurs two centuries later than in the reconstructions. This mismatch implies that the secular variability during the MCA is not fully explained by the response of the model to the TSI reconstruction. With a signal-noise ratio (SNR) estimate we found that the temperature signal of the forced simulation is significantly different from internal variability over area wider than ~5.106 km2, i.e. approximately the extent of Europe. Orbital forcing plays a significant role in latitudes higher than 65° N in summer and supports the conclusions of a recent study on an Arctic temperature reconstruction over past two millennia. The forced variability represents at least half of the temperature signal on only ~30% of the surface of the globe. This study suggests that regional reconstructions of the temperature between 1000 and 1850 AD are likely to show weak signatures of solar, CO2 and orbital forcings compared to internal variability.

scholarly journals Holocene hydrological changes of the Rhone River (NW Mediterranean) as recorded in the marine mud belt

2016 ◽  
Author(s):  
M. A. Bassetti ◽  
S. Berné ◽  
M. A. Sicre ◽  
B. Dennielou ◽  
Y. Alonso ◽  
...  
Keyword(s):  
North Atlantic ◽  
Accumulation Rate ◽  
Sediment Accumulation ◽  
Progressive Increase ◽  
Ice Age ◽  
Sediment Delivery ◽  
The North ◽  
Catchment Areas ◽  
The North Atlantic ◽  
The Impact

Abstract. Expanded marine Holocene archives are relatively scarce in the Mediterranean Sea because most of the sediments were trapped in catchment areas during this period. Mud belts are most suitable targets to access expanded Holocene records. These sedimentary bodies represent excellent archives for the study of sea-land interactions and notably the impact of the hydrological activity on sediment accumulation. We retrieved a 7.2 m-long sediment core from the Rhone mud belt in the Gulf of Lions in an area where the average accumulation rate is of ca. 0.70 m/1000 years. This core thus provides a continuous and high-resolution record of the last 10 ka cal BP. A multi-proxy dataset (XRF-core scan, 14C dates, grain size and organic matter analysis) combined with seismic stratigraphic analysis was used to document decadal to centennial changes of the Rhone hydrological activity. Our results show that 1) the Early Holocene was characterized by high sediment delivery likely indicative of local intense (but short duration) rainfall events , 2) important sediment delivery around 7 ka cal BP roughly presumably related to increased river flux, 3) a progressive increase of continental/marine input during the Mid-Holocene despite increased distance from river outlets due to sea-level rise possibly related to higher atmospheric humidity caused by the southward migration of the storm tracks in the North Atlantic, 4) multi-decadal to centennial humid events in the Late Holocene. Some of these events correspond to the cold periods identified in the North Atlantic (Little Ice Age, LIA; Dark Age) and also coincide with time intervals of major floods a in the Northern Alps. Other humid events are also observed during relatively warm periods (Roman Humid Period and Medieval Climate Anomaly).

scholarly journals Decadal Variability in the Impact of Atmospheric Circulation Patterns on the Winter Climate of Northern Russia

2021 ◽  
Vol 34 (3) ◽  
pp. 1005-1021
Author(s):  
Gareth J. Marshall
Keyword(s):  
Atmospheric Circulation ◽  
Decadal Variability ◽  
The Arctic ◽  
Temporal Consistency ◽  
Atmospheric Circulation Patterns ◽  
The North ◽  
Dominant Pattern ◽  
Circulation Patterns ◽  
Northern Russia ◽  
The Impact

AbstractThe Arctic continues to warm at a much faster rate than the global average. One process contributing to “Arctic amplification” involves changes in low-frequency macroscale atmospheric circulation patterns and their consequent influence on regional climate. Here, using ERA5 data, we examine decadal changes in the impact of seven such patterns on winter near-surface temperature (SAT) and precipitation (PPN) in northern Russia and calculate the temporal consistency of any statistically significant relationships. We demonstrate that the 40-yr climatology hides considerable decadal variability in the spatial extent of such circulation pattern–climate relationships across the region, with few areas where their temporal consistency exceeds 60%. This is primarily a response to the pronounced decadal expansion/contraction and/or mobility of the circulation patterns’ centers of action. The North Atlantic Oscillation (NAO) is the dominant pattern (having the highest temporal consistency) affecting SAT west of the Urals. Farther east, the Scandinavian (SCA), Polar/Eurasian (POL), and West Pacific patterns are successively the dominant pattern influencing SAT across the West Siberian Plains, Central Siberian Plateau, and mountains of Far East Siberia, respectively. From west to east, the SCA, POL, and Pacific–North American patterns exert the most consistent decadal influence on PPN. The only temporally invariant significant decadal relationships occur between the NAO and SAT and the SCA and PPN in small areas of the North European Plain.

scholarly journals Interannual to Decadal Variations of Submesoscale Motions around the North Pacific Subtropical Countercurrent

Fluids ◽  
2020 ◽  
Vol 5 (3) ◽  
pp. 116
Author(s):  
Hideharu Sasaki ◽  
Bo Qiu ◽  
Patrice Klein ◽  
Yoshikazu Sasai ◽  
Masami Nonaka
Keyword(s):  
Mixed Layer ◽  
Decadal Variability ◽  
Mixed Layer Depth ◽  
Northwestern Pacific ◽  
The North ◽  
Subtropical Countercurrent ◽  
The Pacific ◽  
Decadal Variations ◽  
The Impact ◽  
The North Pacific

The outputs from a submesoscale permitting hindcast simulation from 1990 to 2016 are used to investigate the interannual to decadal variations of submesoscale motions. The region we focus on is the subtropical Northwestern Pacific including the subtropical countercurrent. The submesoscale kinetic energy (KE) is characterized by strong interannual and decadal variability, displaying larger magnitudes in 1996, 2003, and 2015, and smaller magnitudes in 1999, 2009, 2010, and 2016. These variations are partially explained by those of the available potential energy (APE) release at submesoscale driven by mixed layer instability in winter. Indeed, this APE release depends on the mixed layer depth and horizontal buoyancy gradient, both of them modulated with the Pacific Decadal Oscillation (PDO). As a result of the inverse KE cascade, the submesoscale KE variability possibly leads to interannual to decadal variations of the mesoscale KE (eddy KE (EKE)). These results show that submesoscale motions are a possible pathway to explain the impact associated with the PDO on the decadal EKE variability. The winter APE release estimated from the Argo float observations varies synchronously with that in the simulation on the interannual time scales, which suggests the observation capability to diagnose the submesoscale KE variability.

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