Climatic, Solar, Oceanic, and Geomagnetic Influences on Late-Glacial and Holocene Atmospheric 14C/12C Change

1991 ◽  
Vol 35 (1) ◽  
pp. 1-24 ◽  
Author(s):  
Minze Stuiver ◽  
Thomas F. Braziunas ◽  
Bernd Becker ◽  
Bernd Kromer
Keyword(s):  
Ocean Circulation ◽  
Time Scale ◽  
Late Glacial ◽  
Minor Role ◽  
Activity Levels ◽  
Data Set ◽  
The Holocene ◽  
Spectral Interpretation ◽  
Late Glacial And Holocene ◽  
A Minor

AbstractLate-glacial and Holocene 14C/12C ratios of atmospheric CO2 vary in magnitude from a few per mil for annual/decadal pertubations to more than 10% for events lasting millennia. A data set illuminating 10- to 104-yr variability refines our understanding of oceanic (climatic) versus geomagnetic or solar forcing of atmospheric 14C/12C ratios. Most of the variance in the Holocene atmospheric 14C/12C record can be attributed to the geomagnetic (millennia time scale) and solar (century time scale) influence on the flux of primary cosmic rays entering the atmosphere. Attributing the observed atmospheric 14C/12C changes to climate alone leads to ocean circulation and/or global wind speed changes incompatible with proxy records. Climate-(ocean-)related 14C redistribution between carbon reservoirs, while evidently playing a minor role during the Holocene, may have perturbed atmospheric 14C/12C ratios measurably during the late-glacial Younger Dryas event. First-order corrections to the radiocarbon time scale (12,000–30,000 14C yr B.P.) are calculated from adjusted lake-sediment and tree-ring records and from geomagnetically defined model 14C histories. Paleosunspot numbers (100–9700 cal yr B.P.) are derived from the relationship of model 14C production rates to sunspot observations. The spectral interpretation of the 14C/12C atmospheric record favors higher than average solar activity levels for the next century. Minimal evidence was found for a sun-weather relationship.

Long-term variations in the geomagnetic activity level Part II: Ascending phases of sunspot cycles

1994 ◽  
Vol 12 (10/11) ◽  
pp. 1065-1070 ◽  
Author(s):  
V. Mussino ◽  
O. Borello Filisetti ◽  
M. Storini ◽  
H. Nevanlinna
Keyword(s):  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Activity Level ◽  
Activity Levels ◽  
Data Set ◽  
The Past ◽  
Long Term Trends ◽  
A Minor ◽  
Long Term Variations

Abstract. Monthly averages of the Helsinki Ak-values have been reduced to the equivalent aa-indices to extend the aa-data set back to 1844. A periodicity of about five cycles was found for the correlation coefficient (r) between geomagnetic indices and sunspot numbers for the ascending phases of sunspot cycles 9 to 22, confirming previous findings based on a minor number of sunspot cycles. The result is useful to researchers in topics related to solar-terrestrial physics, particularly for the interpretation of long-term trends in geomagnetic activity during the past, and to forecast geomagnetic activity levels in the future.

The extent, timing and palaeoclimatic significance of Late-glacial and Holocene snowpatches and glaciers in the Marrakech High Atlas, Morocco

2021 ◽  
Author(s):  
Benjamin Bell ◽  
Philip Hughes ◽  
William Fletcher ◽  
Roger Braithwaite ◽  
Henk Cornelissen ◽  
...  
Keyword(s):  
Little Ice Age ◽  
Late Glacial ◽  
Ice Age ◽  
High Atlas ◽  
The Holocene ◽  
Exposure Dating ◽  
Ground Water Recharge ◽  
Late Glacial And Holocene ◽  
High Level ◽  
Snow And Ice

<p>Pleistocene glaciers were extensive in the Marrakech High Atlas, Morocco. Today, semi-permanent snowpatches survive in topoclimatic settings and there is evidence of niche glaciers as recently as the Little Ice Age and early 20<sup>th</sup> Century. However, little is known about the state of permanent snow and niche glaciers through the Holocene. One hypothesis is that Little Ice Age glaciers were the largest snow and ice masses since the end of the Late-glacial (Younger Dryas 12.9-11.7 ka). Another possibility is that snow and ice expanded to similar or greater extents at other points in the Holocene.</p><p>To test these hypotheses, moraine boulders have been sampled on moraine successions in the highest parts of the High Atlas, including moraine successions in front of the névé permanent below the north-facing cliffs of Tazaghart (3890 m a.s.l.), a semi-permanent snowpatch that survives many summers today. This site is bounded by prominent moraine ridges with no soil development and no lichens on surface boulders. Several other high-level sites have been targeted and over 40 samples are currently being processed for <sup>10</sup>Be and <sup>36</sup>Cl exposure dating. Establishing the relative difference in extent and altitude of Late-glacial and the most recent glaciers in the High Atlas is important for understanding landscape and climate evolution in high mountain areas in the subtropics (31ºN).</p><p>The dated geomorphological records for late-lying snow and glaciers will be compared to high-resolution <sup>14</sup>C dated continuous parasequences from sediment cores from marshes at the Yagour Plateau and Oukaïmeden, both high-level sites in the High Atlas (~2700 m a.s.l.). The proximity of these sites (5-30 km, respectively) from the snowpatch/glacier sites will provide an important independent record of environmental change, spanning the Late-glacial and Holocene. This geomorphological record of former glaciers and snowpatches (moraines and pronival ramparts) is inherently fragmentary in time and the continuous core records from these alpine marshes will provide crucial insights into changing moisture conditions over time, which at these altitudes are closely related to the extent and volume of snowpack.</p><p>The climates associated with perennial snow cover and niche glaciers, and the associated annual snowpack melt, will be quantified using degree-day modelling. This allows melt rates to be predicted and this can be compared against observed modern climate in the High Atlas region. This involves interrogation of existing meteorological datasets from across the High Atlas and the development of algorithms for interpolation and extrapolation to ungauged higher altitudes.</p><p>Changes in the nature of the cryosphere through time in the High Atlas Mountains is crucial for understanding human activity and socioeconomic development in the wider region. Today, snowmelt from the High Atlas represents the most important ground water recharge used for a wide variety of purposes. Understanding changes in snow conditions, and as a consequence the behaviour of niche glaciers, in the High Atlas through the Holocene has important implications not only for water supply for humans but also for biological refugia and the evolution of cold-adapted flora and fauna.</p>

The Politics of Territorial Claims: A Geospatial Approach Applied to Africa

2016 ◽  
Vol 71 (1) ◽  
pp. 31-64 ◽  
Author(s):  
Hein E. Goemans ◽  
Kenneth A. Schultz
Keyword(s):  
Ethnic Groups ◽  
Colonial Period ◽  
Geospatial Data ◽  
Minor Role ◽  
Data Set ◽  
Secondary Role ◽  
Border Areas ◽  
Territorial Claims ◽  
A Minor ◽  
Analysis Of Variation

AbstractWhy do states make claims to some border areas and not others? We articulate three models of territorial claims and test them using a novel geospatial data set that precisely maps disputed and undisputed border segments in post-independence Africa. The geospatial approach helps eliminate problems of aggregation by permitting an analysis of variation both within and between dyadic borders. We find that ethnic political considerations are the most important driver of territorial claims in Africa, while institutional features of the border play a secondary role. Border segments that partition ethnic groups are at greatest risk of being challenged when the partitioned groups are politically powerful in ethnically homogeneous societies. Border segments that follow well-established and clear focal principles such as rivers and watersheds are significantly less likely to be disputed, while changes to the border in the colonial period created opportunities for later disputes to arise. Power considerations or resources play only a minor role in explaining the location of territorial claims.

Late glacial and Holocene glacier fluctuations at the Sub-Antarctic Island Kerguelen in the Southern Indian Ocean

2020 ◽  
Author(s):  
Jostein Bakke ◽  
Fabien Arnaud ◽  
Philip Deline ◽  
Charline Guiguet-Covex ◽  
Henriette Linge ◽  
...  
Keyword(s):  
Southern Ocean ◽  
Ocean Circulation ◽  
Sediment Cores ◽  
Critical Role ◽  
Late Glacial ◽  
Global Ocean ◽  
Exposure Dating ◽  
Temperature And Precipitation ◽  
Late Glacial And Holocene ◽  
Do So

<p>The Southern Hemisphere`s westerly winds play a critical role in regulating Earth`s climate by shielding Antarctica from low-latitude heat, driving global ocean circulation and regulate the uptake of CO2 in the Southern Ocean. Both strength and position of this globally significant atmospheric pattern are rapidly shifting in the face of ongoing global warming. A string of recent studies links these developments to dramatic coupled changes in temperature, precipitation, sea-ice coverage and glacier extent that unfold across the Southern Ocean region. Critically, a lack of baseline information restricts our ability to understand the causes and patterns of these shifts and represent them robustly in the future projections that underpin climate policies. To help do so, we utilize the sensitivity of glaciers to atmospheric climate change and the potential of glacier-fed lake sediments to record this signal through time. For this purpose, we integrate emerging sedimentological, geochemical and glacier modelling tools in a new method framework to reconstruct changes in glacier extent, temperature and precipitation on human-relevant timescales. To do so, we rely on a number of novel sedimentological and geochemical approaches. These include biomarker-based temperature reconstructions, exposure dating of moraines and the use emerging non-destructive scanning techniques (e.g. Computed Tomography – CT) to fingerprint depositional pathways. Our study area in this cross-disciplinary project is the poorly investigated sub-Antarctic Kerguelen Archipelago, well-situated in the core southern westerly wind belt. During an extensive 2019 field campaign, we collected 130 meters of sediment cores from six lakes, 110 rock samples for exposure dating and numerous catchment samples. </p>

Fluctuations of Outlet and Valley Glaciers in the Southern Andes (Argentina) during the Past 13,000 Years

1999 ◽  
Vol 51 (3) ◽  
pp. 238-247 ◽  
Author(s):  
Gerd Wenzens
Keyword(s):  
Younger Dryas ◽  
Late Glacial ◽  
The South ◽  
Southern Andes ◽  
Outlet Glacier ◽  
The Holocene ◽  
The Past ◽  
Late Glacial And Holocene ◽  
Glacial Time

AbstractIn the southern Argentine Andes, ten advances of valley glaciers were used to reconstruct the late-glacial and Holocene glacier history. The accumulation areas of these glaciers lie in the Precordillera and are thus independent of fluctuations of the South Patagonian Icefield. Like the Viedma outlet glacier, the valley glaciers advanced three times during late-glacial time (14,000–10,000 yr B.P.). The youngest advance correlates with the Younger Dryas Stade, based on two minimum AMS14C dates of 9588 and 9482 yr B.P. The second oldest advance occurred before 11,800 yr B.P. During the first half of the Holocene, (ca. 10,000–5000 yr B.P.), advances culminated about 8500, 8000–7500, and 5800–5500 yr B.P. During the second half of the Holocene, advances occurred between ca. 4500 and 4200 yr B.P., as well as between 3600 and 3300 yr B.P. In the Rı́o Cóndor valley three subsequent advances have been identified.

Late-glacial and Holocene vegetation and climatic history of the Cass Basin, central South Island, New Zealand

2004 ◽  
Vol 62 (3) ◽  
pp. 267-279 ◽  
Author(s):  
Matt S. McGlone ◽  
Chris S.M. Turney ◽  
Janet M. Wilmshurst
Keyword(s):  
New Zealand ◽  
Stable Carbon Isotopes ◽  
Ice Core ◽  
Late Glacial ◽  
Forest Patches ◽  
Climate Record ◽  
The North ◽  
Late Glacial And Holocene ◽  
A Minor ◽  
The Antarctic

Lithology, pollen, macrofossils, and stable carbon isotopes from an intermontane basin bog site in southern New Zealand provide a detailed late-glacial and early Holocene vegetation and climate record. Glacial retreat occurred before 17,000 cal yr B.P., and tundra-like grassland"shrubland occupied the basin shortly after. Between 16,500 and 14,600 cal yr B.P., a minor regional expansion of forest patches occurred in response to warming, but the basin remained in shrubland. Forest retreated between 14,600 and 13,600 cal yr B.P., at about the time of the Antarctic Cold Reversal. At 13,600 cal yr B.P., a steady progression from shrubland to tall podocarp forest began as the climate ameliorated. Tall, temperate podocarp trees replaced stress-tolerant shrubs and trees between 12,800 and 11,300 cal yr B.P., indicating sustained warming during the Younger Dryas Chronozone (YDC). Stable isotopes suggest increasing atmospheric humidity from 11,800 to 9300 cal yr B.P. Mild (annual temperatures at least 1°C higher than present), and moist conditions prevailed from 11,000 to 10,350 cal yr B.P. Cooler, more variable conditions followed, and podocarp forest was completely replaced by montane Nothofagus forest at around 7500 cal yr B.P. with the onset of the modern climate regime. The Cass Basin late-glacial climate record closely matches the Antarctic ice core records and is in approximate antiphase with the North Atlantic.

scholarly journals On the role of domain aspect ratio in the westward intensification of wind-driven surface ocean circulation

2020 ◽  
Author(s):  
Kaushal Gianchandani ◽  
Hezi Gildor ◽  
Nathan Paldor
Keyword(s):  
Aspect Ratio ◽  
Ocean Circulation ◽  
Minor Role ◽  
Western Boundary ◽  
Boundary Current ◽  
Damping Parameter ◽  
Two Parameters ◽  
A Minor ◽  
Analytical Expressions

Abstract. The two seminal studies on westward intensification, carried out by Stommel and Munk over 70 years ago, are revisited to elucidate the role of the domain aspect ratio (i.e. meridional to zonal extents of the basin) in determining the transport of the western boundary current (WBC). We examine the general mathematical properties of the two models by transforming them to differential problems that contain only two parameters – the domain aspect ratio and the non-dimensional damping (viscous) coefficient. Explicit analytical expressions are obtained from solutions of the non-dimensional vorticity equations and verified by long-time numerical simulations of the corresponding time-dependent equations. The analytical expressions as well as the simulations, imply that in Stommel's model both the domain aspect ratio and the damping parameter contribute equally to the non-dimensional transport of the WBC. On the other hand, in Munk's model the WBC's transport varies linear with the domain aspect ratio, while the damping parameter plays a minor role only. This finding is employed to explain the weak WBC in the South Pacific.

scholarly journals Multi-scale statistics of turbulence motorized by active matter

2017 ◽  
Vol 822 ◽  
pp. 762-773 ◽  
Author(s):  
J. Urzay ◽  
A. Doostmohammadi ◽  
J. M. Yeomans
Keyword(s):  
Turbulent Flows ◽  
Three Dimensional ◽  
Collective Effects ◽  
Minor Role ◽  
Activity Levels ◽  
Active Matter ◽  
Multi Scale ◽  
Spatio Temporal ◽  
High Reynolds ◽  
A Minor

A number of micro-scale biological flows are characterized by spatio-temporal chaos. These include dense suspensions of swimming bacteria, microtubule bundles driven by motor proteins and dividing and migrating confluent layers of cells. A characteristic common to all of these systems is that they are laden with active matter, which transforms free energy in the fluid into kinetic energy. Because of collective effects, the active matter induces multi-scale flow motions that bear strong visual resemblance to turbulence. In this study, multi-scale statistical tools are employed to analyse direct numerical simulations (DNS) of periodic two-dimensional (2-D) and three-dimensional (3-D) active flows and to compare the results to classic turbulent flows. Statistical descriptions of the flows and their variations with activity levels are provided in physical and spectral spaces. A scale-dependent intermittency analysis is performed using wavelets. The results demonstrate fundamental differences between active and high-Reynolds-number turbulence; for instance, the intermittency is smaller and less energetic in active flows, and the work of the active stress is spectrally exerted near the integral scales and dissipated mostly locally by viscosity, with convection playing a minor role in momentum transport across scales.

A smaller glacial ocean carbon inventory?

2021 ◽  
Author(s):  
Jun Shao ◽  
Lowell Stott ◽  
Andy Ridgwell ◽  
Ning Zhao ◽  
Florian Adolphi ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
Ice Core ◽  
Minor Role ◽  
Production Rates ◽  
Underlying Assumption ◽  
Ice Core Record ◽  
Ocean Carbon ◽  
A Minor ◽  
Good Coverage ◽  
The Last Glacial

<p>Previous studies attempting to explain Pleistocene atmospheric CO<sub>2</sub> variations have focused on mechanisms that transfer carbon (C) between the oceanic, atmospheric and terrestrial reservoirs, with the underlying assumption that the total C inventory in these three Earth’s surface reservoirs remained constant during glacial-interglacial cycles. Under this framework, ocean C inventory would have been marginally increased by 500-1000 GtC (1-2%) during the glacial period. Here, we show that past ocean C inventory can be revealed by reconstructed bulk ocean <sup>14</sup>C/<sup>12</sup>C (denoted as ∆<sup>14</sup>C) and atmospheric <sup>14</sup>C production rates with an Earth system model - cGENIE. First, we develop a bulk ocean ∆<sup>14</sup>C record that spans the last 40 ka from thousands of benthic foraminifera and deep sea coral ∆<sup>14</sup>C data with a fairly good coverage of the global seafloor. We then run cGENIE under constant pre-industrial boundary conditions, with the only forcing being atmospheric <sup>14</sup>C production rates reconstructed by geomagnetic field intensity records and ice core record of <sup>10</sup>Be fluxes. Under most of the <sup>14</sup>C production scenarios, the simulated bulk ocean ∆<sup>14</sup>C are significantly lower than our composite during the Last Glacial Maximum as well as the early deglaciation. Bulk ocean ∆<sup>14</sup>C is a metric controlled by <sup>14</sup>C production rates and ocean C inventory, with the state of ocean circulation playing a minor role.  Our finding suggests either glacial <sup>14</sup>C production was much higher and/or glacial C inventory was much lower than previously thought. Implications of both possibilities are discussed. In particular, the second possibility highlight the exchange of C and ALK between Earth’s surface and geological reservoirs as a critical missing piece in searching for a complete theory of glacial-interglacial atmospheric CO<sub>2 </sub>variability.</p>

scholarly journals On the role of domain aspect ratio in the westward intensification of wind-driven surface ocean circulation

Ocean Science ◽  
2021 ◽  
Vol 17 (1) ◽  
pp. 351-363
Author(s):  
Kaushal Gianchandani ◽  
Hezi Gildor ◽  
Nathan Paldor
Keyword(s):  
Aspect Ratio ◽  
Ocean Circulation ◽  
Damping Coefficient ◽  
Minor Role ◽  
Western Boundary ◽  
Boundary Current ◽  
Two Parameters ◽  
A Minor ◽  
Analytical Expressions

Abstract. The two seminal studies on westward intensification, carried out by Stommel and Munk over 70 years ago, are revisited to elucidate the role of the domain aspect ratio (i.e., meridional to zonal extents of the basin) in determining the transport of the western boundary current (WBC). We examine the general mathematical properties of the two models by transforming them to differential problems that contain only two parameters – the domain aspect ratio and the non-dimensional damping (viscous) coefficient. Explicit analytical expressions are obtained from solutions of the non-dimensional vorticity equations and verified by long-term numerical simulations of the corresponding time-dependent equations. The analytical expressions as well as the simulations imply that in Stommel's model both the domain aspect ratio and the damping parameter contribute to the non-dimensional transport of the WBC. However, the transport increases as a cubic power of the aspect ratio and decreases linearly with the damping coefficient. On the other hand, in Munk's model the WBC's transport increases linearly with the domain aspect ratio, while the damping coefficient plays a minor role only. This finding is employed to explain the weak WBC in the South Pacific. The decrease in transport of the WBC for small-domain aspect ratio results from the decrease in Sverdrup transport in the basin's interior because the meridional shear of the zonal velocity cannot be neglected as an additional vorticity term.

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