scholarly journals Late Pleistocene Paleoceanographic Changes of the West Equatorial Pacific

2004 ◽  
Vol 26 (2) ◽  
pp. 175-185
Author(s):  
Chan-Min Yoo ◽  
Ki-Seong Hyeong ◽  
Jai-Woon Moon ◽  
Ki-Hyune Kim ◽  
Sang-Bum Chi
Keyword(s):  
Late Pleistocene ◽  
Equatorial Pacific ◽  
The West

Climatic implications of latest Pleistocene and earliest Holocene mammalian sympatries in eastern Washington state, USA

2008 ◽  
Vol 70 (3) ◽  
pp. 426-432 ◽  
Author(s):  
R. Lee Lyman
Keyword(s):  
North America ◽  
Late Pleistocene ◽  
Rocky Mountains ◽  
Taxonomic Composition ◽  
Washington State ◽  
The West ◽  
Mammalian Faunas ◽  
Eastern Washington

AbstractFor more than fifty years it has been known that mammalian faunas of late-Pleistocene age are taxonomically unique and lack modern analogs. It has long been thought that nonanalog mammalian faunas are limited in North America to areas east of the Rocky Mountains and that late-Pleistocene mammalian faunas in the west were modern in taxonomic composition. A late-Pleistocene fauna from Marmes Rockshelter in southeastern Washington State has no modern analog and defines an area of maximum sympatry that indicates significantly cooler summers than are found in the area today. An earliest Holocene fauna from Marmes Rockshelter defines an area of maximum sympatry, including the site area, but contains a single tentatively identified taxon that may indicate slightly cooler than modern summers.

scholarly journals La Niña–like Mean-State Response to Global Warming and Potential Oceanic Roles

2017 ◽  
Vol 30 (11) ◽  
pp. 4207-4225 ◽  
Author(s):  
Tsubasa Kohyama ◽  
Dennis L. Hartmann ◽  
David S. Battisti
Keyword(s):  
Global Warming ◽  
Southern Oscillation ◽  
Forced Response ◽  
Equatorial Pacific ◽  
La Niña ◽  
The West ◽  
La Nina ◽  
The Mean ◽  
Mean State ◽  
Sst Gradient

Abstract The majority of the models that participated in phase 5 of the Coupled Model Intercomparison Project global warming experiments warm faster in the eastern equatorial Pacific Ocean than in the west. GFDL-ESM2M is an exception among the state-of-the-art global climate models in that the equatorial Pacific sea surface temperature (SST) in the west warms faster than in the east, and the Walker circulation strengthens in response to warming. This study shows that this “La Niña–like” trend simulated by GFDL-ESM2M could be a physically consistent response to warming, and that the forced response could have been detectable since the late twentieth century. Two additional models are examined: GFDL-ESM2G, which differs from GFDL-ESM2M only in the oceanic components, warms without a clear zonal SST gradient; and HadGEM2-CC exhibits a warming pattern that resembles the multimodel mean. A fundamental observed constraint between the amplitude of El Niño–Southern Oscillation (ENSO) and the mean-state zonal SST gradient is reproduced well by GFDL-ESM2M but not by the other two models, which display substantially weaker ENSO nonlinearity than is observed. Under this constraint, the weakening nonlinear ENSO amplitude in GFDL-ESM2M rectifies the mean state to be La Niña–like. GFDL-ESM2M exhibits more realistic equatorial thermal stratification than GFDL-ESM2G, which appears to be the most important difference for the ENSO nonlinearity. On longer time scales, the weaker polar amplification in GFDL-ESM2M may also explain the origin of the colder equatorial upwelling water, which could in turn weaken the ENSO amplitude.

Fluctuations in Terrestrial–Marine Environments in the Western Equatorial Pacific during the Late Pleistocene

2002 ◽  
Vol 57 (1) ◽  
pp. 71-81 ◽  
Author(s):  
Hodaka Kawahata ◽  
Rena Maeda ◽  
Hideaki Ohshima
Keyword(s):  
Late Pleistocene ◽  
Accumulation Rate ◽  
Global Climate ◽  
New Guinea ◽  
Equatorial Pacific ◽  
Pollen Record ◽  
Western Equatorial Pacific ◽  
Large Heat ◽  
Pollen And Spores ◽  
Marine Environmental

AbstractLarge heat storage capacity in the western equatorial Pacific has played an important role in modulating global climate. The fluctuation in pollen and spore abundances, together with organic matter (OM) and lithogenics sedimentation, was investigated to reconstruct terrestrial and marine environmental change around New Guinea during the Late Pleistocene. Although appreciable contribution from Indonesian Maritime Continent was expected, the majority of the pollen and spore grains found in core C4402 was transported from New Guinea. Fern spores accounted for 70% (46–90%) of the total pollens and spores. Positive correlation between lithogenic content and the relative abundance of fern spores suggests that lithogenics could be derived from coastal lowland.The mass accumulation rate (MAR) of pollen and spores varied from 44 to 7,031×10−3 grains cm−2 yr−1 with maxima in oxygen isotope stages (OIS) 2, 3, 4, and around the OIS 4/5 boundary. Less rainfall during glacial times generally enhanced transport of pollen by wind to Site C4402. Their scavenging from the water column was promoted by high activity of the biological pump. Pollen record from core C4402 suggests that lower montane group vegetation was dominant relative to lowland vegetation and upper and mid-montane group during glacial times. Although appreciable contribution by terrestrial OM is expected from high correlation of MAR between organic carbon (OC) and pollen and spores, fairly low COrganic/N ratios and δ13C values (around −20‰) of OM demonstrate that OM in core C4402 is mainly of marine origin.

Late Pleistocene vertebrates from downtown San Francisco, California

1993 ◽  
Vol 67 (6) ◽  
pp. 1058-1063 ◽  
Author(s):  
Peter U. Rodda ◽  
Nina Baghai
Keyword(s):  
San Francisco ◽  
Late Pleistocene ◽  
San Francisco Bay ◽  
The West ◽  
Terrestrial Vertebrates ◽  
Sandy Clay ◽  
Geologic Setting ◽  
The City

Disarticulated elements from three individuals of Mammuthus cf. M. columbi (Falconer) and one individual of Bison cf. B. latifrons (Harlan) were recovered from an excavation in gravelly, sandy clay of the Colma Formation at the southeast base of Telegraph Hill, San Francisco, California. This is the most abundant collection of late Pleistocene terrestrial vertebrates reported from San Francisco, and only the fourth record from excavations in the city proper. The Mammuthus-Bison association indicates a Rancholabrean age, and elements of these two taxa from this site have been radiocarbon dated at 25,380 ± 1,100 years B.P. Geologic setting, lithology, associated diatoms and pollen, and preservation of the bones suggest that these animals were buried rapidly in a boggy environment on the west margin of the broad valley now occupied by San Francisco Bay.

scholarly journals Late Pleistocene Tephrostratigraphy of the Eastern Bay of Plenty Region, New Zealand

2021 ◽  
Author(s):  
◽  
David Alaric Manning
Keyword(s):  
New Zealand ◽  
Late Pleistocene ◽  
Large Scale ◽  
Late Quaternary ◽  
Volcanic Centre ◽  
The West ◽  
Uplift Rates ◽  
Climate Indicator ◽  
Far Eastern ◽  
Block Faulting

<p>This thesis has produced the compilation of a complete tephrostratigraphic record of the eastern Bay of Plenty, New Zealand. About fifty Late Pleistocene tephras (i.e. those older than the Rotoiti eruption), ranging in age from c. 600 to 50 ka, are recorded in a terrestrial sequence of loess and paleosols in the eastern Bay of Plenty. Tephra correlations are based on the distinctive physical characteristics of the airfall beds and confirmed by microprobe analysis of glass shards ("fingerprinting"). Chemical analysis of hornblendes and titanomagnetites is used as a supplementary correlation tool where the tephras are too weathered to retain glass. The eastern bay of Plenty deposits are divided into seven subgroups with their boundaries marked either by major tephras or by significant changes in the paleo-climate indicator deposits such as loess and paleosols. These subgroups, and their estimated age ranges, are: Age control on the eastern Bay of Plenty tephras has been obtained by fitting the paleoclimatic information inferred from field observations to the Low Latitude Stack (LLS) and SPECMAP oxygen isotope curves, with correlations to a few well dated eruptives providing key time planes within this record; in particular, the Mamaku Ignimbrite (correlates to the Kutarere Tephra), and the Kaingaroa (Kaingaroa), Matahina (Matahina) and Rangitaiki (Kohioawa) Ignimbrites. Tentative correlations of several eastern Bay of Plenty tephras to the western, coastal central, and Southeast-central Bay of Plenty areas (Tauranga Matata cliffs and Reporoa, respectively) have been achieved. Three additional subgroups are proposed: the Welcome Bay (with at least 6 tephras) in the west, the Ohinekoao (14 tephras) in the coastal central, and the Reihana (13 tephras) in the southeast-central Bay of Plenty; all of which overlap in time with the eastern Bay of Plenty stratigraphy. The tephras recorded in the Bay of plenty have been used to estimate the ages of formation and uplift rates for many of the landforms that are observed throughout the region. A tectonic regime of subsidence in the west towards Tauranga, block faulting on either side of the subsiding Whakatane Graben in the central Bay of Plenty, and further large scale block faulting towards the far eastern margin of the Bay of Plenty has been proposed. Activity at the Okataina Volcanic Centre is now thought to have initiated at or before c. 370 ka, with the eruption of the Paerata Tephra. This tephra has a distribution pattern consistent with an Okataina source, and contains abundant cummingtonite, which is a signature mineral within tephras from the Okataina Volcanic Centre during the late Quaternary time period. However, the much older, but less well understood, Reeves-A and Wilson Tephras - both with estimated ages of c. 0.5 Ma - also contain cummingtonite, which indicates that activity may have been initiation at a much earlier time, or that a volcanic centre other than Okataina has produced cummingtonite. Activity in the Rotorua Volcanic Centre prior to the eruption of the Mamaku Ignimbrite is also indicated, as is activity at the Reporoa Volcanic Centre prior to the Kaingaroa Ignimbrite eruption.</p>

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