scholarly journals Reconstruction of southeast Tibetan Plateau summer cloud cover over the past two centuries using tree ring δ<sup>18</sup>O

2011 ◽  
Vol 7 (3) ◽  
pp. 1825-1844 ◽  
Author(s):  
C. Shi ◽  
V. Daux ◽  
C. Risi ◽  
S.-G. Hou ◽  
M. Stievenard ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Tree Ring ◽  
Volcanic Eruption ◽  
General Circulation ◽  
Cloud Cover ◽  
Circulation Model ◽  
Ice Cores ◽  
Strongly Correlated ◽  
The Past ◽  
Southeast Tibetan Plateau

Abstract. A tree-ring δ18O chronology of Linzhi spruce, spanning from AD 1781 to 2005, was developed in Bomi, Southeast Tibetan Plateau (TP). During the period with instrumental data (1961–2005), this record is strongly correlated with regional summer cloud cover, which is supported by a precipitation δ18O simulation conducted with the isotope-enabled atmospheric general circulation model LMDZiso. A 225-yr regional cloud cover reconstruction was therefore achieved. The observed cloud cover increased in the 1980s and this increase is not unprecedented in the entire reconstruction. The reconstructed cloud cover appears smaller and more stable in the 20th century than previously. A late 19th century decrease in our reconstructed cloud cover is consistent with a decrease in the TP glacier accumulation recorded in ice cores. Our data reveal a strong anomaly in the 1810s, which coincides with volcanic eruption in 1809 and the 1815 Tambora volcanic eruption.

scholarly journals Reconstruction of southeast Tibetan Plateau summer climate using tree ring δ<sup>18</sup>O: moisture variability over the past two centuries

2012 ◽  
Vol 8 (1) ◽  
pp. 205-213 ◽  
Author(s):  
C. Shi ◽  
V. Daux ◽  
Q.-B. Zhang ◽  
C. Risi ◽  
S.-G. Hou ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Tree Ring ◽  
General Circulation ◽  
Empirical Relationship ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
The Past ◽  
The Impact ◽  
Southeast Tibetan Plateau ◽  
Moisture Variability

Abstract. A tree-ring δ18O chronology of Linzhi spruce, spanning from AD 1781 to 2005, was developed in Bomi, Southeast Tibetan Plateau (TP). During the period with instrumental data (AD 1961–2005), this record is strongly correlated with regional CRU (Climate Research Unit) summer cloud data, which is supported by a precipitation δ18O simulation conducted with the isotope-enabled atmospheric general circulation model LMDZiso. A reconstruction of a regional summer cloud index, based upon the empirical relationship between cloud and diurnal temperature range, was therefore achieved. This index reflects regional moisture variability in the past 225 yr. The climate appears drier and more stable in the 20th century than previously. The drying trend in late 19th century of our reconstruction is consistent with a decrease in the TP glacier accumulation recorded in ice cores. An exceptional dry decade is documented in the 1810s, possibly related to the impact of repeated volcanic eruptions on monsoon flow.

scholarly journals Comprendre la dynamique atmosphérique pour mieux reconstituer l'altitude passée des chaînes de montagnes

2020 ◽  
pp. 023
Author(s):  
Svetlana Botsyun ◽  
Pierre Sepulchre ◽  
Camille Risi
Keyword(s):  
Tibetan Plateau ◽  
General Circulation ◽  
Circulation Model ◽  
Mountain Range ◽  
The Tibetan Plateau ◽  
Mountain Ranges ◽  
The Past ◽  
Il Y A ◽  
The Relationship ◽  
Composition Isotopique

Comprendre la dynamique de soulèvement d'une chaîne de montagne nécessite d'en estimer l'altitude passée. C'est le but de la paléoaltimétrie. La méthode la plus répandue utilise la composition isotopique en oxygène des roches carbonatées formées dans les sols et à partir des sédiments lacustres. Celle-ci reflète la composition de la pluie passée qui, dans le monde actuel et dans la plupart des chaînes de montagnes, s'appauvrit progressivement en isotopes lourds avec l'altitude. En supposant que cet appauvrissement reste valide dans le passé, l'altitude du plateau tibétain à l'Éocène (il y a environ 42 millions d'années) est estimée à 4 000 m environ. Mais d'autres marqueurs de l'altitude passée indiquent au contraire des altitudes inférieures à 2 000 m. La relation entre composition isotopique des pluies et altitude observée aujourd'hui s'applique-t-elle à l'Éocène ? C'est ce que nous avons essayé de vérifier en utilisant un modèle de circulation générale atmosphérique, LMDZ-iso. On trouve qu'à l'Éocène la circulation atmosphérique et les processus hydrologiques étaient tellement différents de l'actuel que les observations isotopiques dans les roches carbonatées se trouvent finalement être cohérentes avec des altitudes relativement faibles. Les différentes méthodes de paléo-altimétrie se retrouvent ainsi réconciliées et en accord avec un soulèvement récent (post-Éocène) du plateau tibétain. Understanding the uplift dynamics of a mountain range requires estimating past altitude. This is the purpose of the paleo-altimetry. The most commonly applied paleo-altimetry method is based on the isotopic oxygen composition of the carbonate archives. It reflects the composition of past rain, which at present-day and in the most mountain ranges becomes progressively more depleted in heavy isotopes with altitude. Assuming that this depletion remains valid in the past, the elevation of the Tibetan Plateau in the Eocene (about 42 millions years ago) is estimated to be about 4 000 m. However, other proxy data indicate on the contrary low altitudes. Is the relationship between the rain isotopic composition and the altitude that is observed today applicable to the Eocene? This is what we tried to verify using an atmospheric general circulation model, LMDZ-iso. We find that in the Eocene, the atmospheric circulation and hydrological processes were so different to the present-day that the isotopic observations in the Eocene carbonates are actually consistent with relatively low altitudes of the Plateau. This allows us to reconcile different methods of paleo-altimetry in agreement with more recent (post-Eocene) uplift of the Tibetan Plateau.

scholarly journals Hydrological Impacts of Deforestation on the Southeast Tibetan Plateau

2007 ◽  
Vol 11 (15) ◽  
pp. 1-18 ◽  
Author(s):  
Xuefeng Cui ◽  
Hans-F. Graf ◽  
Baerbel Langmann ◽  
Wen Chen ◽  
Ronghui Huang
Keyword(s):  
Tibetan Plateau ◽  
General Circulation ◽  
Yellow River ◽  
Global Climate ◽  
Statistical Significance ◽  
Circulation Model ◽  
Summer Precipitation ◽  
The Tibetan Plateau ◽  
Ecosystem Research ◽  
Southeast Tibetan Plateau

Abstract The hydrological impact of forest removal on the southeast Tibetan Plateau during the second half of the last century is investigated in this study using an atmospheric general circulation model. The effects of deforestation are investigated by examining the differences between the forest replacement and control experiments. Model results demonstrate that deforestation of the southeast Tibetan Plateau would influence the local and the remote climate as well. It would lead to decreased transpiration and increased summer precipitation in the deforested area and a wetter and warmer climate on the Tibetan Plateau in summer. This may produce more runoff into the rivers originating from the Tibetan Plateau and worsen flooding disasters in the downstream areas. The numerical experiments also show that deforestation would remotely impact Asian climate, and even global climate, although the statistical significance is small. A strong drought is found at middle and lower reaches of the Yellow River, where livelihoods and economics have suffered from recent droughts. Ecosystem research on the Tibetan Plateau is a relatively new topic and needs further interdisciplinary investigation.

scholarly journals Impact of abrupt sea ice loss on Greenland water isotopes during the last glacial period

2019 ◽  
Vol 116 (10) ◽  
pp. 4099-4104 ◽  
Author(s):  
Louise C. Sime ◽  
Peter O. Hopcroft ◽  
Rachael H. Rhodes
Keyword(s):  
Sea Ice ◽  
Temperature Increase ◽  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ice Cores ◽  
Nitrogen Isotope ◽  
Ice Shelf ◽  
Last Glacial Period ◽  
Precipitation Seasonality

Greenland ice cores provide excellent evidence of past abrupt climate changes. However, there is no universally accepted theory of how and why these Dansgaard–Oeschger (DO) events occur. Several mechanisms have been proposed to explain DO events, including sea ice, ice shelf buildup, ice sheets, atmospheric circulation, and meltwater changes. DO event temperature reconstructions depend on the stable water isotope (δ18O) and nitrogen isotope measurements from Greenland ice cores: interpretation of these measurements holds the key to understanding the nature of DO events. Here, we demonstrate the primary importance of sea ice as a control on Greenland ice coreδ18O: 95% of the variability inδ18O in southern Greenland is explained by DO event sea ice changes. Our suite of DO events, simulated using a general circulation model, accurately captures the amplitude ofδ18O enrichment during the abrupt DO event onsets. Simulated geographical variability is broadly consistent with available ice core evidence. We find an hitherto unknown sensitivity of theδ18O paleothermometer to the magnitude of DO event temperature increase: the change inδ18O per Kelvin temperature increase reduces with DO event amplitude. We show that this effect is controlled by precipitation seasonality.

scholarly journals Impact of precipitation intermittency on NAO-temperature signals in proxy records

2013 ◽  
Vol 9 (2) ◽  
pp. 871-886 ◽  
Author(s):  
M. Casado ◽  
P. Ortega ◽  
V. Masson-Delmotte ◽  
C. Risi ◽  
D. Swingedouw ◽  
...  
Keyword(s):  
General Circulation ◽  
Ice Core ◽  
Circulation Model ◽  
Ice Cores ◽  
Stable Isotope Ratio ◽  
Global Network ◽  
Temporal Correlations ◽  
The North ◽  
The North Atlantic Oscillation ◽  
The Impact

Abstract. In mid and high latitudes, the stable isotope ratio in precipitation is driven by changes in temperature, which control atmospheric distillation. This relationship forms the basis for many continental paleoclimatic reconstructions using direct (e.g. ice cores) or indirect (e.g. tree ring cellulose, speleothem calcite) archives of past precipitation. However, the archiving process is inherently biased by intermittency of precipitation. Here, we use two sets of atmospheric reanalyses (NCEP (National Centers for Environmental Prediction) and ERA-interim) to quantify this precipitation intermittency bias, by comparing seasonal (winter and summer) temperatures estimated with and without precipitation weighting. We show that this bias reaches up to 10 °C and has large interannual variability. We then assess the impact of precipitation intermittency on the strength and stability of temporal correlations between seasonal temperatures and the North Atlantic Oscillation (NAO). Precipitation weighting reduces the correlation between winter NAO and temperature in some areas (e.g. Québec, South-East USA, East Greenland, East Siberia, Mediterranean sector) but does not alter the main patterns of correlation. The correlations between NAO, δ18O in precipitation, temperature and precipitation weighted temperature are investigated using outputs of an atmospheric general circulation model enabled with stable isotopes and nudged using reanalyses (LMDZiso (Laboratoire de Météorologie Dynamique Zoom)). In winter, LMDZiso shows similar correlation values between the NAO and both the precipitation weighted temperature and δ18O in precipitation, thus suggesting limited impacts of moisture origin. Correlations of comparable magnitude are obtained for the available observational evidence (GNIP (Global Network of Isotopes in Precipitation) and Greenland ice core data). Our findings support the use of archives of past δ18O for NAO reconstructions.

Modelling high-latitude explosive eruptions and their atmospheric and environmental impacts

2021 ◽  
Author(s):  
Herman Fuglestvedt ◽  
Zhihong Zhuo ◽  
Michael Sigl ◽  
Matthew Toohey ◽  
Michael Mills ◽  
...  
Keyword(s):  
Environmental Impacts ◽  
High Latitude ◽  
Radiative Forcing ◽  
General Circulation ◽  
Lower Thermosphere ◽  
Circulation Model ◽  
Ice Cores ◽  
Volcanic Eruptions ◽  
Explosive Eruptions ◽  
Sulphate Deposition

&lt;p&gt;Large explosive volcanic eruptions inject sulphur into the stratosphere where it is converted to sulphur dioxide and sulphate aerosols. Due to atmospheric circulation patterns, aerosols from high-latitude eruptions typically remain concentrated in the hemisphere in which they are injected. Eruptions in the high-latitude Northern Hemisphere could thus lead to a stronger hemispheric radiative forcing and surface climate response than tropical eruptions, a claim that is supported by a previous study based on proxy records and the coupled aerosol-general circulation model MAECHAM5-HAM. Additionally, the subsequent surface deposition of volcanic sulphate is potentially harmful to humans and ecosystems, and an improved understanding of the deposition over polar ice sheets can contribute to better reconstructions of historical volcanic forcing. On this basis, we model Icelandic explosive eruptions in a pre-industrial atmosphere, taking both volcanic sulphur and halogen loading into account. We use the fully coupled Earth system model CESM2 with the atmospheric component WACCM6, which extends to the lower thermosphere and has prognostic stratospheric aerosols and full chemistry. In order to study the volcanic impacts on the atmosphere, environment, and sulphate deposition, we vary eruption parameters such as sulphur and halogen loading, and injection altitude and season. The modelled volcanic sulphate deposition is compared to the deposition in ice cores following comparable historical eruptions. Furthermore, we evaluate the potential environmental impacts of sulphate deposition. To study inter-model differences, we also compare the CESM2-WACCM6 simulations to similar Icelandic eruption experiments simulated with MAECHAM5-HAM.&amp;#160;&lt;/p&gt;

scholarly journals Climate of Bangladesh: An Analysis of Northwestern and Southwestern Part Using High Resolution Atmosphere-Ocean General Circulation Model (AOGCM)

1970 ◽  
Vol 9 (1-2) ◽  
pp. 143-154 ◽  
Author(s):  
MA Rouf ◽  
MK Uddin ◽  
SK Debsarma ◽  
M Mizanur Rahman
Keyword(s):  
High Resolution ◽  
General Circulation Model ◽  
General Circulation ◽  
Circulation Model ◽  
Ocean General Circulation Model ◽  
Southwestern Part ◽  
The Past ◽  
Average Rainfall ◽  
Ocean General Circulation ◽  
Near Future

The past, present and future climatic pattern (temperature and rainfall) of northwestern and southwestern part of Bangladesh was assessed based on the High Resolution Atmospheric-Ocean General Circulation Model (AOGCM) using the present rainfall and temperature data of the Bangladesh Meteorological Department (BMD). Climatology in Bangladesh is derived from 20 km mesh MRI-AGCM (Atmospheric General Circulation Model) calibrated with reference to the observed data for the period of 1979-2006. Then, projections for rainfall and temperature are made for near future (2015-2034) and future (2075-99). Two disaster prone areas (i) northwestern part (Shapahar & Porsha) and (ii) southwestern part (Kalapara & Amtoli) were selected as the study areas. AOGCM model was run for Bangladesh and also for study areas separately. The present mean temperature for Bangladesh was found to rise from the past, rises slightly, but in near future and future the rate of mean temperature rise is projected to be much more than the present rate (increase up to 4.34 °C/100 years), the rate is projected to be 5.39 °C/100 years in case of Shapahar and Porsha a while 4.37 °C/100 years in case of Kalapara and Amtoli. The present, near future and future average rainfall of Bangladesh appeared to fluctuate, but have shown a decreasing trend (decreases up to 1.96 mm/100 years). The mean average rainfall of Shapahar and Porsha presently decreases very slowly (not significant), but in near future and future will decrease slowly (0.66mm/100 years). In case of Kalapara, the average rainfall appears to decrease presently, near future and future will decrease up to 3.62 mm/100 years. The average rainfall of Amtoli appears to decrease @ 1.92mm/100 years but in near future appears to increase slightly and again decrease @ 3.27mm/100years in future. Keywords: Atmosphere-Ocean General Circulation Model (AOGCM); climatology; simulation; temperature; rainfall DOI: http://dx.doi.org/10.3329/agric.v9i1-2.9489 The Agriculturists 2011; 9(1&2): 143-154

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