scholarly journals A Geophysical and Climatological Assessment of New Guinea — Implications for the Origins of Saccharum

2020 ◽  
Author(s):  
Dyfed Lloyd Evans
Keyword(s):  
Global Climate ◽  
New Guinea ◽  
North Coast ◽  
Tsunami Modelling ◽  
The North ◽  
The Pacific ◽  
Human Colonization ◽  
The Last Glacial Maximum ◽  
Modern Form ◽  
The Last Glacial

AbstractAny assessment of whether or not Saccharum species are native or introduced in New Guinea require an evolutionary (in a geological sense), geophysical and climatological assessment of the island. Like many of the land masses circling the Pacific (in the volcanically active region known as the ‘ring of fire’) New Guinea is geologically young, with the island in its modern form not pre-dating 2 Ma. Novel modelling of the 74 ka youngest Toba supereruption indicates a potential extinction level tsunami and loss of habitat. The late Pleistocene megafaunal mass extinction and the last glacial maximum (33–16 ka) are two global effects that would have significantly altered the flora on New Guinea; though the implications of these events on New Guinea have not previously been studied. Even if the genus Saccharum was established on the island during pre-historic times the consequences of Toba and other global climate change events means that it would have been eliminated from New Guinea and would have had to be re-introduced during the period of human colonization. Indeed, given the evolution of Saccharum’s immediate ancestors in Africa and Indochina it is most parsimonious to conclude that it was never native to New Guinea, but was introduced by humans relatively recently.Little work has been done on palaeotsunami evidence and ancient tsunami modelling in New Guinea. However, the recent recognition that the Aitape skull (dating to about 6 ka) may have been the victim of a tsunami (Goff et al. 2017) show that, in the past, tsunami have pen etrated significantly (about 10 km in this case) into the interior of the island to have a profound effect on biodiversity. This tsunami would have left the north coast of the island impoverished of plant life for several decades after.

scholarly journals Initial peopling of North America: paleogeography and archaeology

2019 ◽  
pp. 131-140
Author(s):  
S. A. Vasilyev
Keyword(s):  
North America ◽  
Land Bridge ◽  
Southeastern Part ◽  
Single Wave ◽  
The North ◽  
Human Movements ◽  
The Pacific ◽  
The Usa ◽  
The Last Glacial Maximum ◽  
The Last Glacial

The paper contains a summary of the new data relevant to the time and routes of the first peopling of the New World. The first unambiguous traces of humans are dated by the time span after the Last Glacial Maximum. The chronology and orientation of prehistoric migrations depended on the Late Pleistocene paleogeography. Instead of a postulated single wave of migration oriented from NW to SE from the Bering Land Bridge via the Mackenzie ice-free corridor to the territory lying southwards from the ice sheets we argue about a complicated picture of human movements of different age and direction. It seems that the earliest inhabitants penetrated from Beringia to the main area of North America following the Pacific coast and later dispersed to the east. The migration along the Mackenzie ice-free corridor should have place later. The Clovis culture seems to originate in the southeastern part of the USA territory then dispersing in northern and western directions along the whole continent. The Final Pleistocene saw the ‘inverse’ migration of the Paleoindians to the north, along the Mackenzie corridor to Beringia.

scholarly journals A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic δ<sup>13</sup>C gradient

2009 ◽  
Vol 5 (6) ◽  
pp. 2607-2630 ◽  
Author(s):  
L. E. Lisiecki
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
North Pacific ◽  
Deep Ocean ◽  
South Atlantic ◽  
The North ◽  
The Pacific ◽  
The Last Glacial Maximum ◽  
The North Pacific ◽  
The Last Glacial

Abstract. The fact that the deep-ocean benthic δ13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific. This study re-evaluates the implications of changes in benthic δ13C gradients by comparing Pacific Deep Water (PDW) δ13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The δ13C compositions of PDW, Northern Component Water (NCW) and Southern Component Water (SCW) are estimated from regional benthic δ13C stacks of 3–6 sites. Changes in PDW δ13C and PDW-SCW δ13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific "age" offset of −0.5‰. Thus, an additional ventilation source for glacial PDW (e.g., in the North Pacific) cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic δ13C gradient.

scholarly journals A simple mixing explanation for late Pleistocene changes in the Pacific-South Atlantic benthic δ<sup>13</sup>C gradient

2010 ◽  
Vol 6 (3) ◽  
pp. 305-314 ◽  
Author(s):  
L. E. Lisiecki
Keyword(s):  
Late Pleistocene ◽  
Deep Water ◽  
North Pacific ◽  
Deep Ocean ◽  
South Atlantic ◽  
The North ◽  
The Pacific ◽  
The Last Glacial Maximum ◽  
The North Pacific ◽  
The Last Glacial

Abstract. The fact that the deep-ocean benthic δ13C minimum shifted from the North Pacific to the South Atlantic during the Last Glacial Maximum is often interpretted as evidence of a change in deep water circulation, such as the development of deep water ventilation in the North Pacific or a decrease in Southern Ocean overturning. This study re-evaluates the implications of changes in benthic δ13C gradients by comparing Pacific Deep Water (PDW) δ13C measurements with the values expected for the null hypothesis that PDW ventilation sources remained unchanged throughout the Late Pleistocene. The δ13C compositions of PDW, Northern Component Water (NCW) and Southern Component Water (SCW) are estimated from regional benthic δ13C stacks of 3–6 sites. Changes in PDW δ13C and PDW-SCW δ13C gradients over the past 800 kyr are found to be well described by a constant mixture of 60% NCW and 40% SCW plus a constant Pacific remineralization offset of −0.5‰. Thus, a change in PDW ventilation cannot be inferred solely on the basis of changes in the Pacific-South Atlantic benthic δ13C gradient.

scholarly journals The evolving response of mesopelagic fishes to declining midwater oxygen concentrations in the southern and central California Current

2018 ◽  
Vol 76 (3) ◽  
pp. 626-638 ◽  
Author(s):  
J Anthony Koslow ◽  
Pete Davison ◽  
Erica Ferrer ◽  
S Patricia A Jiménez Rosenberg ◽  
Gerardo Aceves-Medina ◽  
...  
Keyword(s):  
Baja California ◽  
Southern Oscillation ◽  
Global Climate ◽  
California Current ◽  
Deep Ocean ◽  
Near Surface ◽  
Oxygen Minimum Zones ◽  
The North ◽  
The Pacific ◽  
Oxygen Concentrations

Abstract Declining oxygen concentrations in the deep ocean, particularly in areas with pronounced oxygen minimum zones (OMZs), are a growing global concern related to global climate change. Its potential impacts on marine life remain poorly understood. A previous study suggested that the abundance of a diverse suite of mesopelagic fishes off southern California was closely linked to trends in midwater oxygen concentration. This study expands the spatial and temporal scale of that analysis to examine how mesopelagic fishes are responding to declining oxygen levels in the California Current (CC) off central, southern, and Baja California. Several warm-water mesopelagic species, apparently adapted to the shallower, more intense OMZ off Baja California, are shown to be increasing despite declining midwater oxygen concentrations and becoming increasingly dominant, initially off Baja California and subsequently in the CC region to the north. Their increased abundance is associated with warming near-surface ocean temperature, the warm phase of the Pacific Decadal oscillation and Multivariate El Niño-Southern Oscillation Index, and the increased flux of Pacific Equatorial Water into the southern CC.

scholarly journals Reconstruction of North American drainage basins and river discharge since the Last Glacial Maximum

2016 ◽  
Vol 4 (4) ◽  
pp. 831-869 ◽  
Author(s):  
Andrew D. Wickert
Keyword(s):  
North American ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Glacial Isostatic Adjustment ◽  
Drainage Basins ◽  
Last Glacial ◽  
Isostatic Adjustment ◽  
The North ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. Over the last glacial cycle, ice sheets and the resultant glacial isostatic adjustment (GIA) rearranged river systems. As these riverine threads that tied the ice sheets to the sea were stretched, severed, and restructured, they also shrank and swelled with the pulse of meltwater inputs and time-varying drainage basin areas, and sometimes delivered enough meltwater to the oceans in the right places to influence global climate. Here I present a general method to compute past river flow paths, drainage basin geometries, and river discharges, by combining models of past ice sheets, glacial isostatic adjustment, and climate. The result is a time series of synthetic paleohydrographs and drainage basin maps from the Last Glacial Maximum to present for nine major drainage basins – the Mississippi, Rio Grande, Colorado, Columbia, Mackenzie, Hudson Bay, Saint Lawrence, Hudson, and Susquehanna/Chesapeake Bay. These are based on five published reconstructions of the North American ice sheets. I compare these maps with drainage reconstructions and discharge histories based on a review of observational evidence, including river deposits and terraces, isotopic records, mineral provenance markers, glacial moraine histories, and evidence of ice stream and tunnel valley flow directions. The sharp boundaries of the reconstructed past drainage basins complement the flexurally smoothed GIA signal that is more often used to validate ice-sheet reconstructions, and provide a complementary framework to reduce nonuniqueness in model reconstructions of the North American ice-sheet complex.

scholarly journals A Climatological Interpretation of the Circulation in the Western South Pacific*

2002 ◽  
Vol 32 (9) ◽  
pp. 2492-2508 ◽  
Author(s):  
Tangdong Qu ◽  
Eric J. Lindstrom
Keyword(s):  
Papua New Guinea ◽  
New Guinea ◽  
Western Boundary ◽  
Guinea Coast ◽  
Boundary Currents ◽  
The North ◽  
Intermediate Layers ◽  
Water Property ◽  
The Pacific ◽  
Equatorial Current

Abstract Time-averaged circulation is examined using historical hydrographic data near the Australia and Papua New Guinea coast in the Pacific. By averaging the data along isopycnal surfaces in a 0.5° × 0.5° grid, the authors are able to show many detailed phenomena associated with the narrow western boundary currents, including the vertical structure of the bifurcation latitude of the South Equatorial Current (SEC) and the connection between the Solomon and Coral Seas. The bifurcation latitude of the SEC is found to move southward from about 15°S near the surface to south of 22°S in the intermediate layers. The origin of the Great Barrier Reef Undercurrent (GBRUC) is identified to be at about 22°S. Farther to the north, the GBRUC intensifies underlying the surface East Australian Current, and merges with the North Queensland Current (NQC) at about 15°S. The NQC turns eastward to flow along the Papua New Guinea coast and feeds into the New Guinea Coastal Undercurrent (NGCUC) through the Louisiade Archipelago. Further analysis shows that there is a strong water property connection between the Coral and Solomon Seas, confirming the earlier speculation on the water mass origins of the NGCUC.

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