Long-Term Climate Stability

2021 ◽  
pp. 32-56
Keyword(s):  
Climate Stability

scholarly journals Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

2021 ◽  
Author(s):  
◽  
Maia Bellingham
Keyword(s):  
Carbon Dioxide ◽  
New Zealand ◽  
Chemical Weathering ◽  
Southern Alps ◽  
Grain Sizes ◽  
Denudation Rates ◽  
Climate Stability ◽  
Mountain Landscapes ◽  
Carbon Dioxide Cycling

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood.   To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering.   Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments.   Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

scholarly journals Phylogenetic age differences in tree assemblages across the Northern Hemisphere increase with long-term climate stability in unstable regions

2017 ◽  
Vol 26 (9) ◽  
pp. 1035-1042 ◽  
Author(s):  
Gang Feng ◽  
Ziyu Ma ◽  
Blas M. Benito ◽  
Signe Normand ◽  
Alejandro Ordonez ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Age Differences ◽  
Climate Stability ◽  
Tree Assemblages

scholarly journals Secular spin-axis dynamics of exoplanets

2019 ◽  
Vol 623 ◽  
pp. A4 ◽  
Author(s):  
M. Saillenfest ◽  
J. Laskar ◽  
G. Boué
Keyword(s):  
Major Axis ◽  
Orbital Evolution ◽  
Spin Axis ◽  
Semi Major Axis ◽  
Resonance Overlap ◽  
Climate Stability ◽  
Dynamical Parameters ◽  
Analytical Formulas ◽  
Quantitative Results

Context. Seasonal variations and climate stability of a planet are very sensitive to the planet obliquity and its evolution. This is of particular interest for the emergence and sustainability of land-based life, but orbital and rotational parameters of exoplanets are still poorly constrained. Numerical explorations usually realised in this situation are therefore in heavy contrast with the uncertain nature of the available data. Aims. We aim to provide an analytical formulation of the long-term spin-axis dynamics of exoplanets, linking it directly to physical and dynamical parameters, but still giving precise quantitative results if the parameters are well known. Together with bounds for the poorly constrained parameters of exoplanets, this analysis is designed to enable a quick and straightforward exploration of the spin-axis dynamics. Methods. The long-term orbital solution is decomposed into quasi-periodic series and the spin-axis Hamiltonian is expanded in powers of eccentricity and inclination. Chaotic zones are measured by the resonance overlap criterion. Bounds for the poorly known parameters of exoplanets are obtained from physical grounds (rotational breakup) and dynamical considerations (equipartition of the angular momentum deficit). Results. This method gives accurate results when the orbital evolution is well known. The detailed structure of the chaotic zones for the solar system planets can be retrieved from simple analytical formulas. For less-constrained planetary systems, the maximal extent of the chaotic regions can be computed, requiring only the mass, the semi-major axis, and the eccentricity of the planets present in the system. Additionally, some estimated bounds of the precession constant allow to classify which observed exoplanets are necessarily out of major spin-orbit secular resonances (unless the precession rate is affected by the presence of massive satellites).

scholarly journals Accumulation over evolutionary time as a major cause of biodiversity hotspots in conifers

2019 ◽  
Vol 286 (1912) ◽  
pp. 20191887 ◽  
Author(s):  
Mekala Sundaram ◽  
Michael J. Donoghue ◽  
Aljos Farjon ◽  
Denis Filer ◽  
Sarah Mathews ◽  
...  
Keyword(s):  
Species Richness ◽  
Biodiversity Hotspots ◽  
Primary Role ◽  
Mountainous Areas ◽  
Evolutionary Time ◽  
Phylogenetic Structure ◽  
Climate Stability ◽  
High Species Richness ◽  
Plant Endemism

Biodiversity hotspots are important for understanding how areas of high species richness form, but disentangling the processes that produce them is difficult. We combine geographical ranges, phylogenetic relationships and trait data for 606 conifer species in order to explore the mechanisms underlying richness hotspot formation. We identify eight richness hotspots that overlap known centres of plant endemism and diversity, and find that conifer richness hotspots occur in mountainous areas within broader regions of long-term climate stability. Conifer hotspots are not unique in their species composition, traits or phylogenetic structure; however, a large percentage of their species are not restricted to hotspots and they rarely show either a preponderance of new radiating lineages or old relictual lineages. We suggest that conifer hotspots have primarily formed as a result of lineages accumulating over evolutionary time scales in stable mountainous areas rather than through high origination, preferential retention of relictual lineages or radiation of species with unique traits, although such processes may contribute to nuanced differences among hotspots. Conifers suggest that a simple accumulation of regional diversity can generate high species richness without additional processes and that geography rather than biology may play a primary role in hotspot formation.

Human-induced prehistoric soil buried in the flood plain of Svratka River, Czech Republic

The Holocene ◽  
2019 ◽  
Vol 29 (4) ◽  
pp. 565-577 ◽  
Author(s):  
Lenka Vejrostová ◽  
Lenka Lisá ◽  
David Parma ◽  
Aleš Bajer ◽  
Mária Hajnalová ◽  
...  
Keyword(s):  
Bronze Age ◽  
Flood Plain ◽  
Natural Setting ◽  
Human Settlement ◽  
Climate Stability ◽  
Subsequent Period ◽  
Buried Soil ◽  
Points Of View ◽  
Multiproxy Approach

The natural setting and prehistoric human activity on Holocene floodplains in Central Europe is a compelling issue from several points of view. This environment presents an important sedimentary archive reflecting past human behaviour in interactions with climate change. Two sedimentary sections recorded in the alluvial zone of Svratka River (Moravia) with a buried soil dated to the time span between the Neolithic and Late Bronze Age, and comprising one paleo-catena, were investigated using a multiproxy approach. The buried paleo-catena presents evidence of long-term (ancient) soil development, and the use of the site for human settlement and farming ca. 4500 BC until 1000 BC. Buried soil horizons indicate (climate) stability, which according to archaeological evidence lasted for at least 3500 years, until at least 1000 BC. The architecture and the lithology of the river floodplain changes approximately 0 AD. Anthropogenic settlement activity was not detected at the site in the subsequent period, and this is very likely to be associated with increased sedimentation rates and less optimal conditions for human settlement.

Geography of Subterranean Biodiversity

2019 ◽  
pp. 179-205
Author(s):  
David C. Culver ◽  
Tanja Pipan
Keyword(s):  
High Surface ◽  
Habitat Availability ◽  
Southern Europe ◽  
Southeast United States ◽  
Small Component ◽  
Dinaric Karst ◽  
Local Diversity ◽  
Climate Stability ◽  
Surface Productivity

Globally, for troglobionts, southern Europe, especially the Dinaric karst, and the Canary Islands are regions of high richness. For stygobionts, southern Europe, especially the Dinaric karst, is a hotspot. Other sites are typically chemoautotrophic and/or phreatic. In Europe and North America, there appears to be a ridge of high troglobiotic and stygobiotic diversity in southern Europe and the southeast United States that corresponds to an area of long-term high surface productivity. In Europe, local diversity is a small component of regional stygobiotic diversity and the importance of spatial heterogeneity, historical climate stability, and productivity are both scale and spatially dependent. Habitat availability seems especially important at smaller scales. The analogy with islands in ecological time is most appropriate at scales smaller than caves, such as seeps or epikarst drips, and the analogy with caves in evolutionary time is more appropriate at larger scales, such as karst basins or contiguous karst areas.

Earth-like worlds on eccentric orbits: excursions beyond the habitable zone

2002 ◽  
Vol 1 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Darren M. Williams ◽  
David Pollard
Keyword(s):  
General Circulation ◽  
Climate Model ◽  
Three Dimensional ◽  
Balance Model ◽  
Seasonal Temperature ◽  
Habitable Zone ◽  
One Dimensional ◽  
Climate Stability ◽  
Eccentric Orbits

Many of the recently discovered extrasolar giant planets move around their stars on highly eccentric orbits, and some with e [ges ] 0·7. Systems with planets within or near the habitable zone (HZ) will possibly harbour life on terrestrial-type moons if the seasonal temperature extremes resulting from the large orbital eccentricities of the planets are not too severe. Here we use a three-dimensional general-circulation climate model and a one-dimensional energy-balance model to examine the climates of either bound or isolated earths on extremely elliptical orbits near the HZ. While such worlds are susceptible to large variations in surface temperature, long-term climate stability depends primarily on the average stellar flux received over an entire orbit, not the length of the time spent within the HZ.

scholarly journals Climatic effects on rapid chemical and physical denudation rates measured with cosmogenic nuclides in the Ōhau catchment, New Zealand

2021 ◽  
Author(s):  
◽  
Maia Bellingham
Keyword(s):  
Carbon Dioxide ◽  
New Zealand ◽  
Chemical Weathering ◽  
Southern Alps ◽  
Grain Sizes ◽  
Denudation Rates ◽  
Climate Stability ◽  
Mountain Landscapes ◽  
Carbon Dioxide Cycling

<p>Understanding how active mountain landscapes contribute to carbon dioxide cycling and influences on long-term climate stability requires measurement of weathering fluxes from these landscapes. The few measured chemical weathering rates in the Southern Alps are an order of magnitude greater than in the rest of the world. Rapid tectonic uplift coupled with extreme orographic precipitation is driving exceptionally fast chemical and physical denudation. These rates suggest that weathering in landscapes such as the Southern Alps could play a significant role in carbon dioxide cycling. However, the relative importance of climate and tectonics driving these fast rates remains poorly understood.   To address this gap, in situ ¹⁰Be derived catchment-averaged denudation rates were measured in the Ōhau catchment, Canterbury, New Zealand. Denudation rates in the Dobson Valley within the Ōhau catchment, varied from 474 – 7,570 m Myr⁻¹, aside from one sub-catchment in the upper Dobson Valley that had a denudation rate of 12,142 m Myr⁻¹. The Dobson and Hopkins Rivers had denudation rates of 1,660 and 4,400 m Myr⁻¹ respectively, in these catchments. Dobson Valley denudation rates show a moderate correlation with mean annual precipitation (R²=0.459). This correlation supports a similar trend identified at local and regional scales, and at high rates of precipitation this may be an important driver of erosion and weathering.   Sampling of four grain sizes (0.125 to > 8 mm) at one site in the Dobson Valley resulted in variability in ¹⁰Be concentrations up to a factor of 2.5, which may be a result of each grain size recording different erosional processes. These observations demonstrate the importance of assessing potential variability and the need to sample consistent grain sizes across catchments.   Chemical depletion fractions measured within soil pits in the upper Dobson Valley indicate chemical weathering contributes 30% of total denudation, and that physical erosion is driving rapid total denudation. Chemical weathering appears to surpass any proposed weathering speed limit and suggests total weathering may not be limited by weathering kinetics. This research adds to the paucity of research in New Zealand, and for the first time presents ¹⁰Be derived denudation rates from the eastern Southern Alps, with estimates of the long-term weathering flux. High weathering fluxes in the Southern Alps uphold the hypothesis that mountain landscapes play an important role in carbon dioxide cycling and long-term climate stability.</p>

scholarly journals Future Regional Contributions for Climate Change Mitigation: Insights from Energy Investment Gap and Policy Cost

2019 ◽  
Vol 11 (12) ◽  
pp. 3341
Author(s):  
Hongjie Sun ◽  
Shuwen Niu ◽  
Xiqiang Wang
Keyword(s):  
Climate Change ◽  
Climate Change Mitigation ◽  
Developing Regions ◽  
Energy Investment ◽  
Global Energy ◽  
Climate Stability ◽  
The Future ◽  
Policy Cost ◽  
Change Mitigation

Mitigating climate change and ensuring regional equity development is equitable are matters of global concern. Systematic and in-depth research into theseissues is seldom conducted. In this research we combine qualitative and quantitative studies and use six state-of-the-art energy-economy analysis models and four long term scenarios to explore the distribution of regional contributions for climate change mitigation in the future. We focus on the energy investment gap and policy cost. The study’s conclusion is that, under the assumption of carbon tax as a source of energy investment from 2025, the global positive energy investment gap in the climate change mitigation scenario will not appear until around 2035–2040. Asia and OECD90+EU (Countries from the OECD 1990, EU and its candidates) are the regions that will have a significant direct impact on the global energy investment gap under climate policies in the future. However, from the perspective of the relative value (the percentage of the energy investment gap relative to the energy investment in the Current Policies (CPol) scenario), Asia will contribute the most to the global energy investment gap under the climate stability policies. Under the Nationally Determined Contributions (NDC) scenario, Asia will contribute the most in the near term and REF will contribute the most in the medium term.The findings show that OECD90+EUwill bear more cost in the pledges scenario, and Asia will bear more cost in the climate stability scenarios in the medium term. Contrary to the common sense expectation, the developed regions will contribute the least in terms of the proportion of the policy cost to the respective economic aggregates under the climate stability scenarios in the medium and long term, but the opposite is true in the developing regions. By and large, from the perspective of the current climate change mitigation policies, the developed regions and developing regions will achieve a win-win situation in the long run, but the relative contribution of the developed regions is not as great as was previously expected. These novel findings should prove to be useful to policy makers when developing transition strategies for climate change mitigation.

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