Now showing items 21-40 of 80

• #### A Depth-Derived Pleistocene Age-Model: Uncertainty Estimates, Sedimentation Variability, and Nonlinear Climate Change ﻿

(American Geophysical Union, 2004)
A new chronology of glaciation, spanning the last 780,000 years, is estimated from 21 marine sediment cores using depth as a proxy for time. To avoid biasing this ‘‘depth-derived’’ age estimate, the depth scale is first ...
• #### A detection of Milankovitch frequencies in global volcanic activity ﻿

(Geological Society of America, 2013)
A rigorous detection of Milankovitch periodicities in volcanic output across the Pleistocene-Holocene ice age has remained elusive. We report on a spectral analysis of a large number of well-preserved ash plume deposits ...
• #### Early Pleistocene Glacial Cycles and the Integrated Summer Insolation Forcing ﻿

(American Association for the Advancement of Science, 2006)
Long-term variations in Northern Hemisphere summer insolation are generally thought to control glaciation. But the intensity of summer insolation is primarily controlled by 20,000-year cycles in the precession of the ...
• #### Earth rotation changes since ?500 CE driven by ice mass variations ﻿

(Elsevier BV, 2016)
We predict the perturbation to the Earth's length-of-day (LOD) over the Common Era using a recently derived estimate of global sea-level change for this time period. We use this estimate to derive a time series of “clock ...
• #### An enigma in estimates of the Earth's dynamic ellipticity ﻿

(Oxford University Press, 2012)
The precession and obliquity frequencies of the Earth’s rotational motion are functions of the dynamic ellipticity of the Earth’s gravitational figure, and this connection has provided a novel bridge between studies of ...
• #### Estimation of Spectral Power Laws in Time-Uncertain Series of Data with Application to the GISP2 $δ^{18}$O Record ﻿

(American Geophysical Union, 2011)
Errors in the timing assigned to observations degrade estimates of the power spectrum in a complicated and nonlocal fashion. It is clear that timing errors will smear concentrations of spectral energy across a wide band ...
• #### Evolution of a Coupled Marine Ice Sheet–Sea Level Model ﻿

(American Geophysical Union, 2012)
We investigate the stability of marine ice sheets by coupling a gravitationally self-consistent sea level model valid for a self-gravitating, viscoelastically deforming Earth to a 1-D marine ice sheet-shelf model. The ...
• #### Feedback Between Deglaciation, Volcanism, and Atmospheric CO2 ﻿

(Elsevier, 2009)
An evaluation of the historical record of volcanic eruptions shows that subaerial volcanism increases globally by two to six times above background levels between 12 ka and 7 ka, during the last deglaciation. Increased ...
• #### Frequent summer temperature extremes reflect changes in the mean, not the variance ﻿

(Proceedings of the National Academy of Sciences, 2013)
• #### Glacial cycles drive variations in the production of oceanic crust ﻿

(American Association for the Advancement of Science (AAAS), 2015)
Glacial cycles redistribute water between oceans and continents, causing pressure changes in the upper mantle, with consequences for the melting of Earth’s interior. Using Plio-Pleistocene sea-level variations as a forcing ...
• #### Glacial Variability Over the Last Two Million Years: An Extended Depth-Derived Agemodel, Continuous Obliquity Pacing, and the Pleistocene Progression ﻿

(Elsevier, 2007)
An agemodel not relying upon orbital assumptions is estimated over the last 2 Ma using depth in marine sediment cores as a proxy for time. Agemodel uncertainty averages +/- 10 Ka in the early Pleistocene (similar to 2-1 ...
• #### Global and regional variability in marine surface temperatures ﻿

(Wiley-Blackwell, 2014)
The temperature variability simulated by climate models is generally consistent with that observed in instrumental records at the scale of global averages, but further insight can also be obtained from regional analysis ...
• #### Global change: Interglacial and future sea level ﻿

(Nature Publishing Group, 2009)
A merger of data and modelling using a probabilistic approach indicates that sea level was much higher during the last interglacial than it is now, providing telling clues about future ice-sheet responses to warming.
• #### Heterogeneous warming of Northern Hemisphere surface temperatures over the last 1200 years ﻿

(Wiley-Blackwell, 2015)
The relationship between the mean and spatial variability of Northern Hemisphere surface temperature anomalies over the last 1200 years is examined using instrumental and proxy records. Nonparametric statistical tests ...
• #### How is the ocean filled? ﻿

(Wiley-Blackwell, 2011)
The ocean surface rapidly exchanges heat, freshwater, and gases with the atmosphere, but once water sinks into the ocean interior, the inherited properties of seawater are closely conserved. Previous water-mass decompositions ...
• #### Identification and interpretation of nonnormality in atmospheric time series ﻿

(Wiley-Blackwell, 2016)
Nonnormal characteristics of geophysical time series are important determinants of extreme events and may provide insight into the underlying dynamics of a system. The structure of nonnormality in winter temperature is ...
• #### Impacts of elevated atmospheric CO2 on nutrient content of important food crops ﻿

(Nature Publishing Group, 2015)
One of the many ways that climate change may affect human health is by altering the nutrient content of food crops. However, previous attempts to study the effects of increased atmospheric CO2 on crop nutrition have been ...
• #### Imprints of Geodynamic Processes on the Paleoclimate Record ﻿

(2016-05-18)
In this thesis I investigate how solid Earth deformation associated with glacial isostatic adjustment and mantle convection impacted ice age climate. In particular, I discard approximations that treat the Earth's internal ...
• #### Increasing CO2 threatens human nutrition ﻿

(Nature Publishing Group, 2014)
Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies1, causing a loss of 63 million life-years annually2, 3. Most of these people ...
• #### Integrated Summer Insolation Forcing and 40,000-Year Glacial Cycles: The Perspective from an Ice-Sheet/Energy-Balance Model ﻿

(American Geophysical Union, 2008)
Although the origins of the 40,000-year glacial cycles during the early Pleistocene are readily attributed to changes in Earth's obliquity (also having a 40,000-year period), the lack of ice-volume variability at precession ...