A Multidecadal-Scale Tropically Driven Global Teleconnection over the Past Millennium and Its Recent Strengthening (original) (raw)
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Atmosphere, 2016
In this paper, the teleconnections from the tropical Atlantic to the Indo-Pacific region from inter-annual to centennial time scales will be reviewed. Identified teleconnections and hypotheses on mechanisms at work are reviewed and further explored in a century-long pacemaker coupled ocean-atmosphere simulation ensemble. There is a substantial impact of the tropical Atlantic on the Pacific region at inter-annual time scales. An Atlantic Niño (Niña) event leads to rising (sinking) motion in the Atlantic region, which is compensated by sinking (rising) motion in the central-western Pacific. The sinking (rising) motion in the central-western Pacific induces easterly (westerly) surface wind anomalies just to the west, which alter the thermocline. These perturbations propagate eastward as upwelling (downwelling) Kelvin-waves, where they increase the probability for a La Niña (El Niño) event. Moreover, tropical North Atlantic sea surface temperature anomalies are also able to lead La Niña/El Niño development. At multidecadal time scales, a positive (negative) Atlantic Multidecadal Oscillation leads to a cooling (warming) of the eastern Pacific and a warming (cooling) of the western Pacific and Indian Ocean regions. The physical mechanism for this impact is similar to that at inter-annual time scales. At centennial time scales, the Atlantic warming induces a substantial reduction of the eastern Pacific warming even under CO2 increase and to a strong subsurface cooling.
Journal of Climate
A 1000-yr control simulation in a low-resolution coupled atmosphere–ocean model from the Geophysical Fluid Dynamics Laboratory (GFDL) family of climate models shows a natural, highly regular multidecadal oscillation between periods of Southern Ocean (SO) open-ocean convection and nonconvective periods. It is shown here that convective periods are associated with warming of the SO sea surface temperatures (SSTs), and more broadly of the Southern Hemisphere (SH) SSTs and atmospheric temperatures. This SO warming results in a decrease in the meridional gradient of SSTs in the SH, changing the large-scale pressure patterns, reducing the midlatitude baroclinicity and thus the magnitude of the southern Ferrel and Hadley cells, and weakening the SO westerly winds and the SH tropical trade winds. The rearrangement of the atmospheric circulation is consistent with the global energy balance. During convective decades, the increase in incoming top-of-the-atmosphere radiation in the SH is balan...
ENSO–Rainfall Teleconnection over the Maritime Continent Enhances and Shifts Eastward under Warming
Journal of Climate
The Maritime Continent (MC), located in the heart of the Indo-Pacific warm pool, plays an important role in the global climate. However, the future MC climate is largely unknown, in particular the ENSO–rainfall teleconnection. ENSO induces a zonal dipole pattern of rainfall variability across the Indo-Pacific Ocean, that is, positive variability in the tropical Pacific and negative variability toward the MC. Here, new CMIP6 models robustly project that, for both land and sea rainfall, the negative ENSO teleconnection over the MC (drier during El Niño and wetter during La Niña) could intensify significantly under the Shared Socioeconomic Pathway 5–8.5 (SSP585) warming scenario. A strengthened teleconnection may cause enhanced droughts and flooding, leading to agricultural impacts and altering rainfall predictability over the region. Models also project that both the Indo-Pacific rainfall center and the zero crossing of dipole-like rainfall variability shift eastward; these adjustment...
Pacific Influences on Tropical Atlantic Teleconnections to the Southern Hemisphere High Latitudes
Journal of Climate, 2016
Several recent studies have connected Antarctic climate variability to tropical Atlantic sea surface temperatures (SST), proposing a Rossby wave response from the Atlantic as the primary dynamical mechanism. In this investigation, reanalysis data and atmospheric general circulation model experiments are used to further diagnose these dynamical links. Focus is placed on the possible mediating role of Pacific processes, motivated by the similar spatial characteristics of Southern Hemisphere (SH) teleconnections associated with tropical Atlantic and Pacific SST variability. During austral winter (JJA), both reanalyses and model simulations reveal that Atlantic teleconnections represent a two-mechanism process, whereby increased tropical Atlantic SST promotes two conditions: 1) an intensification of the local Atlantic Hadley circulation (HC), driven by enhanced interaction between SST anomalies and the ITCZ, that increases convergence at the descending branch, establishing anomalous vor...
Climate Dynamics, 2018
Decadal changes in the teleconnection between the central tropical Pacific and the Southern Hemisphere extratropics are studied using the NCEP-NCAR reanalysis data. Concurrent and lagged relationships show that teleconnection strength in austral spring was weak (strong) before (after) 1996/1997. This decadal change coincides in time with the climate regime shift in the Pacific in the 1990s known from many studies. We show that, after the regime shift, the concurrent and delayed teleconnection with the Southern Hemisphere extratropics is insignificant in September and abruptly increases in October. Penetration of the stratospheric anomaly into the troposphere in October can indicate interacting tropospheric and stratospheric pathways of the teleconnection to strongly enhance the central tropical Pacific impact since the late 1990s. The results give evidence that the Southern Annular Mode seems to be connecting element between the two pathways in the recent decades. The common tendencies in the eastward shift of the tropical anomalies and zonal wave 1 phase in the Antarctic stratosphere in austral spring have been demonstrated. The difference between the central Pacific and eastern Pacific teleconnections is consistent with that known from previous studies and new tendencies in their decadal changes and delayed effects have been revealed. It has been found that the central Pacific contributions to the Pacific decadal oscillation and to the Northern Hemisphere stratosphere have also increased significantly after the 1990s. This characterizes the central tropical Pacific as one of the key regions impacting climate and teleconnection not only in the Southern Hemisphere, but also in the Northern Hemisphere. Our findings are consistent with and further develop the recent studies of the stratosphere-troposphere coupling in austral spring, and emphasize significant contribution of the delayed tropical signals to the climate variability in austral spring in both hemispheres.
The dominant interannual El Niiio-Southern Oscillation phenomenon (ENSO) and the short length of climate observation records make it difficult to study long-term climate variations in the spatiotemporal domain. Based on the fact that the ENS0 signal spreads to remote regions and induces delayed climate variation through atmospheric teleconnections, we develop an ENSO-removal method through which the ENS0 signal can be approximately removed at the grid box level from the spatiotemporal field of a climate parameter. After this signal is removed, long-term climate variations are isolated at middle and low latitudes in the climate parameter fields from observed and reanalysis datasets. This paper addresses the long-term global warming trend (GW); a companion paper concentrates on Pacific pan-decadal variability (PDV).The warming that occurs in the Pacific basin (approximately 0.4K in the 2oth century) is much weaker than in surrounding regions and the other two ocean basins (approximately 0.8K). The modest warming in the Pacific basin is likely due to its dynamic nature on the interannual and decadal time scales and/or the leakage of upper ocean water through the Indonesian Throughflow. Based on the NCEPNCAR and ERA-40 reanalyses, a comprehensive atmospheric structure associated with the GW trend is given. Significant discrepancies exist between the two datasets, especially in the tightly coupled dynamics and water vapor fields. The dynamics fields based on NCEPNCAR, which show a change in the Walker Circulation, are consistent with the GW change in the surface temperature field. However, intensification in the Hadley Circulation is associated with GW trend in ERA-40 instead.
Potential tropical Atlantic impacts on Pacific decadal climate trends
Geophysical Research Letters, 2016
The tropical Pacific cooling from the early 1990s to 2013 has contributed to the slowdown of globally averaged sea surface temperatures (SSTs). The origin of this regional cooling trend still remains elusive. Here we demonstrate that the remote impact of Atlantic SST anomalies, as well as local atmosphere-ocean interactions, contributed to the eastern Pacific cooling during this period. By assimilating observed three-dimensional Atlantic temperature and salinity anomalies into a coupled general circulation model, we are able to qualitatively reproduce the observed Pacific decadal trends of SST and sea level pressure (SLP), albeit with reduced amplitude. Although a major part of the Pacific SLP trend can be explained by equatorial Pacific SST forcing only, the origin of this low-frequency variability can be traced back further to the remote impacts of equatorial Atlantic and South Atlantic SST trends. Atlantic SST impacts on the atmospheric circulation can also be detected for the Northeastern Pacific, thus providing a linkage between Atlantic climate and Western North American drought conditions.
Unprecedented recent warming of surface temperatures in the eastern tropical Pacific Ocean
Nature …, 2008
Oscillation system, climate variability in the tropical Pacific Ocean influences climate across much of the planet. But the history of temperature change in the tropical Pacific Ocean during recent millennia is poorly known: the available annually resolved records 1,2 are discontinuous and rarely span more than a few centuries. Longer records at coarser temporal resolution suggest that significant oceanographic changes, observed at multi-year to multi-century resolution, have had important effects on global climate 3-5 . Here we use a diatom record from El Junco Lake, Galápagos, to produce a calibrated, continuous record of sea surface temperature in the eastern tropical Pacific Ocean at subdecadal resolution, spanning the past 1,200 years. Our reconstruction reveals that the most recent 50 years are the warmest 50-year period within the record. Because our diatom-based sea surface temperature index resembles Northern Hemisphere temperature reconstructions, we suggest that with continued anthropogenic warming, the eastern tropical Pacific Ocean may continue to warm.
Atmospheric bridge, oceanic tunnel, and global climatic teleconnections
REVIEWS OF GEOPHYSICS-RICHMOND VIRGINIA …, 2007
We review teleconnections within the atmosphere and ocean, their dynamics and their role in coupled climate variability. We concentrate on teleconnections in the latitudinal direction, notably tropical-extratropical and interhemispheric interactions, and discuss the timescales of several teleconnection processes. The tropical impact on extratropical climate is accomplished mainly through the atmosphere. In particular, tropical Pacific sea surface temperature anomalies impact extratropical climate variability through stationary atmospheric waves and their interactions with midlatitude storm tracks. Changes in the extratropics can also impact the tropical climate through upper ocean subtropical cells at decadal and longer timescales. On the global scale the tropics and subtropics interact through the atmospheric Hadley circulation and the oceanic subtropical cell. The thermohaline circulation can provide an effective oceanic teleconnection for interhemispheric climate interactions.