Increasing aridity over the past 223 years in the Nepal Himalaya inferred from a tree-ring δ18O chronology

The Holocene ◽  
2011 ◽  
Vol 22 (7) ◽  
pp. 809-817 ◽  
Author(s):  
Masaki Sano ◽  
R Ramesh ◽  
MS Sheshshayee ◽  
R Sukumar
Keyword(s):  
Tree Ring ◽  
Summer Monsoon ◽  
Function Analysis ◽  
Monsoon Season ◽  
Sea Surface ◽  
Drought Severity ◽  
Sea Surface Temperatures ◽  
Nepal Himalaya ◽  
The Past ◽  
Surface Temperatures

A tree-ring δ18O chronology of Abies spectabilis from the Nepal Himalaya was established to study hydroclimate in the summer monsoon season over the past 223 years (ad 1778–2000). Response function analysis with ambient climatic records revealed that tree-ring δ18O was primarily controlled by the amount of precipitation and relative humidity during the monsoon season (June–September). Since tree-ring δ18O was simultaneously correlated with temperature, drought history in the monsoon season was reconstructed by calibrating against the Palmer Drought Severity Index (PDSI). Our reconstruction that accounts for 33.7% of the PDSI variance shows a decreasing trend of precipitation/moisture over the past two centuries, and reduction of monsoon activity can be found across different proxy records from the Himalaya and Tibet. Spatial correlation analysis with global sea surface temperatures suggests that the tropical oceans play a role in modulating hydroclimate in the Nepal Himalaya. Although the dynamic mechanisms of the weakening trend of monsoon intensity still remain to be analyzed, rising sea surface temperatures over the tropical Pacific and Indian Ocean could be responsible for the reduction of summer monsoon.

scholarly journals Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

2008 ◽  
Vol 4 (2) ◽  
pp. 107-124 ◽  
Author(s):  
L. M. Dupont ◽  
H. Behling ◽  
J.-H. Kim
Keyword(s):  
Rain Forest ◽  
Vegetation History ◽  
First Record ◽  
Dry Forest ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Miombo Woodlands ◽  
Vegetation Development ◽  
The Past ◽  
Surface Temperatures

Abstract. ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1, a northward excursion of the Angola Benguela Front and the Congo Air Boundary resulted in cool sea surface temperatures but rain forest remained present in the northern lowlands of Angola. Rain forest and dry forest area increase 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.

scholarly journals Thirty thousand years of vegetation development and climate change in Angola (Ocean Drilling Program Site 1078)

2008 ◽  
Vol 4 (1) ◽  
pp. 111-147 ◽  
Author(s):  
L. M. Dupont ◽  
H. Behling ◽  
J.-H. Kim
Keyword(s):  
Vegetation History ◽  
First Record ◽  
Dry Forest ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Miombo Woodlands ◽  
Ocean Drilling Program ◽  
Vegetation Development ◽  
The Past ◽  
Surface Temperatures

Abstract. ODP Site 1078 situated under the coast of Angola provides the first record of the vegetation history for Angola. The upper 11 m of the core covers the past 30 thousand years, which has been analysed palynologically in decadal to centennial resolution. Alkenone sea surface temperature estimates were analysed in centennial resolution. We studied sea surface temperatures and vegetation development during full glacial, deglacial, and interglacial conditions. During the glacial the vegetation in Angola was very open consisting of grass and heath lands, deserts and semi-deserts, which suggests a cool and dry climate. A change to warmer and more humid conditions is indicated by forest expansion starting in step with the earliest temperature rise in Antarctica, 22 thousand years ago. We infer that around the period of Heinrich Event 1 a northward excursion of the Angola Benguela Front and the Congolian Air Boundary resulted in cool sea surface temperatures and a northward extension of desert vegetation along the coast. Rain forest and dry forest returned 15 thousand years ago. During the Holocene, dry forests and Miombo woodlands expanded. Also in Angola globally recognised climate changes at 8 thousand and 4 thousand years ago had an impact on the vegetation. During the past 2 thousand years, savannah vegetation became dominant.

scholarly journals Spatiotemporal Decompositions of Summer Drought in China and Its Teleconnection with Global Sea Surface Temperatures during 1901–2012

2017 ◽  
Vol 30 (16) ◽  
pp. 6391-6412 ◽  
Author(s):  
Yaxin Zhang ◽  
Mengxi Wu ◽  
Delong Li ◽  
Yonggang Liu ◽  
Shuangcheng Li
Keyword(s):  
Tibetan Plateau ◽  
Eastern China ◽  
Northern China ◽  
Sea Surface ◽  
Drought Severity ◽  
Summer Drought ◽  
The Tibetan Plateau ◽  
Sea Surface Temperatures ◽  
Spatial And Temporal Scales ◽  
Surface Temperatures

The teleconnection between the summer (June–August) Palmer drought severity index (PDSI) in China and seasonal global sea surface temperatures (SSTs) is investigated at both spatial and temporal scales during 1901–2012. Three pairs of coupled spatial patterns for China’s PDSI and global SST anomalies are identified using the singular value decomposition (SVD) method. With a combination of ensemble empirical mode decomposition (EEMD) and multiple linear regression (MLR) analysis, it is found that the first mode, the sea ice loss–global warming pattern, causes wetness over north and northeastern China and drying over Inner Mongolia. The North Pacific Current (NPC) mode shows that a warmer NPC corresponds to a wetter summer over eastern China and a drier one over the Tibetan Plateau. Both NPC and Pacific decadal oscillation (PDO) affect moisture variability in northern China and over the Tibetan Plateau, with the NPC mode more important in the centennial scale, while the PDO mode is more important in the multidecadal scale.

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