An Interdecadal Shift of the Extratropical Teleconnection From the Tropical Pacific During Boreal Summer

Christopher H. O'Reilly; Tim Woollings; Laure Zanna; Antje Weisheimer

doi:10.1029/2019gl084079

Impacts of the Tropical Pacific–Indian Ocean Associated Mode on Madden–Julian Oscillation over the Maritime Continent in Boreal Winter

Atmosphere ◽

10.3390/atmos11101049 ◽

2020 ◽

Vol 11 (10) ◽

pp. 1049

Author(s):

Xin Li ◽

Ming Yin ◽

Xiong Chen ◽

Minghao Yang ◽

Fei Xia ◽

...

Keyword(s):

Indian Ocean ◽

Kinetic Energy ◽

Tropical Pacific ◽

Western Pacific ◽

Boreal Summer ◽

Boreal Winter ◽

Madden Julian Oscillation ◽

Maritime Continent ◽

The Western Pacific ◽

The Tropical Pacific

Based on the observation and reanalysis data, the relationship between the Madden–Julian Oscillation (MJO) over the Maritime Continent (MC) and the tropical Pacific–Indian Ocean associated mode was analyzed. The results showed that the MJO over the MC region (95°–150° E, 10° S–10° N) (referred to as the MC–MJO) possesses prominent interannual and interdecadal variations and seasonally “phase-locked” features. MC–MJO is strongest in the boreal winter and weakest in the boreal summer. Winter MC–MJO kinetic energy variation has significant relationships with the El Niño–Southern Oscillation (ENSO) in winter and the Indian Ocean Dipole (IOD) in autumn, but it correlates better with the tropical Pacific–Indian Ocean associated mode (PIOAM). The correlation coefficient between the winter MC–MJO kinetic energy index and the autumn PIOAM index is as high as −0.5. This means that when the positive (negative) autumn PIOAM anomaly strengthens, the MJO kinetic energy over the winter MC region weakens (strengthens). However, the correlation between the MC–MJO convection and PIOAM in winter is significantly weaker. The propagation of MJO over the Maritime Continent differs significantly in the contrast phases of PIOAM. During the positive phase of the PIOAM, the eastward propagation of the winter MJO kinetic energy always fails to move across the MC region and cannot enter the western Pacific. However, during the negative phase of the PIOAM, the anomalies of MJO kinetic energy over the MC is not significantly weakened, and MJO can propagate farther eastward and enter the western Pacific. It should be noted that MJO convection is more likely to extend to the western Pacific in the positive phases of PIOAM than in the negative phases. This is significant different with the propagation of the MJO kinetic energy.

Strengthening of the Pacific Equatorial Undercurrent in the SODA Reanalysis: Mechanisms, Ocean Dynamics, and Implications

Journal of Climate ◽

10.1175/jcli-d-13-00359.1 ◽

2014 ◽

Vol 27 (6) ◽

pp. 2405-2416 ◽

Cited By ~ 30

Author(s):

Elizabeth J. Drenkard ◽

Kristopher B. Karnauskas

Keyword(s):

Heat Budget ◽

Tropical Pacific ◽

Global Climate Models ◽

Ocean Dynamics ◽

Eastern Pacific ◽

Boreal Summer ◽

Trade Winds ◽

Equatorial Undercurrent ◽

The Pacific ◽

The Tropical Pacific

Abstract Several recent studies utilizing global climate models predict that the Pacific Equatorial Undercurrent (EUC) will strengthen over the twenty-first century. Here, historical changes in the tropical Pacific are investigated using the Simple Ocean Data Assimilation (SODA) reanalysis toward understanding the dynamics and mechanisms that may dictate such a change. Although SODA does not assimilate velocity observations, the seasonal-to-interannual variability of the EUC estimated by SODA corresponds well with moored observations over a ~20-yr common period. Long-term trends in SODA indicate that the EUC core velocity has increased by 16% century−1 and as much as 47% century−1 at fixed locations since the mid-1800s. Diagnosis of the zonal momentum budget in the equatorial Pacific reveals two distinct seasonal mechanisms that explain the EUC strengthening. The first is characterized by strengthening of the western Pacific trade winds and hence oceanic zonal pressure gradient during boreal spring. The second entails weakening of eastern Pacific trade winds during boreal summer, which weakens the surface current and reduces EUC deceleration through vertical friction. EUC strengthening has important ecological implications as upwelling affects the thermal and biogeochemical environment. Furthermore, given the potential large-scale influence of EUC strength and depth on the heat budget in the eastern Pacific, the seasonal strengthening of the EUC may help reconcile paradoxical observations of Walker circulation slowdown and zonal SST gradient strengthening. Such a process would represent a new dynamical “thermostat” on CO2-forced warming of the tropical Pacific Ocean, emphasizing the importance of ocean dynamics and seasonality in understanding climate change projections.

Evaluating the performance of CMIP6 models in the tropical Atlantic: mean state, variability, and remote impacts

10.5194/egusphere-egu2020-12722 ◽

2020 ◽

Author(s):

Ingo Richter ◽

Hiroki Tokinaga

Keyword(s):

General Circulation ◽

General Circulation Models ◽

Tropical Pacific ◽

Boreal Summer ◽

Tropical Atlantic ◽

Westerly Wind ◽

Equatorial Atlantic ◽

Wide Range ◽

Mean State ◽

The Tropical Pacific

General circulation models of the Coupled Model Intercomparison Project Phase 6 (CMIP6) are examined with respect to their ability to simulate the mean state and variability of the tropical Atlantic, as well as its linkage to the tropical Pacific. While, on average, mean state biases have improved little relative to the previous intercomparison (CMIP5), there are now a few models with very small biases. In particular the equatorial Atlantic warm SST and westerly wind biases are mostly eliminated in these models. Furthermore, interannual variability in the equatorial and subtropical Atlantic is quite realistic in a number of CMIP6 models, which suggests that they should be useful tools for understanding and predicting variability patterns. The evolution of equatorial Atlantic biases follows the same pattern as in previous model generations, with westerly wind biases during boreal spring preceding warm sea-surface temperature (SST) biases in the east during boreal summer. A substantial portion of the westerly wind bias exists already in atmosphere-only simulations forced with observed SST, suggesting an atmospheric origin. While variability is relatively realistic in many models, SSTs seem less responsive to wind forcing than observed, both on the equator and in the subtropics, possibly due to an excessively deep mixed layer originating in the oceanic component. Thus models with realistic SST amplitude tend to have excessive wind amplitude. The models with the smallest mean state biases all have relatively high resolution but there are also a few low-resolution models that perform similarly well, indicating that resolution is not the only way toward reducing tropical Atlantic biases. The results also show a relatively weak link between mean state biases and the quality of the simulated variability. The linkage to the tropical Pacific shows a wide range of behaviors across models, indicating the need for further model improvement.

A CGCM Study on the Interaction between IOD and ENSO

Journal of Climate ◽

10.1175/jcli3797.1 ◽

2006 ◽

Vol 19 (9) ◽

pp. 1688-1705 ◽

Cited By ~ 174

Author(s):

Swadhin K. Behera ◽

Jing Jia Luo ◽

Sebastien Masson ◽

Suryachandra A. Rao ◽

Hirofumi Sakuma ◽

...

Keyword(s):

Indian Ocean ◽

General Circulation ◽

Southern Oscillation ◽

Walker Circulation ◽

Tropical Pacific ◽

Boreal Summer ◽

Enso Variability ◽

The Indian Ocean ◽

Sst Anomalies ◽

The Tropical Pacific

Abstract An atmosphere–ocean coupled general circulation model known as the Scale Interaction Experiment Frontier version 1 (SINTEX-F1) model is used to understand the intrinsic variability of the Indian Ocean dipole (IOD). In addition to a globally coupled control experiment, a Pacific decoupled noENSO experiment has been conducted. In the latter, the El Niño–Southern Oscillation (ENSO) variability is suppressed by decoupling the tropical Pacific Ocean from the atmosphere. The ocean–atmosphere conditions related to the IOD are realistically simulated by both experiments including the characteristic east–west dipole in SST anomalies. This demonstrates that the dipole mode in the Indian Ocean is mainly determined by intrinsic processes within the basin. In the EOF analysis of SST anomalies from the noENSO experiment, the IOD takes the dominant seat instead of the basinwide monopole mode. Even the coupled feedback among anomalies of upper-ocean heat content, SST, wind, and Walker circulation over the Indian Ocean is reproduced. As in the observation, IOD peaks in boreal fall for both model experiments. In the absence of ENSO variability the interannual IOD variability is dominantly biennial. The ENSO variability is found to affect the periodicity, strength, and formation processes of the IOD in years of co-occurrences. The amplitudes of SST anomalies in the western pole of co-occurring IODs are aided by dynamical and thermodynamical modifications related to the ENSO-induced wind variability. Anomalous latent heat flux and vertical heat convergence associated with the modified Walker circulation contribute to the alteration of western anomalies. It is found that 42% of IOD events affected by changes in the Walker circulation are related to the tropical Pacific variabilities including ENSO. The formation is delayed until boreal summer for those IODs, which otherwise form in boreal spring as in the noENSO experiment.

Impact of the stratosphere on El Niño-Southern Oscillation

10.5194/egusphere-egu2020-21341 ◽

2020 ◽

Author(s):

Mario Rodrigo ◽

Javier Garcia-Serrano ◽

Ileana Bladé ◽

Froila M. Palmeiro ◽

Bianca Mezzina

Keyword(s):

Radiative Forcing ◽

Climate Models ◽

Climate Model ◽

Southern Oscillation ◽

Active Role ◽

Tropical Pacific ◽

Boreal Summer ◽

Enso Cycle ◽

Vertical Resolution ◽

The Tropical Pacific

The European Consortium EC-EARTH climate model version 3.1 is used to assess the effects of a well-resolved stratosphere on the representation of El Ni&#241;o-Southern Oscillation (ENSO). Three 100-year&#160; long experiments with fixed radiative forcing representative of the present climate are compared: one with the top at 0.01hPa and 91 vertical levels (HIGH-TOP), another with the top at 5hPa and 62 vertical levels (LOW-TOP), and another high-top experiment with the stratosphere nudged to the climatology of HIGH-TOP from 10hPa upwards (NUDG). The differences in vertical resolution between HIGH-TOP and LOW-TOP start at around 100hPa. This study focuses on the canonical ENSO phenomenon, which is the most important source of variability and predictability on seasonal-to-interannual timescales.&#160;Preliminary results indicate that EC-EARTH realistically simulates the ENSO SST pattern in the tropical Pacific regardless of vertical resolution, although HIGH-TOP (LOW-TOP) overestimates (underestimates) the SST variability during boreal summer (winter). In both configurations, the SST tongue is narrower meridionally and slightly shifted towards the central-western Pacific compared to observations, a common bias of climate models. Resolving the stratosphere has a clear effect on the power spectrum of the Ni&#241;o3.4 index: as compared to observations where there is a well-known frequency range of 2-7 years, HIGH-TOP and LOW-TOP have a prominent peak centered at 4-5 years but additionally both simulations display another peak, towards higher (~ 2yrs) and lower (~ 7yrs) frequencies, respectively. Another impact of including a well-resolved stratosphere is to systematically enhance the amplitude of the SST, wind and convective anomalies in the tropical Pacific throughout the entire ENSO cycle. Finally, similar differences are obtained when comparing HIGH-TOP and NUDG, suggesting an active role of the tropical stratospheric variability on ENSO.

A Regime Shift in the Interhemispheric Teleconnection between the Yellow and East China Seas and The Southeastern Tropical Pacific in The Southern Hemisphere during The Boreal Summer

10.21203/rs.3.rs-949462/v1 ◽

2021 ◽

Author(s):

Yong Sun Kim ◽

Minho Kwon ◽

Eui-Seok Chung ◽

Sang-Wook Yeh ◽

Jin-Yong Jeong ◽

...

Keyword(s):

Regime Shift ◽

Tropical Pacific ◽

Boreal Summer ◽

The North ◽

Southeastern Pacific ◽

Basin Scale ◽

Precipitation Anomalies ◽

Statistical Estimations ◽

The Tropical Pacific

Abstract Through statistical estimations on reconstructed datasets for the period 1982−2020 after removing a long-term trend, we observed that there was a drastic regime shift in the early summer’s connection between the YECS and the tropical Pacific in the early 2000s. The summer YECS SSTs had seemed to be modulated by local oceanic and atmospheric processes along with their marginal coupling to the tropical Pacific during the pre-2003 period before the regime shift. In contrast, an interhemispheric YECS−tropical southeastern Pacific (SEP) coupling appeared after the regime shift. This teleconnection was at least partially attributed to a reduced El Niño signature in the tropical Pacific, which favors the emergence of the South Pacific meridional mode (SPMM) independently from ENSO signals. Precipitation anomalies in the western tropical Pacific act as an atmospheric bridge to mediate the air-sea interacted variability associated with the SPMM into the North Pacific. The susceptibility of the YECS to atmospheric forcing may highlight the role of SST over the YECS as a potential indicator of basin-scale climate changes.

Influences of Atlantic Climate Change on the Tropical Pacific via the Central American Isthmus*

Journal of Climate ◽

10.1175/2008jcli2231.1 ◽

2008 ◽

Vol 21 (15) ◽

pp. 3914-3928 ◽

Cited By ~ 47

Author(s):

Shang-Ping Xie ◽

Yuko Okumura ◽

Toru Miyama ◽

Axel Timmermann

Keyword(s):

Climate Change ◽

North Atlantic ◽

Tropical Pacific ◽

Meridional Overturning Circulation ◽

Central American ◽

Seasonal Development ◽

Boreal Summer ◽

Turbulent Heat ◽

The Pacific ◽

The Tropical Pacific

Abstract Recent global coupled model experiments suggest that the atmospheric bridge across Central America is a key conduit for Atlantic climate change to affect the tropical Pacific. A high-resolution regional ocean–atmosphere model (ROAM) of the eastern tropical Pacific is used to investigate key processes of this conduit by examining the response to a sea surface temperature (SST) cooling over the North Atlantic. The Atlantic cooling increases sea level pressure, driving northeasterly wind anomalies across the Isthmus of Panama year-round. While the atmospheric response is most pronounced during boreal summer/fall when the tropical North Atlantic is warm and conducive to deep convection, the Pacific SST response is strongest in winter/spring when the climatological northeast trade winds prevail across the isthmus. During winter, the northeasterly cross-isthmus winds intensify in response to the Atlantic cooling, reducing the SST in the Gulf of Panama by cold and dry advection from the Atlantic and by enhancing surface turbulent heat flux and mixing. This Gulf of Panama cooling reaches the equator and is amplified by the Bjerknes feedback during boreal spring. The equatorial anomalies of SST and zonal winds dissipate quickly in early summer as the seasonal development of the cold tongue increases the stratification of the atmospheric boundary layer and shields the surface from the Atlantic influence that propagates into the Pacific as tropospheric Rossby waves. The climatological winds over the far eastern Pacific warm pool turn southwesterly in summer/fall, superimposed on which the anomalous northesterlies induce a weak SST warming there. The ROAM results are compared with global model water-hosing runs to shed light on intermodel consistency and differences in response to the shutdown of the Atlantic meridional overturning circulation. Implications for interpreting paleoclimate changes such as Heinrich events are discussed. The results presented here also aid in understanding phenomena in the present climate such as the Central American midsummer drought and Atlantic multidecadal oscillation.

Growing Coconut Palms in the Pacific Islands: Colliding Knowledge and Values

Environment and History ◽

10.3197/096734019x15755402985659 ◽

2020 ◽

Author(s):

Judith A. Bennett

Keyword(s):

Pacific Islands ◽

Social Values ◽

Coconut Oil ◽

Tropical Pacific ◽

Experiential Knowledge ◽

The West ◽

Passive Resistance ◽

The People ◽

The Pacific ◽

The Tropical Pacific

Coconuts provided commodities for the West in the form of coconut oil and copra. Once colonial governments established control of the tropical Pacific Islands, they needed revenue so urged European settlers to establish coconut plantations. For some decades most copra came from Indigenous growers. Administrations constantly urged the people to thin old groves and plant new ones like plantations, in grid patterns, regularly spaced and weeded. Local growers were instructed to collect all fallen coconuts for copra from their groves. For half a century, the administrations’ requirements met with Indigenous passive resistance. This paper examines the underlying reasons for this, elucidating Indigenous ecological and social values, based on experiential knowledge, knowledge that clashed with Western scientific values.

Fowler on Fishes of the Tropical Pacific

The American Naturalist ◽

10.1086/277907 ◽

1901 ◽

Vol 35 (412) ◽

pp. 317-318

Keyword(s):

Tropical Pacific ◽

The Tropical Pacific

Successive Modulation of ENSO to the Future Greenhouse Warming

Journal of Climate ◽

10.1175/2007jcli1500.1 ◽

2008 ◽

Vol 21 (1) ◽

pp. 3-21 ◽

Cited By ~ 55

Author(s):

Soon-Il An ◽

Jong-Seong Kug ◽

Yoo-Geun Ham ◽

In-Sik Kang

Keyword(s):

General Circulation ◽

Southern Oscillation ◽

General Circulation Models ◽

Tropical Pacific ◽

Greenhouse Warming ◽

Delayed Response ◽

Subsurface Temperature ◽

Climate System Model ◽

The Mean ◽

The Tropical Pacific

Abstract The multidecadal modulation of the El Niño–Southern Oscillation (ENSO) due to greenhouse warming has been analyzed herein by means of diagnostics of Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) coupled general circulation models (CGCMs) and the eigenanalysis of a simplified version of an intermediate ENSO model. The response of the global-mean troposphere temperature to increasing greenhouse gases is more likely linear, while the amplitude and period of ENSO fluctuates in a multidecadal time scale. The climate system model outputs suggest that the multidecadal modulation of ENSO is related to the delayed response of the subsurface temperature in the tropical Pacific compared to the response time of the sea surface temperature (SST), which would lead a modulation of the vertical temperature gradient. Furthermore, an eigenanalysis considering only two parameters, the changes in the zonal contrast of the mean background SST and the changes in the vertical contrast between the mean surface and subsurface temperatures in the tropical Pacific, exhibits a good agreement with the CGCM outputs in terms of the multidecadal modulations of the ENSO amplitude and period. In particular, the change in the vertical contrast, that is, change in difference between the subsurface temperature and SST, turns out to be more influential on the ENSO modulation than changes in the mean SST itself.