Index Catalog // ScholarsArchive@OSU

Last Century Warming Over the Canadian Atlantic Shelves Linked to Weak Atlantic Meridional Overturning Circulation

Creator:: Thibodeau, Benoit, Not, Christelle, Hu, Jiang, Schmittner, Andreas, Noone, David, Tabor, Clay, Zhang, Jiaxu, and Liu, Zhengyu
Abstract:: The Atlantic meridional overturning circulation (AMOC) is a key component of the global climate system. Recent studies suggested a twentieth-century weakening of the AMOC of unprecedented amplitude (similar to 15%) over the last millennium. Here we present a record of O-18 in benthic foraminifera from sediment cores retrieved from the...
Resource Type:: Article

What is the skill of ocean tracers in reducing uncertainties about ocean diapycnal mixing and projections of the Atlantic Meridional Overturning Circulation?

Creator:: Schmittner, Andreas, Tonkonojenkov, Roman, Urban, Nathan M., Goes, Marlos, Haran, Murali, and Keller, Klaus
Abstract:: Current projections of the oceanic response to anthropogenic climate forcings are uncertain. Two key sources of these uncertainties are (1) structural errors in current Earth system models and (2) imperfect knowledge of model parameters. Ocean tracer observations have the potential to reduce these uncertainties. Previous studies typically consider each tracer...
Resource Type:: Article

Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations

Creator:: Schmittner, Andreas, Latif, M., and Schneider, B.
Abstract:: 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...
Resource Type:: Article

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water Subduction: Paleoceanography

Creator:: Schmittner, Andreas, Galbraith, Eric D., Hostetler, Steven W., Pedersen, Thomas F., and Zhang, Rong
Abstract:: Paleoclimate records from glacial Indian and Pacific oceans sediments document millennial-scale fluctuations of subsurface dissolved oxygen levels and denitrification coherent with North Atlantic temperature oscillations. Yet the mechanism of this teleconnection between the remote ocean basins remains elusive. Here we present model simulations of the oxygen and nitrogen cycles that...
Resource Type:: Article

Changes in equatorial Pacific thermocline depth in response to Panamanian seaway closure: Insights from a multi-model study

Creator:: Zhang, Xiao, Prange, Matthias, Steph, Silke, Butzin, Martin, Krebs, Uta, Lunt, Daniel J., Nisancioglu, Kerim H., Park, Wonsun, Schmittner, Andreas, Schneider, Birgit, and Schulz, Michael
Abstract:: The early Pliocene warm phase was characterized by high sea surface temperatures and a deep thermocline in the eastern equatorial Pacific. A new hypothesis suggests that the progressive closure of the Panamanian seaway contributed substantially to the termination of this zonally symmetric state in the equatorial Pacific. According to this...
Resource Type:: Article

Abrupt change in atmospheric CO₂ during the last ice age

Creator:: Ahn, Jinho, Brook, Edward J., Schmittner, Andreas, and Kreutz, Karl
Abstract:: During the last glacial period atmospheric carbon dioxide and temperature in Antarctica varied in a similar fashion on millennial time scales, but previous work indicates that these changes were gradual. In a detailed analysis of one event we now find that approximately half of the CO₂ increase that occurred during...
Resource Type:: Article

Nonlinearity of carbon cycle feedbacks

Creator:: Zickfeld, Kirsten, Eby, Michael, Matthews, H. Damon, Schmittner, Andreas, and Weaver, Andrew J.
Abstract:: Coupled climate–carbon models have shown the potential for large feedbacks between climate change, atmospheric CO₂ concentrations, and global carbon sinks. Standard metrics of this feedback assume that the response of land and ocean carbon uptake to CO₂ (concentration–carbon cycle feedback) and climate change (climate–carbon cycle feedback) combine linearly. This study...
Resource Type:: Article

Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean

Creator:: Somes, Christopher J., Schmittner, Andreas, and Altabet, Mark A.
Abstract:: Nitrogen (N) fixation by specialized microorganisms (diazotrophs) influences global plankton productivity because it provides the ocean with most of its bio-available N. However, its global rate and large-scale spatial distribution is still regarded with considerable uncertainty. Here we use a global ocean nitrogen isotope model, in comparison with δ15NO3 observations,...
Resource Type:: Article

What is the skill of ocean tracers in reducing uncertainties about ocean diapycnal mixing and projections of the Atlantic Meridional Overturning Circulation?

Creator:: Goes, Marlos, Urban, Nathan M., Tonkonojenkov, Roman, Haran, Murali, Schmittner, Andreas, and Keller, Klaus
Abstract:: Current projections of the oceanic response to anthropogenic climate forcings are uncertain. Two key sources of these uncertainties are (1) structural errors in current Earth system models and (2) imperfect knowledge of model parameters. Ocean tracer observations have the potential to reduce these uncertainties. Previous studies typically consider each tracer...
Resource Type:: Article

Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates

Creator:: Sarnthein, Michael, Bartoli, Greta, Prange, Michael, Schmittner, Andreas, Schneider, Birgit, Weinelt, Mara, Andersen, N., and Garbe-Schönberg, D.
Abstract:: A major tipping point of Earth's history occurred during the mid-Pliocene: the onset of major Northern-Hemisphere Glaciation (NHG) and of pronounced, Quaternary-style cycles of glacial-to-interglacial climates, that contrast with more uniform climates over most of the preceding Cenozoic and continue until today (Zachos et al., 2001). The severe deterioration of...
Resource Type:: Article

Southern Ocean control of glacial AMOC stability and Dansgaard-Oeschger interstadial duration

Creator:: Buizert, Christo and Schmittner, Andreas
Abstract:: 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...
Resource Type:: Article

Glacial Atlantic overturning increased by wind stress in climate models

Creator:: Muglia, Juan and Schmittner, Andreas
Abstract:: 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)...
Resource Type:: Article

Climate Sensitivity Estimated From Temperature Reconstructions of the Last Glacial Maximum

Creator:: Schmittner, Andreas, Urban, Nathan M., Shakun, Jeremy D., Mahowald, Natalie M., Clark, Peter U., Bartlein, Patrick J., Mix, Alan C., and Rosell-Mele, Antoni
Abstract:: Assessing impacts of future anthropogenic carbon emissions is currently impeded by uncertainties in our knowledge of equilibrium climate sensitivity to atmospheric carbon dioxide doubling. Previous studies suggest 3 K as best estimate, 2–4.5 K as the 66% probability range, and non-zero probabilities for much higher values, the latter implying a...
Resource Type:: Article

Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change

Creator:: Ross, Andrew, Matthews, H. Damon, Schmittner, Andreas, and Kothavala, Zavareh
Abstract:: The range in the projections of future climate warming can be attributed to the inherent uncertainty in the representation of climate model parameters and processes. In this study, we assess the effect of uncertainty in climate sensitivity and ocean heat uptake on the rate of future climate change. We apply...
Resource Type:: Article

A review of nitrogen isotopic alteration in marine sediments

Creator:: Robinson, Rebecca S., Kienast, Markus, Albuquerque, Ana Luiza, Altabet, Mark, Contreras, Sergio, De Pol Holz, Ricardo, Dubois, Nathalie, Francois, Roger, Galbraith, Eric, Hsu, Ting-Chang, Ivanochko, Tara, Jaccard, Samuel, Kao, Shuh-Ji, Kiefer, Thorsten, Kienast, Stephanie, Lehmann, Moritz, Martinez, Philippe, McCarthy, Matthew, Mobius, Jurgen, Pedersen, Tom, Quan, Tracy M., Ryabenko, Evgeniya, Schmittner, Andreas, Schneider, Ralph, Schneider-Mor, Aya, Shigemitsu, Masahito, Sinclair, Dan, Somes, Christopher, Studer, Anja, Thunell, Robert, and Yang, Jin-Yu
Abstract:: Nitrogen isotopes are an important tool for evaluating past biogeochemical cycling from the paleoceanographic record. However, bulk sedimentary nitrogen isotope ratios, which can be determined routinely and at minimal cost, may be altered during burial and early sedimentary diagenesis, particularly outside of continental margin settings. The causes and detailed mechanisms...
Resource Type:: Article

Evaluation of Different Methods to Assess Model Projections of the Future Evolution of the Atlantic Meridional Overturning Circulation

Creator:: Schneider, Birgit, Latif, M., and Schmittner, Andreas
Abstract:: 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...
Resource Type:: Article

Effects of Mountains and Ice Sheets on Global Ocean Circulation

Creator:: Schmittner, Andreas, Silva, Tiago A. M., Fraedrich, Klaus, Kirk, Edilbert, and Lunkeit, Frank
Abstract:: The impact of mountains and ice sheets on the large-scale circulation of the world’s oceans is investigated in a series of simulations with a new coupled ocean–atmosphere model [Oregon State University–University of Victoria model (OSUVic)], in which the height of orography is scaled from 1.5 times the actual height (at...
Resource Type:: Article

Simulating the global distribution of nitrogen isotopes in the ocean

Creator:: Somes, Christopher J., Schmittner, Andreas, Galbraith, Eric D., Lehmann, Moritz F., Altabet, Mark A., Montoya, Joseph P., Letelier, Ricardo M., Mix, Alan C., Bourbonnais, Annie, and Eby, Michael
Abstract:: 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 two stable nitrogen isotopes, 14N and 15N, in the nitrate (NO3−), phytoplankton, zooplankton, and detritus variables of the...
Resource Type:: Article

Glacial greenhouse-gas fluctuations controlled by ocean circulation changes

Creator:: Schmittner, Andreas and Galbraith, Eric D.
Abstract:: 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...
Resource Type:: Article

Using tracer observations to reduce the uncertainty of ocean diapycnal mixing and climate–carbon cycle projections

Creator:: Schmittner, Andreas, Urban, Nathan M., Keller, Klaus, and Matthews, Damon
Abstract:: What is the uncertainty of climate-carbon cycle projections in response to anthropogenic greenhouse gas emissions and how can we reduce this uncertainty? We address this question by quantifying the ability of available ocean tracer observations to constrain the values of diapycnal diffusivity in the pelagic ocean (Kv), a key uncertain...
Resource Type:: Article

ScholarsArchive@OSU

Last Century Warming Over the Canadian Atlantic Shelves Linked to Weak Atlantic Meridional Overturning Circulation

What is the skill of ocean tracers in reducing uncertainties about ocean diapycnal mixing and projections of the Atlantic Meridional Overturning Circulation?

Model projections of the North Atlantic thermohaline circulation for the 21st century assessed by observations

Large fluctuations of dissolved oxygen in the Indian and Pacific oceans during Dansgaard-Oeschger oscillations caused by variations of North Atlantic Deep Water Subduction: Paleoceanography

Changes in equatorial Pacific thermocline depth in response to Panamanian seaway closure: Insights from a multi-model study

Abrupt change in atmospheric CO₂ during the last ice age

Nonlinearity of carbon cycle feedbacks

Nitrogen isotope simulations show the importance of atmospheric iron deposition for nitrogen fixation across the Pacific Ocean

What is the skill of ocean tracers in reducing uncertainties about ocean diapycnal mixing and projections of the Atlantic Meridional Overturning Circulation?

Mid-Pliocene shifts in ocean overturning circulation and the onset of Quaternary-style climates

Southern Ocean control of glacial AMOC stability and Dansgaard-Oeschger interstadial duration

Glacial Atlantic overturning increased by wind stress in climate models

Climate Sensitivity Estimated From Temperature Reconstructions of the Last Glacial Maximum

Assessing the effects of ocean diffusivity and climate sensitivity on the rate of global climate change

A review of nitrogen isotopic alteration in marine sediments

Evaluation of Different Methods to Assess Model Projections of the Future Evolution of the Atlantic Meridional Overturning Circulation

Effects of Mountains and Ice Sheets on Global Ocean Circulation

Simulating the global distribution of nitrogen isotopes in the ocean

Glacial greenhouse-gas fluctuations controlled by ocean circulation changes

Using tracer observations to reduce the uncertainty of ocean diapycnal mixing and climate–carbon cycle projections

Limit your search

Academic Affiliation

Creator

Date

Decade

Language

License

Peer Reviewed

Resource Type

Rights Statement

Search Constraints

Search Results

Limit your search