AGW Observer

Observations of anthropogenic global warming

New research – atmospheric and oceanic circulation (October 27, 2016)

Posted by Ari Jokimäki on October 27, 2016

Some of the latest papers on atmospheric and oceanic circulation are shown below. First a few highlighted papers with abstracts and then a list of some other papers. If this subject interests you, be sure to check also the other papers – they are by no means less interesting than the highlighted ones.

Highlights

On the atmospheric response experiment to a Blue Arctic Ocean (Nakamura et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070526/abstract

Abstract: We demonstrated atmospheric responses to a reduction in Arctic sea ice via simulations in which Arctic sea ice decreased stepwise from the present-day range to an ice-free range. In all cases, the tropospheric response exhibited a negative Arctic Oscillation (AO)-like pattern. An intensification of the climatological planetary-scale wave due to the present-day sea ice reduction on the Atlantic side of the Arctic Ocean induced stratospheric polar vortex weakening and the subsequent negative AO. Conversely, strong Arctic warming due to ice-free conditions across the entire Arctic Ocean induced a weakening of the tropospheric westerlies corresponding to a negative AO without troposphere-stratosphere coupling, for which the planetary-scale wave response to a surface heat source extending to the Pacific side of the Arctic Ocean was responsible. Because the resultant negative AO-like response was accompanied by secondary circulation in the meridional plane, atmospheric heat transport into the Arctic increased, accelerating the Arctic amplification.

Atlantic multi-decadal oscillation influence on weather regimes over Europe and the Mediterranean in spring and summer (Zampieri et al. 2016) http://www.sciencedirect.com/science/article/pii/S092181811630371X

Abstract: We analyze the influence of the Atlantic sea surface temperature multi-decadal variability on the day-by-day sequence of large-scale atmospheric circulation patterns (i.e. the “weather regimes”) over the Euro-Atlantic region. In particular, we examine of occurrence of weather regimes from 1871 to present. This analysis is conducted by applying a clustering technique on the daily mean sea level pressure field provided by the 20th Century Reanalysis project, which was successfully applied in other studies focused on the Atlantic Multi-decadal Oscillation (AMO). In spring and summer, results show significant changes in the frequencies of certain weather regimes associated with the phase shifts of the AMO. These changes are consistent with the seasonal surface pressure, precipitation, and temperature anomalies associated with the AMO shifts in Europe.

Ocean and atmosphere feedbacks affecting AMOC hysteresis in a GCM (Jackson et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3336-8

Abstract: Theories suggest that the Atlantic Meridional Overturning Circulation (AMOC) can exhibit a hysteresis where, for a given input of fresh water into the north Atlantic, there are two possible states: one with a strong overturning in the north Atlantic (on) and the other with a reverse Atlantic cell (off). A previous study showed hysteresis of the AMOC for the first time in a coupled general circulation model (Hawkins et al. in Geophys Res Lett. doi:10.1029/2011GL047208, 2011). In this study we show that the hysteresis found by Hawkins et al. (2011) is sensitive to the method with which the fresh water input is compensated. If this compensation is applied throughout the volume of the global ocean, rather than at the surface, the region of hysteresis is narrower and the off states are very different: when the compensation is applied at the surface, a strong Pacific overturning cell and a strong Atlantic reverse cell develops; when the compensation is applied throughout the volume there is little change in the Pacific and only a weak Atlantic reverse cell develops. We investigate the mechanisms behind the transitions between the on and off states in the two experiments, and find that the difference in hysteresis is due to the different off states. We find that the development of the Pacific overturning cell results in greater atmospheric moisture transport into the North Atlantic, and also is likely responsible for a stronger Atlantic reverse cell. These both act to stabilize the off state of the Atlantic overturning.

Arctic amplification: does it impact the polar jet stream? (Meleshko et al. 2016) http://www.tellusa.net/index.php/tellusa/article/view/32330

Abstract: It has been hypothesised that the Arctic amplification of temperature changes causes a decrease in the northward temperature gradient in the troposphere, thereby enhancing the oscillation of planetary waves leading to extreme weather in mid-latitudes. To test this hypothesis, we study the response of the atmosphere to Arctic amplification for a projected summer sea-ice-free period using an atmospheric model with prescribed surface boundary conditions from a state-of-the-art Earth system model. Besides a standard global warming simulation, we also conducted a sensitivity experiment with sea ice and sea surface temperature anomalies in the Arctic. We show that when global climate warms, enhancement of the northward heat transport provides the major contribution to decrease the northward temperature gradient in the polar troposphere in cold seasons, causing more oscillation of the planetary waves. However, while Arctic amplification significantly enhances near-surface air temperature in the polar region, it is not large enough to invoke an increased oscillation of the planetary waves.

Skilful predictions of the winter North Atlantic Oscillation one year ahead (Dunstone et al. 2016) http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo2824.html

Abstract: The winter North Atlantic Oscillation is the primary mode of atmospheric variability in the North Atlantic region and has a profound influence on European and North American winter climate. Until recently, seasonal variability of the North Atlantic Oscillation was thought to be largely driven by chaotic and inherently unpredictable processes. However, latest generation seasonal forecasting systems have demonstrated significant skill in predicting the North Atlantic Oscillation when initialized a month before the onset of winter. Here we extend skilful dynamical model predictions to more than a year ahead. The skill increases greatly with ensemble size due to a spuriously small signal-to-noise ratio in the model, and consequently larger ensembles are projected to further increase the skill in predicting the North Atlantic Oscillation. We identify two sources of skill for second-winter forecasts of the North Atlantic Oscillation: climate variability in the tropical Pacific region and predictable effects of solar forcing on the stratospheric polar vortex strength. We also identify model biases in Arctic sea ice that, if reduced, may further increase skill. Our results open possibilities for a range of new climate services, including for the transport, energy, water management and insurance sectors.

Other papers

Narrowing of the ITCZ in a warming climate: physical mechanisms (Byrne & Schneider, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070396/abstract

Observed and simulated fingerprints of multidecadal climate variability, and their contributions to periods of global SST stagnation (Barcikowska et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0443.1

Observed Changes in the Southern Hemispheric Circulation in May (Ivy et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0394.1

Annual Variations of the Tropopause Height over the Tibetan Plateau Compared with those over other regions (Yang et al. 2016) http://www.sciencedirect.com/science/article/pii/S0377026516300951

The influences of the Atlantic Multidecadal Oscillation on the Mean Strength of the North Pacific Subtropical High during Boreal Winter (Lyu et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0525.1

The Role of Tropical Inter-Basin SST Gradients in Forcing Walker Circulation Trends (Zhang & Karnauskas, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-16-0349.1

The role of low-frequency variation in the manifestation of warming trend and ENSO amplitude (Yeo et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3376-0

Changes in meandering of the Northern Hemisphere circulation (Di Capua & Coumou, 2016) http://iopscience.iop.org/article/10.1088/1748-9326/11/9/094028/meta

Direct observations of the Antarctic Slope Current transport at 113°E (Peña-Molino et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2015JC011594/abstract

Accounting for Centennial Scale Variability when Detecting Changes in ENSO: a study of the Pliocene (Tindall et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016PA002951/abstract

The Quasi-Biennial Oscillation of 2015-16: Hiccup or Death Spiral? (Dunkerton, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070921/abstract

The weakening of the ENSO–Indian Ocean Dipole (IOD) coupling strength in recent decades (Ham et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3339-5

On the Recent Destabilization of the Gulf Stream Path downstream of Cape Hatteras (Andres, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069966/abstract

The relationship between the Madden Julian Oscillation and the North Atlantic Oscillation (Jiang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/qj.2917/abstract

Lessened response of boreal winter stratospheric polar vortex to El Niño in recent decades (Hu et al. 2016) http://rd.springer.com/article/10.1007%2Fs00382-016-3340-z

Warming and weakening trends of the Kuroshio during 1993-2013 (Wang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL069432/abstract

Prolonged El Niño conditions in 2014–15 and the rapid intensification of Hurricane Patricia in the eastern Pacific (Foltz et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070274/abstract

Connection between Anomalous Zonal Activities of the South Asian High and Eurasian Summer Climate Anomalies (Shi & Qian, 2016) http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-15-0823.1

Ranking the strongest ENSO events while incorporating SST uncertainty (Huang et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070888/abstract

The influence of the Gulf Stream on wintertime European blocking (O’Reilly et al. 2016) http://link.springer.com/article/10.1007%2Fs00382-015-2919-0

Projected changes in atmospheric rivers affecting Europe in CMIP5 models (Ramos et al. 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070634/abstract

Hosed vs. unhosed: interruptions of the Atlantic Meridional Overturning Circulation in a global coupled model, with and without freshwater forcing (Brown & Galbraith, 2016) http://www.clim-past.net/12/1663/2016/

An Oceanic Heat Content Based Definition for the Pacific Decadal Oscillation (Kumar & Wen, 2016) http://journals.ametsoc.org/doi/abs/10.1175/MWR-D-16-0080.1

An investigation of the presence of atmospheric rivers over the North Pacific during planetary-scale wave life cycles and their role in Arctic warming (Baggett et al. 2016) http://journals.ametsoc.org/doi/abs/10.1175/JAS-D-16-0033.1

Alternative modelling approaches for the ENSO time series: persistence and seasonality (Gil-Alana, 2016) http://onlinelibrary.wiley.com/doi/10.1002/joc.4850/abstract

Changes in the width of the tropical belt due to simple radiative forcing changes in the GeoMIP simulations (Davis et al. 2016) http://www.atmos-chem-phys.net/16/10083/2016/

Atmospheric River Landfall-Latitude Changes in Future Climate Simulations (Shields & Kiehl, 2016) http://onlinelibrary.wiley.com/doi/10.1002/2016GL070470/abstract

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