This study tested the utility of a variable mixing efficiency formulation proposed by Mashayek, et al. (2017) for use in oceanographic models other than the modern, pre-industrial ocean. This formulation is used to calculate diapycnal (vertical) mixing due to unresolved subgrid-scale processes. Results from Last Glacial Maximum (LGM) simulations for...
During the Last Glacial Maximum (LGM, ∼ 21 ky before present) the atmospheric CO2 concentration was about 100 ppm lower than its pre-industrial (PI)value. The missing carbon from the atmosphere must have been stored in thedeep ocean during this period, but the mechanisms driving such re-distribution ofthe carbon cycle are...
We present a new nitrogen isotope model incorporated into the three-dimensional ocean component of a global Earth System Climate Model designed for millennial timescale simulations. The model includes prognostic tracers for the stable nitrogen isotopes, ¹⁴N and ¹⁵N, in the nitrate (NO₃ˉ), phytoplankton, zooplankton, and detritus variables of the marine...
Over the last 150 years, Oregon white oak habitat in the Willamette Valley has been converted to support grass crops, orchards and vineyards, cities, and conifer forests, nearly extirpating it from the Willamette Valley. Yet Oregon white oak offers many ecosystem services to the Willamette Valley and its residents. Recent...
The El Niño/Southern Oscillation (ENSO) affects millions of people via global teleconnections in the form of drought and torrential rainfall that impact agriculture and food production in many countries. Yet how ENSO will respond to a warming world is uncertain and a greatly debated topic. The Intergovernmental Panel on Climate...
Earth's climate and the concentrations of the atmospheric greenhouse gases carbon dioxide (CO2) and nitrous oxide (N2O) varied strongly on millennial timescales during past glacial periods. Large and rapid warming events in Greenland and the North Atlantic were followed by more gradual cooling, and are highly correlated with fluctuations of...
Glacial periods exhibit abrupt Dansgaard-Oeschger (DO) climatic oscillations that are thought to be linked to instabilities in the Atlantic meridional overturning circulation (AMOC). Great uncertainty remains regarding the dynamics of the DO cycle, as well as controls on the timing and duration of individual events. Using ice core data we...
Previous Paleoclimate Model Intercomparison Project (PMIP) simulations of the Last Glacial Maximum (LGM) Atlantic Meridional Overturning Circulation (AMOC) showed dissimilar results on transports and structure. Here we analyze the most recent PMIP3 models, which show a consistent increase (on average by 41 ± 26%) and deepening (663 ± 550 m)...
Full Text:
Muglia, J., & Schmittner, A. (2015). Glacial Atlantic overturning increased by wind
stress in climate
Previous Paleoclimate Model Intercomparison Project (PMIP) simulations of the Last Glacial Maximum (LGM) Atlantic Meridional Overturning Circulation (AMOC) showed dissimilar results on transports and structure. Here we analyze the most recent PMIP3 models, which show a consistent increase (on average by 41 ± 26%) and deepening (663 ± 550 m)...
Full Text:
Atlantic overturning
increased by wind stress in climate models”
Juan Muglia1 and Andreas Schmittner1
Previous Paleoclimate Model Intercomparison Project (PMIP) simulations of the Last Glacial Maximum (LGM) Atlantic Meridional Overturning Circulation (AMOC) showed dissimilar results on transports and structure. Here we analyze the most recent PMIP3 models, which show a consistent increase (on average by 41 ± 26%) and deepening (663 ± 550 m)...
As climate change and its associated environmental and socioeconomic impacts become increasingly severe and imminent across the United States, it has become imperative for the public to be aware of and actively engaged with this issue. Although scientists generally perceive outreach in a positive light, a critical barrier that tends...
In the 1954 John Nash [1] showed, through use of an iterative scheme of approximate embedding maps, that the sphere S² could be isometrically embedded into a ball of any radius by a C¹ map. In the 1980's M. Gromov [2] generalized Nash's work to the h-principal and convex integration....
In this work, we consider a convexity splitting scheme for a coupled phase field and energy equation, a modification of Stefan problem. The Stefan problem is a free boundary value problem that models the temperature in a homogeneous multiphase medium. Each phase is modeled using a heat diffusion parabolic partial...
For spatial data visualization, we approach two problems and provide solutions: heat map resolution selection, and heat map confidence interval presentation. Analysts often present spatial data in gridded heat maps, at some chosen resolution. However, many data types vary in density across the domain. We develop variable-resolution heat maps to...
In this work, we provide a detailed analysis of a discrete time regime switching financial market model with jumps. We consider the model under two different scenarios: known and unknown initial regime. For each scenario we investigated conditions that guarantee the model's completeness. We find that the model under consideration...
This thesis presents the results of an investigation into the measured and modeled
mass balance of the Collier Glacier, a small (0.70 km²), valley glacier located in the
Oregon Cascade Range (44° 10' N, 121° 47' W). Here we present mass-balance
measurements conducted for the 2009 and 2010 balance years...
Water is one of the most biologically and economically important substances on Earth. A significant portion of Earth's water subsists in the subsurface. Our ability to monitor the flow and transport of water and other fluids through this unseen environment is crucial for a myriad of reasons.
One difficulty we...
Most climate models predict a weakening of the North Atlantic thermohaline circulation for the 21st century when forced by increasing levels of greenhouse gas concentrations. The model spread, however, is rather large, even when the forcing scenario is identical, indicating a large uncertainty in the response to forcing. In order...
A coupled climate-carbon cycle model and ice core CO2 data from the last glacial
period are used to explore the impact of changes in ocean circulation on atmospheric
CO2 concentrations on millennial time scales. In the model, stronger wind
driven circulation increases atmospheric CO2. Changes in the buoyancy driven
deep...
Climate models predict a gradual weakening of the North Atlantic meridional overturning circulation (MOC) during the twenty-first century due to increasing levels of greenhouse gas concentrations in the atmosphere. Using an ensemble of 16 different coupled climate models performed for the Fourth Assessment Report (AR4) of the Intergovernmental Panel on...