16 research outputs found
Interannual variability of sea surface temperature in the eastern tropical Pacific Ocean and Central American rainfall
Sea surface temperature (SST) in the east Pacific warm pool (EPWP) plays a potentially important role in Central American rainfall, tropical cyclogenesis, ocean biology, large-scale tropical heating, and the El Niño-Southern Oscillation (ENSO). The first part of this dissertation is aimed at understanding what processes govern the interannual variability of SST in the EPWP. Interannual wind stress, shortwave radiation, and precipitation were used as forcing to an ocean general circulation model. Shortwave heating was identified as the primary driver of the interannual SST tendency in the EPWP. The high correlation between the EPWP and the equatorial Pacific Ocean is explained by the fact that equatorial SST anomalies modify the distribution of atmospheric vertical motions and therefore cloud cover and shortwave heating. In a parallel set of experiments, the low-frequency variability of the Tehuantepec gap winds was also shown to have a considerable effect on that of SST in the EPWP.
Motivated by the results of the first part of this dissertation, the second part offers significant improvements to the mean state of the equatorial Pacific Ocean in a climatology ocean model experiment by including the Galápagos Islands in the model topography. In this context, the equatorial cold bias is reduced. Furthermore, when the ocean model is coupled to the atmosphere through zonal wind stress, the problem of an excessively regular and biennial ENSO is also reduced. The change in ENSO timescale is a result of the same dynamics operating on a different mean state.
The third part of this dissertation is aimed at understanding the role of the interannual variability of SST in the EPWP in that of Central American rainfall. An anomalously warm EPWP can trigger a rapid enhancement of the east Pacific intertropical convergence zone (ITCZ) in rainy seasons following peak ENSO events, which leads to a rainfall anomaly over Central America. Moreover, the timing and amplitude of the SST-enhanced ITCZ depends on the persistence of the ENSO event. The longer the equatorial SST anomaly persists, the longer the EPWP is subject to anomalous shortwave heating and thus the greater the subsequent SST enhancement of the ITCZ
Recommended from our members
Whither warming in the Galápagos?
The Galápagos Islands play host to an iconic ecosystem—a UNESCO World Heritage Site and the second largest marine reserve in the world, home to several endangered species. The waters off the west coast of the Galápagos are also one of the few places in the world ocean that are presently cooling, with potentially significant ecological consequences of this local reprieve from global warming. Here I show, using a recently developed high-resolution ocean state estimate, that the observed cooling in the Galápagos is the result of a strengthening of the wind-driven equatorial ocean circulation. An acceleration and shift of the Equatorial Undercurrent, which can be attributed to a strengthening of the cross-equatorial component of the trade wind in response to the interhemispheric gradient in surface warming, leads to a 54% increase in upwelling velocity along the western Galápagos Islands as well as increased shear-induced mixing. Analogous to other so-called “cold blobs,” such as the one south of Greenland in the North Atlantic, this is an early and important sentinel of a broader change in the tropical ocean circulation. Thus far, and for perhaps the very near future, the western shores of the Galápagos appear to offer refuge from some of the deleterious impacts of anthropogenic climate change including suppressed upwelling and surface warming. </p
Recommended from our members
Global warming to increase violent crime in the United States
Recent studies have revealed large and robust correlations between seasonal climate and violent crime rates at regional scales within the continental United States, begging the question of how future climate change will influence violent crime rates. Here, we combine empirical models from previous studies with 42 state-of-the-art global climate models to make such projections, while accounting for key factors like regionality and seasonality, and appropriately combining multiple of sources of uncertainty. Our results indicate that the United States should expect an additional 3.2 [2.1–4.5] or 2.3 [1.5–3.2] million violent crimes between 2020 and 2099, depending on greenhouse gas emissions scenario. We also reveal critical dependencies of these violent crime projections on various global warming targets, such as those associated with the Paris Agreement (1.5 °C and 2 °C). These results emphasize the often-overlooked socially-mediated impacts of climate change on human health, with an estimated economic cost of $5 billion annually.
</div
Recommended from our members
Fossil Fuel Combustion Is Driving Indoor CO2 Toward Levels Harmful to Human Cognition
Human activities are elevating atmospheric carbon dioxide concentrations to levels unprecedented in human history. The majority of anticipated impacts of anthropogenic CO2 emissions are mediated by climate warming. Recent experimental studies in the fields of indoor air quality and cognitive psychology and neuroscience, however, have revealed significant direct effects of indoor CO2 levels on cognitive function. Here, we shed light on this connection and estimate the impact of continued fossil fuel emissions on human cognition. We conclude that indoor CO2 levels may indeed reach levels harmful to cognition by the end of this century, and the best way to prevent this hidden consequence of climate change is to reduce fossil fuel emissions. Finally, we offer recommendations for a broad, interdisciplinary approach to improving such understanding and prediction.</p
Recommended from our members
Predicting subsurface sonar observations with satellite-derived ocean surface data in the California Current Ecosystem
Vessel-based sonar systems that focus on the water column provide valuable information on the distribution of underwater marine organisms, but such data are expensive to collect and limited in their spatiotemporal coverage. Satellite data, however, are widely available across large regions and provide information on surface ocean conditions. If satellite data can be linked to subsurface sonar measurements, it may be possible to predict marine life over broader spatial regions with higher frequency using satellite observations. Here, we use random forest models to evaluate the potential for predicting a sonar-derived proxy for subsurface biomass as a function of satellite imagery in the California Current Ecosystem. We find that satellite data may be useful for prediction under some circumstances, but across a range of sonar frequencies and depths, overall model performance was low. Performance in spatial interpolation tasks exceeded performance in spatial and temporal extrapolation, suggesting that this approach is not yet reliable for forecasting or spatial extrapolation. We conclude with some potential limitations and extensions of this work.
</p
Recommended from our members
CMIP5 Zonal Velocity Volumes Near the Equator (3°S–3°N, 160°E–80°W, 0–400 m)
This data set is part of the larger Repeat Observations by Gliders in the Equatorial Region (ROGER) data set available here: https://doi.org/10.25810/pk4z-n050. ROGER was an NSF-funded project from 2012–2016 (OCE–1233282 and OCE–1232971). This page provides access to the data analyzed in the following publication:
Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd (2020) The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, in revision.
As described in the paper, all CMIP3, CMIP5 and CMIP6 global climate model outputs were initially acquired from the Earth System Grid Federation (ESGF). Monthly means from the 1990s were extracted from each model’s historical experiment (labeled “Climate of the Twentieth Century” [20C3M] in CMIP3, and simply “historical” in CMIP5 and CMIP6). A much-reduced and harmonized version of the entire CMIPx ocean zonal velocity (and potential temperature and salinity for CMIP6) output data set was then produced by retaining the time-means of 3D output within the domain 160°E–80°W, 3°S–3°N, 0–400 m and linearly regridding to a common grid (0.25° in longitude, 0.1° in latitude and 1 m in depth). Sections along 93°W were also saved. The resulting analysis sets are provided freely here. Each item provided links to .mat files for each model, which can be downloaded individually or en masse. The cmipx_table.pdf file provided here is necessary to match model numbers with the official CMIPx model identifiers (e.g., C5_M11.mat = CMIP5 / GFDL CM3).
Related publications:
Rudnick, D. L., W. B. Owens, T. M. S. Johnston, K. B. Karnauskas, J. Jakoboski, and R. E. Todd (2020) The equatorial current system during the 2014-2016 El Niño as observed by underwater gliders, J. Phys. Oceanogr., in revision.
Jakoboski, J. K., R. E. Todd, W. B. Owens, K. B. Karnauskas, and D. L. Rudnick, 2020: Bifurcation and Upwelling of the Equatorial Undercurrent West of the Galápagos Archipelago. J. Phys. Oceanogr., 50, 887–905, doi: 10.1175/JPO-D-19-0110.1.</p
Recommended from our members
CMIP3 Zonal Velocity Volumes Near the Equator (3°S–3°N, 160°E–80°W, 0–400 m)
This data set is part of the larger Repeat Observations by Gliders in the Equatorial Region (ROGER) data set available here: https://doi.org/10.25810/pk4z-n050. ROGER was an NSF-funded project from 2012–2016 (OCE–1233282 and OCE–1232971). This page provides access to the data analyzed in the following publication:
Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd (2020) The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, in revision.
As described in the paper, all CMIP3, CMIP5 and CMIP6 global climate model outputs were initially acquired from the Earth System Grid Federation (ESGF). Monthly means from the 1990s were extracted from each model’s historical experiment (labeled “Climate of the Twentieth Century” [20C3M] in CMIP3, and simply “historical” in CMIP5 and CMIP6). A much-reduced and harmonized version of the entire CMIPx ocean zonal velocity (and potential temperature and salinity for CMIP6) output data set was then produced by retaining the time-means of 3D output within the domain 160°E–80°W, 3°S–3°N, 0–400 m and linearly regridding to a common grid (0.25° in longitude, 0.1° in latitude and 1 m in depth). Sections along 93°W were also saved. The resulting analysis sets are provided freely here. Each item provided links to .mat files for each model, which can be downloaded individually or en masse. The cmipx_table.pdf file provided here is necessary to match model numbers with the official CMIPx model identifiers (e.g., C5_M11.mat = CMIP5 / GFDL CM3).
Related publications:
Rudnick, D. L., W. B. Owens, T. M. S. Johnston, K. B. Karnauskas, J. Jakoboski, and R. E. Todd (2020) The equatorial current system during the 2014-2016 El Niño as observed by underwater gliders, J. Phys. Oceanogr., in revision.
Jakoboski, J. K., R. E. Todd, W. B. Owens, K. B. Karnauskas, and D. L. Rudnick, 2020: Bifurcation and Upwelling of the Equatorial Undercurrent West of the Galápagos Archipelago. J. Phys. Oceanogr., 50, 887–905, doi: 10.1175/JPO-D-19-0110.1.</p
Recommended from our members
CMIP6 Salinity Sections Along 93°W (3°S–3°N, 0–500 m)
This data set is part of the larger Repeat Observations by Gliders in the Equatorial Region (ROGER) data set available here: https://doi.org/10.25810/pk4z-n050. ROGER was an NSF-funded project from 2012–2016 (OCE–1233282 and OCE–1232971). This page provides access to the data analyzed in the following publication:
Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd (2020) The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, in revision.
As described in the paper, all CMIP3, CMIP5 and CMIP6 global climate model outputs were initially acquired from the Earth System Grid Federation (ESGF). Monthly means from the 1990s were extracted from each model’s historical experiment (labeled “Climate of the Twentieth Century” [20C3M] in CMIP3, and simply “historical” in CMIP5 and CMIP6). A much-reduced and harmonized version of the entire CMIPx ocean zonal velocity (and potential temperature and salinity for CMIP6) output data set was then produced by retaining the time-means of 3D output within the domain 160°E–80°W, 3°S–3°N, 0–400 m and linearly regridding to a common grid (0.25° in longitude, 0.1° in latitude and 1 m in depth). Sections along 93°W were also saved. The resulting analysis sets are provided freely here. Each item provided links to .mat files for each model, which can be downloaded individually or en masse. The cmipx_table.pdf file provided here is necessary to match model numbers with the official CMIPx model identifiers (e.g., C5_M11.mat = CMIP5 / GFDL CM3).
Related publications:
Rudnick, D. L., W. B. Owens, T. M. S. Johnston, K. B. Karnauskas, J. Jakoboski, and R. E. Todd (2020) The equatorial current system during the 2014-2016 El Niño as observed by underwater gliders, J. Phys. Oceanogr., in revision.
Jakoboski, J. K., R. E. Todd, W. B. Owens, K. B. Karnauskas, and D. L. Rudnick, 2020: Bifurcation and Upwelling of the Equatorial Undercurrent West of the Galápagos Archipelago. J. Phys. Oceanogr., 50, 887–905, doi: 10.1175/JPO-D-19-0110.1.</p
Recommended from our members
CMIP3 Zonal Velocity Sections Along 93°W (3°S–3°N, 0–500 m)
This data set is part of the larger Repeat Observations by Gliders in the Equatorial Region (ROGER) data set available here: https://doi.org/10.25810/pk4z-n050. ROGER was an NSF-funded project from 2012–2016 (OCE–1233282 and OCE–1232971). This page provides access to the data analyzed in the following publication:
Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd (2020) The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, in revision.
As described in the paper, all CMIP3, CMIP5 and CMIP6 global climate model outputs were initially acquired from the Earth System Grid Federation (ESGF). Monthly means from the 1990s were extracted from each model’s historical experiment (labeled “Climate of the Twentieth Century” [20C3M] in CMIP3, and simply “historical” in CMIP5 and CMIP6). A much-reduced and harmonized version of the entire CMIPx ocean zonal velocity (and potential temperature and salinity for CMIP6) output data set was then produced by retaining the time-means of 3D output within the domain 160°E–80°W, 3°S–3°N, 0–400 m and linearly regridding to a common grid (0.25° in longitude, 0.1° in latitude and 1 m in depth). Sections along 93°W were also saved. The resulting analysis sets are provided freely here. Each item provided links to .mat files for each model, which can be downloaded individually or en masse. The cmipx_table.pdf file provided here is necessary to match model numbers with the official CMIPx model identifiers (e.g., C5_M11.mat = CMIP5 / GFDL CM3).
Related publications:
Rudnick, D. L., W. B. Owens, T. M. S. Johnston, K. B. Karnauskas, J. Jakoboski, and R. E. Todd (2020) The equatorial current system during the 2014-2016 El Niño as observed by underwater gliders, J. Phys. Oceanogr., in revision.
Jakoboski, J. K., R. E. Todd, W. B. Owens, K. B. Karnauskas, and D. L. Rudnick, 2020: Bifurcation and Upwelling of the Equatorial Undercurrent West of the Galápagos Archipelago. J. Phys. Oceanogr., 50, 887–905, doi: 10.1175/JPO-D-19-0110.1.</p
Recommended from our members
CMIP6 Zonal Velocity Volumes Near the Equator (3°S–3°N, 160°E–80°W, 0–400 m)
This data set is part of the larger Repeat Observations by Gliders in the Equatorial Region (ROGER) data set available here: https://doi.org/10.25810/pk4z-n050. ROGER was an NSF-funded project from 2012–2016 (OCE–1233282 and OCE–1232971). This page provides access to the data analyzed in the following publication:
Karnauskas, K. B., J. Jakoboski, T. M. S. Johnston, W. B. Owens, D. L. Rudnick, and R. E. Todd (2020) The Pacific Equatorial Undercurrent in Three Generations of Global Climate Models and Glider Observations. J. Geophys. Res.–Oceans, in revision.
As described in the paper, all CMIP3, CMIP5 and CMIP6 global climate model outputs were initially acquired from the Earth System Grid Federation (ESGF). Monthly means from the 1990s were extracted from each model’s historical experiment (labeled “Climate of the Twentieth Century” [20C3M] in CMIP3, and simply “historical” in CMIP5 and CMIP6). A much-reduced and harmonized version of the entire CMIPx ocean zonal velocity (and potential temperature and salinity for CMIP6) output data set was then produced by retaining the time-means of 3D output within the domain 160°E–80°W, 3°S–3°N, 0–400 m and linearly regridding to a common grid (0.25° in longitude, 0.1° in latitude and 1 m in depth). Sections along 93°W were also saved. The resulting analysis sets are provided freely here. Each item provided links to .mat files for each model, which can be downloaded individually or en masse. The cmipx_table.pdf file provided here is necessary to match model numbers with the official CMIPx model identifiers (e.g., C5_M11.mat = CMIP5 / GFDL CM3).
Related publications:
Rudnick, D. L., W. B. Owens, T. M. S. Johnston, K. B. Karnauskas, J. Jakoboski, and R. E. Todd (2020) The equatorial current system during the 2014-2016 El Niño as observed by underwater gliders, J. Phys. Oceanogr., in revision.
Jakoboski, J. K., R. E. Todd, W. B. Owens, K. B. Karnauskas, and D. L. Rudnick, 2020: Bifurcation and Upwelling of the Equatorial Undercurrent West of the Galápagos Archipelago. J. Phys. Oceanogr., 50, 887–905, doi: 10.1175/JPO-D-19-0110.1.</p