Article
Meteorology & Atmospheric Sciences
David B. Bonan, Andrew F. Thompson, Emily R. Newsom, Shantong Sun, Maria Rugenstein
Summary: This study examines the response of the Atlantic meridional overturning circulation (AMOC) to an abrupt quadrupling of atmospheric carbon dioxide using a collection of GCM simulations. The simulations show consistent weakening of the AMOC during the first century, but diverse behaviors over longer time scales. The study attributes the AMOC behavior to changes in temperature and salinity in different regions, highlighting the importance of considering high-latitude freshwater changes and salinity anomalies for understanding the long-term evolution of the AMOC.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Yang Li, Haijun Yang
Summary: This study uses a single-hemisphere 4-box model to investigate the low-frequency variability of the Atlantic meridional overturning circulation (AMOC). It suggests that the AMOC exhibits a self-sustained multicentennial oscillation when an enhanced mixing mechanism is introduced in the subpolar ocean. The study also shows that stochastic freshwater forcing can excite the multicentennial oscillation. These findings suggest the presence of an intrinsic multicentennial mode in the Atlantic Ocean.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Yuan-Jen Lin, Briane. J. Rose, Yen -Ting Hwang
Summary: While most models agree that the Atlantic meridional overturning circulation (AMOC) becomes weaker under greenhouse gas emission and is likely to weaken over the twenty-first century, they disagree on the projected magnitudes of AMOC weakening. CMIP6 models with stronger climatological AMOC are shown to project stronger AMOC weakening in both 1% ramping CO2 and abrupt CO2 quadrupling simulations. This is because models with stronger mean state AMOC exhibit weaker stratification in the upper Labrador Sea, allowing for stronger mixing of the surface buoyancy flux and leading to subsurface warming and AMOC weakening.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Anastasia Romanou, David Rind, Jeff Jonas, Ron Miller, Maxwell Kelley, Gary Russell, Clara Orbe, Larissa Nazarenko, Rebecca Latto, Gavin a. Schmidt
Summary: A 10-member ensemble simulation with the NASA GISS-E2-1-G climate model shows a clear bifurcation in the Atlantic meridional overturning circulation (AMOC) strength under the SSP2-4.5 extended scenario. This response is a manifestation of noise-induced bifurcation, enhanced by feedbacks, revealing the role stochastic variability may play in AMOC stability. Rating: 7/10.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Anne-Sophie Fortin, Carolina O. Dufour, Timothy M. Merlis, Rym Msadek
Summary: This study investigates the response of the Atlantic meridional overturning circulation (AMOC) to increased atmospheric carbon dioxide (CO2) concentration and identifies the drivers of this response. The research finds that different representations of oceanic processes lead to significant differences in the AMOC response across climate models. The AMOC shows a reduction of similar magnitude in low and high resolutions, while a muted response is found in medium resolution. Changes in the geostrophic and eddy streamfunctions contribute differently to the AMOC decline and there is a weak connection between the deep water formation regions and the Deep Western Boundary Current in the medium resolution.
JOURNAL OF CLIMATE
(2023)
Article
Oceanography
Xiaoting Yang, Paola Cessi
Summary: Multidecadal variability has been observed in the time series of North Atlantic SST, and various mechanisms have been proposed to explain it. The role of the Arctic Ocean, especially the freshwater flux from Bering Strait, has been underappreciated. This study uses idealized configurations to investigate the role of Bering Strait in the multidecadal variability and finds that its freshwater transport enhances the local density gradient and contributes to the instability and emergence of large-scale anomalies.
JOURNAL OF PHYSICAL OCEANOGRAPHY
(2023)
Article
Meteorology & Atmospheric Sciences
Clara Orbe, David Rind, Ron l. Miller, Larissa S. Nazarenko, Anastasia Romanou, Jeffrey Jonas, Gary l. Russell, Maxwell Kelley, Gavin A. Schmidt
Summary: Climate models project a future weakening of the AMOC, but the impacts of this on climate are uncertain. By using a unique ensemble of CMIP6 GISS ModelE (E2.1) SSP 2-4.5 integrations, we isolate the climate impacts of a weakened AMOC and find that it results in a northward shift and strengthening of the NH Hadley cell and intensification of the northern midlatitude eddy-driven jet.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Rui Jiang, Haijun Yang
Summary: The study found that the Rocky Mountains have a significant impact on atmospheric moisture transport between the Atlantic and Pacific Oceans, but play a trivial role in Northern Hemisphere deep-water formation.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Hyo-Jeong Kim, Soon-Il An, Soong-Ki Kim, Jae-Heung Park
Summary: This study aims to improve the understanding of transient thermohaline circulation responses under rapidly varying forcing and their dependence on forcing time scales. The results suggest that the Atlantic meridional overturning circulation collapse and recovery occur at higher and lower freshwater forcing values, respectively, when the forcing time scale is shorter.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Dafydd Stephenson, F. Sevellec
Summary: This study introduces an optimization framework and computational method to investigate sources of ocean uncertainty, revealing that high-frequency variations in meridional transports are mainly wind-driven, while surface buoyancy forcing is the dominant source of uncertainty at lower frequencies. Mesoscale eddies contribute the most to year-averaged quantities in the subtropical region, but their impact is significantly reduced in the subpolar region.
JOURNAL OF CLIMATE
(2021)
Article
Meteorology & Atmospheric Sciences
Shantong Sun, Andrew F. Thompson, Shang-Ping Xie, Shang-Min Long
Summary: The reorganization of the Atlantic meridional overturning circulation (AMOC) leads to interbasin heat transport, which redistributes heat between the Atlantic and Indo-Pacific basins. This transient response plays a key role in the global ocean heat budget, especially in a changing climate.
JOURNAL OF CLIMATE
(2022)
Article
Multidisciplinary Sciences
Sara Berglund, Kristofer Doos, Sjoerd Groeskamp, Trevor J. McDougall
Summary: The Atlantic Meridional Overturning Circulation (AMOC) is crucial for regulating Earth's climate, and a new feature related to the northward flowing component of AMOC within the North Atlantic Subtropical Gyre has been identified. It has been found that 70% of the northward flowing water in AMOC circulates within the Gyre before continuing its northward path. This circulation is important for increasing density and depth, which in turn affect the strength and variability of AMOC and heat transport towards the north.
NATURE COMMUNICATIONS
(2022)
Article
Multidisciplinary Sciences
Jiechun Deng, Aiguo Dai
Summary: The study shows that sea ice-air interactions are crucial for multidecadal climate variability in both the Arctic and North Atlantic. By amplifying multidecadal variations in sea-ice cover, sea surface temperatures, and surface air temperature, sea ice-air interactions mainly affect the Atlantic Meridional Overturning Circulation through changes in surface fluxes.
NATURE COMMUNICATIONS
(2022)
Article
Meteorology & Atmospheric Sciences
Oliver J. Tooth, Helen L. Johnson, Chris Wilson
Summary: The strength of the AMOC at subpolar latitudes is dominated by water mass transformation in the eastern SPNA. However, the distribution of this overturning across the individual circulation pathways of both the SPG and the Nordic seas overflows is poorly understood. Water mass transformation along the pathways of the eastern SPG accounts for 55% of the mean strength of the eastern subpolar AMOC.
JOURNAL OF CLIMATE
(2023)
Article
Meteorology & Atmospheric Sciences
Bryam Orihuela-Pinto, Agus Santoso, Matthew H. England, Andrea S. Taschetto
Summary: This study investigates the effect of an AMOC collapse on ENSO by adding freshwater in the North Atlantic in a global climate model. The results show that an AMOC collapse leads to weaker ENSO variability, with a reduction in extreme El Nino events and a shift of the ENSO pattern toward the central Pacific.
JOURNAL OF CLIMATE
(2022)
Article
Environmental Sciences
Ilona Mettiainen, Holly Jean Buck, Douglas G. MacMartin, Katharine L. Ricke
Summary: This study examines the importance and rationale of public engagement in solar geoengineering research, specifically focusing on the perspective of Arctic communities. The findings suggest that public engagement can generate better knowledge, contribute to scientific research, and act as a de facto form of governance in the absence of formal governance.
ENVIRONMENTAL RESEARCH LETTERS
(2022)
Article
Meteorology & Atmospheric Sciences
Emily Newsom, Laure Zanna, Samar Khatiwala
Summary: This study aims to better understand the geographic pattern of ocean warming caused by human-driven climate change. The research finds that ocean warming patterns are influenced by both the ocean's heat absorption and changes in ocean currents, which are interconnected processes. Changes in ocean currents reduce regional variations in the build-up of new heat absorbed from the atmosphere. This finding is significant for predicting regional ocean warming and its impacts.
JOURNAL OF CLIMATE
(2022)
Article
Meteorology & Atmospheric Sciences
Matthew P. Couldrey, Jonathan M. Gregory, Xiao Dong, Oluwayemi Garuba, Helmuth Haak, Aixue Hu, William J. Hurlin, Jiangbo Jin, Johann Jungclaus, Armin Koehl, Hailong Liu, Sayantani Ojha, Oleg A. Saenko, Abhishek Savita, Tatsuo Suzuki, Zipeng Yu, Laure Zanna
Summary: The effect of anthropogenic climate change in the ocean is challenging to project due to the different responses of atmosphere-ocean general circulation models (AOGCMs). This study focuses on the changes in the Atlantic Meridional Overturning Circulation (AMOC), ocean heat content (Delta OHC), and the spatial pattern of ocean dynamic sea level (Delta zeta). The results show that the weakening of AMOC is mainly caused by the North Atlantic heat flux perturbation, and further weakened by a positive coupled heat flux feedback. The AMOC decline has significant impacts on the warming of the South Atlantic-Southern Ocean interface.
Article
Geosciences, Multidisciplinary
Ewa M. Bednarz, Daniele Visioni, Antara Banerjee, Peter Braesicke, Ben Kravitz, Douglas G. MacMartin
Summary: Modeling experiments reducing solar constant can lower surface temperatures, but they also induce other stratospheric dynamical responses that have important impacts on southern hemisphere surface climate.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Multidisciplinary Sciences
D. G. MacMartin, D. Visioni, B. Kravitz, J. H. Richter, T. Felgenhauer, W. R. Lee, D. R. Morrow, E. A. Parson, M. Sugiyama
Summary: Making informed decisions about solar radiation modification requires projections of climate response and impacts. Current simulations only consider a single scenario, limiting the ability to compare risks. To address this, this study presents a range of scenarios and simulations for broad community use.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Meteorology & Atmospheric Sciences
Elizabeth Yankovsky, Laure Zanna, K. Shafer Smith
Summary: Understanding the impact of eddies on flow structure is essential for climate models. This study investigates the influence of eddies on vertical structure as a function of resolution and dynamical regime. It examines the distribution of potential and kinetic energy and finds that increasing resolution leads to higher kinetic energy and lower potential energy, with the dominant trend being an increased fraction of kinetic energy going into the barotropic mode as eddies are better resolved. The study also explores how the underlying dynamical regime affects energetic pathways.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2022)
Article
Meteorology & Atmospheric Sciences
Andrew Ross, Ziwei Li, Pavel Perezhogin, Carlos Fernandez-Granda, Laure Zanna
Summary: Recently, there has been an increasing use of machine learning models in parameterizing computationally intensive subgrid-scale processes in ocean models. In this study, the online performance, generalization capabilities, and sensitivity to data set design choices of these models were systematically evaluated. The choice of filtering and coarse-graining operator was found to be critical, and should be guided by the specific application. Additionally, a novel equation-discovery approach combining linear regression and genetic programming with spatial derivatives was proposed to improve generalization and interpretability.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2023)
Article
Geosciences, Multidisciplinary
Walker R. R. Lee, Daniele Visioni, Ewa M. M. Bednarz, Douglas G. G. MacMartin, Ben Kravitz, Simone Tilmes
Summary: In this study, two simulations of stratospheric aerosol injection (SAI) at different altitudes were compared. It was found that lower-altitude SAI requires 64% more injection to achieve the same cooling effect. SAI at higher altitudes cools the surface more efficiently due to longer lifetimes of SO2 and SO4 and the water vapor feedback mechanism.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Meteorology & Atmospheric Sciences
Aakash Sane, Brandon G. Reichl, Alistair Adcroft, Laure Zanna
Summary: In this study, we improved a parameterization of vertical mixing in the ocean surface boundary layer by enhancing its eddy diffusivity model using data-driven methods, specifically neural networks. The improved scheme outperforms its predecessor by reducing biases in the mixed-layer depth and upper ocean stratification, demonstrating the potential for data-driven physics-aware parameterizations to improve global climate models.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2023)
Article
Meteorology & Atmospheric Sciences
Cheng Zhang, Pavel Perezhogin, Cem Gultekin, Alistair Adcroft, Carlos Fernandez-Granda, Laure Zanna
Summary: This study addresses how to use machine learned parameterization in a general circulation model and evaluates its performance. The researchers found the parameterization to be stable but identified some limitations in its implementation, suggesting further refinement may be needed.
JOURNAL OF ADVANCES IN MODELING EARTH SYSTEMS
(2023)
Article
Environmental Sciences
D. Visioni, E. M. Bednarz, D. G. Macmartin, B. Kravitz, P. B. Goddard
Summary: The specifics of simulated injection choices in stratospheric aerosol injections (SAI) are crucial for understanding the impacts of SAI on the planet. Different amounts of cooling can be achieved through SAI simulations, and the choice of baseline period is important for comparing these responses. This study explores the relationship between cooling achieved and various surface impacts, and highlights the significance of the baseline period in policy discussions.
Article
Environmental Sciences
Douglas G. Macmartin, Ben Kravitz, Paul B. Goddard
Summary: Regional geoengineering is a means to target specific regional impacts of climate change by reflecting sunlight over a limited spatial domain. Concerns have been raised about the detectable effects of such approaches beyond the targeted region. A few studies have found that when applied to relatively small domains, these approaches only have limited effects on adjacent regions, suggesting the need for distinct governance compared to global sunlight reflection.
ENVIRONMENTAL RESEARCH COMMUNICATIONS
(2023)
Article
Environmental Sciences
Ewa M. Bednarz, Daniele Visioni, Ben Kravitz, Andy Jones, James M. Haywood, Jadwiga Richter, Douglas G. MacMartin, Peter Braesicke
Summary: This paper presents a comparison of three state-of-the-art Earth system models to study the atmospheric responses to stratospheric aerosol injection (SAI) at various latitudes in the tropics. The study reveals the role of biases in circulation and model microphysics in driving the differences in simulated sulfate distributions. The results contribute to understanding the physical mechanisms and reducing uncertainty in model projections of climate impacts from SAI.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2023)
Article
Environmental Sciences
Daniele Visioni, Ewa M. Bednarz, Walker R. Lee, Ben Kravitz, Andy Jones, Jim M. Haywood, Douglas G. MacMartin
Summary: This study presents the results of a systematic intercomparison of climate responses in three Earth system models regarding the injection of SO2 in the lower stratosphere. The goal is to determine commonalities and differences in the distribution of sulfate aerosols and surface response to reduction in solar radiation. The study highlights the potential for designing comprehensive intervention strategies using these simulations.
ATMOSPHERIC CHEMISTRY AND PHYSICS
(2023)
Article
Geosciences, Multidisciplinary
Yan Zhang, Douglas G. MacMartin, Daniele Visioni, Ben Kravitz
Summary: Stratospheric aerosol injection (SAI) has the potential to reduce the risks of climate change by temporarily cooling the global climate. The choices of injection latitude(s) and season(s) can lead to significant differences in regional surface climate, and there are at least three degrees of freedom (DOFs) that can be used to manage different climate goals. Quantifying the number of meaningful independent DOFs in the SAI design space reveals that there are likely between six and eight DOFs for a cooling level of 1-1.5 degrees C.
EARTH SYSTEM DYNAMICS
(2022)