Holocene hydroclimatic variability in the Zanskar Valley, Northwestern Himalaya, India

2020 ◽  
Vol 97 ◽  
pp. 140-156 ◽  
Author(s):  
Sheikh Nawaz Ali ◽  
Shailesh Agrawal ◽  
Anupam Sharma ◽  
Binita Phartiyal ◽  
Paulramasamy Morthekai ◽  
...  
Keyword(s):  
Western Himalaya ◽  
High Amplitude ◽  
Progressive Increase ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Nw Himalaya ◽  
Centennial Time Scale ◽  
Hydroclimatic Variability ◽  
Short Time ◽  
Grain Size Parameters

AbstractA 1.3-m-long sediment core from the Penzi-la pass, Zanskar Valley, provides a record of hydroclimatic conditions and abrupt climate changes over short time scales since the mid-Holocene. These climatic changes of centennial time scale are crucial to understanding the hydroclimatic variability in northwestern (NW) Himalaya. Relatively higher δ13C values complemented by total organic carbon, loss on ignition, grain size parameters, and lower Rubidium/Strontium ratios during the Late Northgrippian imply that the area had a dry climate during the period from ~6200–4500 cal yr BP. Subsequently, a relatively stable hydroclimatic environment was experienced between ~4500 and 3400 cal yr BP. After ~3400 cal yr BP the multiproxy data show gradual strengthening of hydroclimatic conditions, however, this trend is interrupted by high-amplitude abrupt reversals (dry events) with a stepwise decreasing intensity at ~3300, 2600, 1700, and 400 cal yr BP. The two most important climatic events of the last millennia (i.e., Medieval Climate Anomaly and the Little Ice Age) were also recorded from the sedimentary archive. Overall, our data show a progressive increase in the moisture availability in the Zanskar Valley and are in agreement with the late Holocene climatic trends of central and western Himalaya.

Characterization of the Medieval Climate Anomaly, Little Ice Age and recent warming in northern Lapland

2017 ◽  
Vol 37 ◽  
pp. 1257-1266 ◽  
Author(s):  
Tomi P. Luoto ◽  
E. Henriikka Kivilä ◽  
Marttiina V. Rantala ◽  
Liisa Nevalainen
Keyword(s):  
Little Ice Age ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Recent Warming

scholarly journals Interhemispheric gradient of atmospheric radiocarbon reveals natural variability of Southern Ocean winds

2011 ◽  
Vol 7 (1) ◽  
pp. 347-379 ◽  
Author(s):  
K. B. Rodgers ◽  
S. E. M. Fletcher ◽  
D. Bianchi ◽  
C. Beaulieu ◽  
E. D. Galbraith ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Little Ice Age ◽  
Driving Forces ◽  
Ice Age ◽  
Global Maximum ◽  
Medieval Climate Anomaly ◽  
Ocean Winds ◽  
Main Driver ◽  
14Co2 Production ◽  
Ocean Wind

Abstract. Tree ring Δ14C data (Reimer et al., 2004; McCormac et al., 2004) indicate that atmospheric Δ14C varied on multi-decadal to centennial timescales, in both hemispheres, over the pre-industrial period AD 950–1830. Although the Northern and Southern Hemispheric Δ14C records display similar variability, it is difficult from these data alone to distinguish between variations driven by 14CO2 production in the upper atmosphere (Stuiver, 1980) and exchanges between carbon reservoirs (Siegenthaler, 1980). Here we consider rather the Interhemispheric Gradient in atmospheric Δ14C as revealing of the background pre-bomb air-sea Disequilbrium Flux between 14CO2 and CO2. As the global maximum of the Disequilibrium Flux is squarely centered in the open ocean regions of the Southern Ocean, relatively modest perturbations to the winds over this region drive significant perturbations to the Interhemispheric Gradient. The analysis presented here implies that changes to Southern Ocean windspeeds are likely a main driver of the observed variability in the Interhemispheric Gradient over 950–1830, and further, that this variability may be larger than the Southern Ocean wind trends that have been reported for recent decades (notably 1980–2004). This interpretation also implies a significant weakening of the winds over the Southern Ocean within a few decades of AD 1375, associated with the transition between the Medieval Climate Anomaly and the Little Ice Age. The driving forces that could have produced such a shift in the winds remain unkown.

The residence time of Southern Ocean surface waters and the 100,000-year ice age cycle

Science ◽  
2019 ◽  
Vol 363 (6431) ◽  
pp. 1080-1084 ◽  
Author(s):  
Adam P. Hasenfratz ◽  
Samuel L. Jaccard ◽  
Alfredo Martínez-García ◽  
Daniel M. Sigman ◽  
David A. Hodell ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Residence Time ◽  
Surface Waters ◽  
High Amplitude ◽  
Ice Age ◽  
Ice Ages ◽  
Glacial Cycle ◽  
Surface Circulation ◽  
Carbon Dioxide Release ◽  
The Antarctic

From 1.25 million to 700,000 years ago, the ice age cycle deepened and lengthened from 41,000- to 100,000-year periodicity, a transition that remains unexplained. Using surface- and bottom-dwelling foraminifera from the Antarctic Zone of the Southern Ocean to reconstruct the deep-to-surface supply of water during the ice ages of the past 1.5 million years, we found that a reduction in deep water supply and a concomitant freshening of the surface ocean coincided with the emergence of the high-amplitude 100,000-year glacial cycle. We propose that this slowing of deep-to-surface circulation (i.e., a longer residence time for Antarctic surface waters) prolonged ice ages by allowing the Antarctic halocline to strengthen, which increased the resistance of the Antarctic upper water column to orbitally paced drivers of carbon dioxide release.

Lacustrine stable isotope record of precipitation changes in Nicaragua during the Little Ice Age and Medieval Climate Anomaly

Geology ◽  
2013 ◽  
Vol 41 (2) ◽  
pp. 151-154 ◽  
Author(s):  
Nathan D. Stansell ◽  
Byron A. Steinman ◽  
Mark B. Abbott ◽  
Michael Rubinov ◽  
Manuel Roman-Lacayo
Keyword(s):  
Stable Isotope ◽  
Little Ice Age ◽  
Ice Age ◽  
Medieval Climate Anomaly ◽  
Climate Anomaly ◽  
Isotope Record ◽  
Precipitation Changes ◽  
Stable Isotope Record

scholarly journals South Atlantic Surface Boundary Current System during the Last Millennium in the CESM-LME: The Medieval Climate Anomaly and Little Ice Age

Geosciences ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 299
Author(s):  
Fernanda Marcello ◽  
Ilana Wainer ◽  
Peter R. Gent ◽  
Bette L. Otto-Bliesner ◽  
Esther C. Brady
Keyword(s):  
Little Ice Age ◽  
South Atlantic ◽  
Subtropical Gyre ◽  
Ice Age ◽  
Surface Boundary ◽  
South American ◽  
Last Millennium ◽  
Medieval Climate Anomaly ◽  
The South ◽  
Gyre Circulation

Interocean waters that are carried northward through South Atlantic surface boundary currents get meridionally split between two large-scale systems when meeting the South American coast at the western subtropical portion of the basin. This distribution of the zonal flow along the coast is investigated during the Last Millennium, when natural forcing was key to establish climate variability. Of particular interest are the changes between the contrasting periods of the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). The investigation is conducted with the simulation results from the Community Earth System Model Last Millennium Ensemble (CESM-LME). It is found that the subtropical South Atlantic circulation pattern differs substantially between these natural climatic extremes, especially at the northern boundary of the subtropical gyre, where the westward-flowing southern branch of the South Equatorial Current (sSEC) bifurcates off the South American coast, originating the equatorward-flowing North Brazil Undercurrent (NBUC) and the poleward Brazil Current (BC). It is shown that during the MCA, a weaker anti-cyclonic subtropical gyre circulation took place (inferred from decreased southern sSEC and BC transports), while the equatorward transport of the Meridional Overturning Circulation return flow was increased (intensified northern sSEC and NBUC). The opposite scenario occurs during the LIA: a more vigorous subtropical gyre circulation with decreased northward transport.

scholarly journals Analysis of Large-Amplitude Pulses in Short Time Intervals: Application to Neuron Interactions

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Gianni Mattioli ◽  
Massimo Scalia ◽  
Carlo Cattani
Keyword(s):  
Dynamical System ◽  
Order Approximation ◽  
Nonlinear Dynamical System ◽  
High Amplitude ◽  
Time Dependent ◽  
Third Order ◽  
Time Intervals ◽  
Nonlinear Dynamical ◽  
Short Time ◽  
Third Order Approximation

This paper deals with the analysis of a nonlinear dynamical system which characterizes the axons interaction and is based on a generalization of FitzHugh-Nagumo system. The parametric domain of stability is investigated for both the linear and third-order approximation. A further generalization is studied in presence of high-amplitude (time-dependent) pulse. The corresponding numerical solution for some given values of parameters are analyzed through the wavelet coefficients, showing both the sensitivity to local jumps and some unexpected inertia of neuron's as response to the high-amplitude spike.

Vegetation shifts, human impact and peat bog development in Bassa Nera pond (Central Pyrenees) during the last millennium

The Holocene ◽  
2016 ◽  
Vol 27 (4) ◽  
pp. 553-565 ◽  
Author(s):  
Sandra Garcés-Pastor ◽  
Núria Cañellas-Boltà ◽  
Albert Clavaguera ◽  
Miguel Angel Calero ◽  
Teresa Vegas-Vilarrúbia
Keyword(s):  
Environmental Changes ◽  
Ice Age ◽  
Peat Bog ◽  
High Mountain ◽  
Last Millennium ◽  
Medieval Climate Anomaly ◽  
Human Pressure ◽  
Climate Anomaly ◽  
Vegetation Shifts ◽  
Central Pyrenees

High-mountain lakes are suitable ecosystems for studying local environmental shifts driven by large-scale climate changes, with potential applications to predict future scenarios. The precise features in the response of species assemblages are not fully understood, and human pressure may often hide climatic signals. To investigate the origin and impact of past environmental changes in high-mountain ecosystems and apply this palaeoecological knowledge to anticipate future changes, we performed a multi-proxy study of a sediment core from Bassa Nera, a pond located close to montane–subalpine ecotone in the southern central Pyrenees. Combining pollen and diatom analysis at multidecadal resolution, we inferred vegetation shifts and peat bog development during the past millennium. We introduced a montane pollen ratio as a new palaeoecological indicator of altitudinal shifts in vegetation. Our results emphasize the sensitivity of the montane ratio to detect upward migrations of deciduous forest and the presence of the montane belt close to Bassa Nera pond during the Medieval Climate Anomaly. Changes in aquatic taxa allowed to date the onset of the surrounding peat bog which appeared and infilled the coring site around AD 1565. Overall, our results suggest a low-intensity human pressure and changes in management of natural resources during the last millennium, where farming was the main activity from the Medieval Climate Anomaly until AD 1500. Afterwards, people turned to highland livestock raising coinciding with the ‘Little Ice Age’.

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