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Paul Spence - One of the best experts on this subject based on the ideXlab platform.
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Role of Pacific Trade Winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Climate Dynamics, 2018Co-Authors: Nicola Maher, Matthew H. England, Arjun Gupta, Paul SpenceAbstract:Interannual to decadal variability in the Pacific Ocean is a prominent feature of Earth’s climate system, with global teleconnections. Recent studies have identified Pacific decadal variability as a major driver of periods of rapid and slower global mean surface air temperature change. Here, we use an eddy-permitting global ocean model to investigate the role of the observed 1992–2011 Trade wind intensification and concurrent trends in surface atmospheric variables over the Pacific associated with the negative phase of the Interdecadal Pacific Oscillation (IPO) in driving ocean circulation and heat content changes. We find a strengthening of the Equatorial Undercurrent (EUC) in response to strengthened Winds, which brings cooler water to the surface of the eastern Pacific and an increase in the Pacific shallow overturning cells (PSOC), which in turn drives additional heat into the subsurface western Pacific. The wind acceleration also results in an increase in the strength and subsequent heat transport of the Indonesian throughflow (ITF), which transports some of the additional heat from the western Pacific into the Indian Ocean. The circulation changes result in warming of the subsurface western Pacific, cooling of the upper eastern Pacific Ocean and warming of the subsurface Indian Ocean, with an overall increase in Indo-Pacific heat content. Further experiments impose a symmetric reversal of the atmospheric state to examine how the ocean would behave if the Winds (and other atmospheric variables) were to revert to their initial state. This mimics a return to the neutral phase of the IPO, characterised by a weakening of the Pacific Trade Winds. In response we find a slowdown of the EUC and the PSOC, which results in a return to climatological SST conditions in the western and eastern Pacific. The ITF also slows towards its original strength. However, the subsurface temperature, heat content and ITF responses are not symmetric due to an overall increase in the surface heat flux into the ocean associated with the cooler surface of the Pacific. There may also be irreversible heat transport across the thermocline via diapycnal mixing, further contributing to this asymmetry. The net result of the experiment is that the Indo-Pacific subsurface ocean is warmer than it was in its initial state.
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Role of Pacific Trade Winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Climate Dynamics, 2017Co-Authors: Nicola Maher, Matthew H. England, Alex Sen Gupta, Paul SpenceAbstract:Interannual to decadal variability in the Pacific Ocean is a prominent feature of Earth’s climate system, with global teleconnections. Recent studies have identified Pacific decadal variability as a major driver of periods of rapid and slower global mean surface air temperature change. Here, we use an eddy-permitting global ocean model to investigate the role of the observed 1992–2011 Trade wind intensification and concurrent trends in surface atmospheric variables over the Pacific associated with the negative phase of the Interdecadal Pacific Oscillation (IPO) in driving ocean circulation and heat content changes. We find a strengthening of the Equatorial Undercurrent (EUC) in response to strengthened Winds, which brings cooler water to the surface of the eastern Pacific and an increase in the Pacific shallow overturning cells (PSOC), which in turn drives additional heat into the subsurface western Pacific. The wind acceleration also results in an increase in the strength and subsequent heat transport of the Indonesian throughflow (ITF), which transports some of the additional heat from the western Pacific into the Indian Ocean. The circulation changes result in warming of the subsurface western Pacific, cooling of the upper eastern Pacific Ocean and warming of the subsurface Indian Ocean, with an overall increase in Indo-Pacific heat content. Further experiments impose a symmetric reversal of the atmospheric state to examine how the ocean would behave if the Winds (and other atmospheric variables) were to revert to their initial state. This mimics a return to the neutral phase of the IPO, characterised by a weakening of the Pacific Trade Winds. In response we find a slowdown of the EUC and the PSOC, which results in a return to climatological SST conditions in the western and eastern Pacific. The ITF also slows towards its original strength. However, the subsurface temperature, heat content and ITF responses are not symmetric due to an overall increase in the surface heat flux into the ocean associated with the cooler surface of the Pacific. There may also be irreversible heat transport across the thermocline via diapycnal mixing, further contributing to this asymmetry. The net result of the experiment is that the Indo-Pacific subsurface ocean is warmer than it was in its initial state. © 2017 The Author(s
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recent intensification of wind driven circulation in the pacific and the ongoing warming hiatus
Nature Climate Change, 2014Co-Authors: Matthew H. England, Axel Timmermann, Shayne Mcgregor, Alex Sen Gupta, Paul Spence, Gerald A Meehl, Wenju Cai, Michael J Mcphaden, Ariaan Purich, Agus SantosoAbstract:The slowdown in global average surface warming has recently been linked to sea surface cooling in the eastern Pacific Ocean. This work shows that strengthening Trade Winds caused a reduction in the 2012 global average surface air temperature of 0.1–0.2 °C. This may account for much of the warming hiatus and is a result of increased subsurface ocean heat uptake.
Deliang Chen - One of the best experts on this subject based on the ideXlab platform.
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Wind speed variability over the Canary Islands, 1948–2014: focusing on trend differences at the land–ocean interface and below–above the Trade-wind inversion layer
Climate Dynamics, 2017Co-Authors: Cesar Azorin-molina, Melisa Menéndez, Tim R. Mcvicar, Adrian Acevedo, Sergio M. Vicente-serrano, Emilio Cuevas, Lorenzo Minola, Deliang ChenAbstract:This study simultaneously examines wind speed trends at the land–ocean interface, and below–above the Trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of Trade-Winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981–2014), including one mountain weather station (Izana) located above the Trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948–2014; and SeaWind II at 15 km for 1989–2014). The results revealed a widespread significant negative trend of Trade-Winds over ocean for 1948–2014, whereas no significant trends were detected for 1989–2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter–spring–autumn; significant in April and September) of Trade-Winds. Above the inversion layer at Izana, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.
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Wind speed variability over the Canary Islands, 1948–2014: focusing on trend differences at the land–ocean interface and below–above the Trade-wind inversion layer
Climate Dynamics, 2017Co-Authors: Cesar Azorin-molina, Melisa Menéndez, Tim R. Mcvicar, Adrian Acevedo, Sergio M. Vicente-serrano, Emilio Cuevas, Lorenzo Minola, Deliang ChenAbstract:This study simultaneously examines wind speed trends at the land–ocean interface, and below–above the Trade-wind inversion layer in the Canary Islands and the surrounding Eastern North Atlantic Ocean: a key region for quantifying the variability of Trade-Winds and its response to large-scale atmospheric circulation changes. Two homogenized data sources are used: (1) observed wind speed from nine land-based stations (1981–2014), including one mountain weather station (Izaña) located above the Trade-wind inversion layer; and (2) simulated wind speed from two atmospheric hindcasts over ocean (i.e., SeaWind I at 30 km for 1948–2014; and SeaWind II at 15 km for 1989–2014). The results revealed a widespread significant negative trend of Trade-Winds over ocean for 1948–2014, whereas no significant trends were detected for 1989–2014. For this recent period wind speed over land and ocean displayed the same multi-decadal variability and a distinct seasonal trend pattern with a strengthening (late spring and summer; significant in May and August) and weakening (winter–spring–autumn; significant in April and September) of Trade-Winds. Above the inversion layer at Izaña, we found a predominance of significant positive trends, indicating a decoupled variability and opposite wind speed trends when compared to those reported in boundary layer. The analysis of the Trade Wind Index (TWI), the North Atlantic Oscillation Index (NAOI) and the Eastern Atlantic Index (EAI) demonstrated significant correlations with the wind speed variability, revealing that the correlation patterns of the three indices showed a spatio-temporal complementarity in shaping wind speed trends across the Eastern North Atlantic.C. A. -M. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 703733 (STILLING project). This research was also supported by the Research Projects: Swedish BECC, MERGE, VR (2014–5320), PCIN-2015-220, CGL2014-52135-C03-01 and Red de variabilidad y cambio climático RECLIM (CGL2014-517221-REDT). M.M is indebted to the Spanish Government for funding through the “Ramón y Cajal” program and supported by Grant PORTIO (BIA2015-70644-R)
Matthew H. England - One of the best experts on this subject based on the ideXlab platform.
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Role of Pacific Trade Winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Climate Dynamics, 2018Co-Authors: Nicola Maher, Matthew H. England, Arjun Gupta, Paul SpenceAbstract:Interannual to decadal variability in the Pacific Ocean is a prominent feature of Earth’s climate system, with global teleconnections. Recent studies have identified Pacific decadal variability as a major driver of periods of rapid and slower global mean surface air temperature change. Here, we use an eddy-permitting global ocean model to investigate the role of the observed 1992–2011 Trade wind intensification and concurrent trends in surface atmospheric variables over the Pacific associated with the negative phase of the Interdecadal Pacific Oscillation (IPO) in driving ocean circulation and heat content changes. We find a strengthening of the Equatorial Undercurrent (EUC) in response to strengthened Winds, which brings cooler water to the surface of the eastern Pacific and an increase in the Pacific shallow overturning cells (PSOC), which in turn drives additional heat into the subsurface western Pacific. The wind acceleration also results in an increase in the strength and subsequent heat transport of the Indonesian throughflow (ITF), which transports some of the additional heat from the western Pacific into the Indian Ocean. The circulation changes result in warming of the subsurface western Pacific, cooling of the upper eastern Pacific Ocean and warming of the subsurface Indian Ocean, with an overall increase in Indo-Pacific heat content. Further experiments impose a symmetric reversal of the atmospheric state to examine how the ocean would behave if the Winds (and other atmospheric variables) were to revert to their initial state. This mimics a return to the neutral phase of the IPO, characterised by a weakening of the Pacific Trade Winds. In response we find a slowdown of the EUC and the PSOC, which results in a return to climatological SST conditions in the western and eastern Pacific. The ITF also slows towards its original strength. However, the subsurface temperature, heat content and ITF responses are not symmetric due to an overall increase in the surface heat flux into the ocean associated with the cooler surface of the Pacific. There may also be irreversible heat transport across the thermocline via diapycnal mixing, further contributing to this asymmetry. The net result of the experiment is that the Indo-Pacific subsurface ocean is warmer than it was in its initial state.
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Role of Pacific Trade Winds in driving ocean temperatures during the recent slowdown and projections under a wind trend reversal
Climate Dynamics, 2017Co-Authors: Nicola Maher, Matthew H. England, Alex Sen Gupta, Paul SpenceAbstract:Interannual to decadal variability in the Pacific Ocean is a prominent feature of Earth’s climate system, with global teleconnections. Recent studies have identified Pacific decadal variability as a major driver of periods of rapid and slower global mean surface air temperature change. Here, we use an eddy-permitting global ocean model to investigate the role of the observed 1992–2011 Trade wind intensification and concurrent trends in surface atmospheric variables over the Pacific associated with the negative phase of the Interdecadal Pacific Oscillation (IPO) in driving ocean circulation and heat content changes. We find a strengthening of the Equatorial Undercurrent (EUC) in response to strengthened Winds, which brings cooler water to the surface of the eastern Pacific and an increase in the Pacific shallow overturning cells (PSOC), which in turn drives additional heat into the subsurface western Pacific. The wind acceleration also results in an increase in the strength and subsequent heat transport of the Indonesian throughflow (ITF), which transports some of the additional heat from the western Pacific into the Indian Ocean. The circulation changes result in warming of the subsurface western Pacific, cooling of the upper eastern Pacific Ocean and warming of the subsurface Indian Ocean, with an overall increase in Indo-Pacific heat content. Further experiments impose a symmetric reversal of the atmospheric state to examine how the ocean would behave if the Winds (and other atmospheric variables) were to revert to their initial state. This mimics a return to the neutral phase of the IPO, characterised by a weakening of the Pacific Trade Winds. In response we find a slowdown of the EUC and the PSOC, which results in a return to climatological SST conditions in the western and eastern Pacific. The ITF also slows towards its original strength. However, the subsurface temperature, heat content and ITF responses are not symmetric due to an overall increase in the surface heat flux into the ocean associated with the cooler surface of the Pacific. There may also be irreversible heat transport across the thermocline via diapycnal mixing, further contributing to this asymmetry. The net result of the experiment is that the Indo-Pacific subsurface ocean is warmer than it was in its initial state. © 2017 The Author(s
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Recent Walker circulation strengthening and Pacific cooling amplified by Atlantic warming
Nature Climate Change, 2014Co-Authors: Shayne Mcgregor, Axel Timmermann, Malte F. Stuecker, Matthew H. England, Mark A. Merrifield, Fei-fei Jin, Yoshimitsu ChikamotoAbstract:The Pacific Trade Winds have strengthened since the late 1990s, and there has been related strengthening of the atmospheric Walker circulation. Although the impacts of these changes are becoming known, their cause has not been identified. This study, using observations and models, shows that warming of the Atlantic sea surface and corresponding displacement of atmospheric pressure centres are key drivers.
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recent intensification of wind driven circulation in the pacific and the ongoing warming hiatus
Nature Climate Change, 2014Co-Authors: Matthew H. England, Axel Timmermann, Shayne Mcgregor, Alex Sen Gupta, Paul Spence, Gerald A Meehl, Wenju Cai, Michael J Mcphaden, Ariaan Purich, Agus SantosoAbstract:The slowdown in global average surface warming has recently been linked to sea surface cooling in the eastern Pacific Ocean. This work shows that strengthening Trade Winds caused a reduction in the 2012 global average surface air temperature of 0.1–0.2 °C. This may account for much of the warming hiatus and is a result of increased subsurface ocean heat uptake.
Ralph R Schneider - One of the best experts on this subject based on the ideXlab platform.
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Reconstruction of SE Trade-wind intensity based on sea-surface temperature gradients in the Southeast Atlantic over the last 25 kyr
Geophysical Research Letters, 2003Co-Authors: J H Kim, Ralph R Schneider, Stefan Mulitza, Peter J MüllerAbstract:[1] A prominent feature in the Southeast Atlantic is the Angola-Benguela Front (ABF), the convergence between warm tropical and cold subtropical upwelled waters. At present, the sea-surface temperature (SST) gradient across the ABF and its position are influenced by the strength of southeasterly (SE) Trade Winds. Here, we present a record of changes in the ABF SST gradient over the last 25 kyr. Variations in this SST contrast indicate that periods of strengthened SE Trade-wind intensity occurred during the Last Glacial Maximum, the Younger Dryas, and the Mid to Late Holocene, while Heinrich Event 1, the early part of the Bolling-Allerod, and the Early Holocene were periods of weakened SE Trade-Winds.
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low latitude control of interhemispheric sea surface temperature contrast in the tropical atlantic over the past 21 kyears the possible role of se Trade Winds
Climate Dynamics, 2003Co-Authors: J H Kim, Ralph R SchneiderAbstract:To stimulate a discussion on the role of tropical atmospheric circulation versus thermohaline circulation changes for tropical Atlantic sea-surface temperature (SST) variations, we present a record of the SST contrast (ΔSST) between the tropical northwest and southeast Atlantic from the Last Glacial Maximum to the Late Holocene. The ΔSST was calculated from two alkenone-derived SST records; one from the Caribbean Sea and the other from the Angola Basin. Changes in the cross-equatorial ΔSST were then compared with an abundance record of Florisphaera profunda from the equatorial Atlantic, which is indicative of SE Trade-wind induced variations in thermocline depth in the equatorial divergence zone. This comparison implies that the Last Glacial Maximum, the Younger Dryas, and the Mid to Late Holocene were periods of strong SE Trade Winds, which led to an intense upwelling-related cooling in the southeast Atlantic and concurrently enhanced advection of warm tropical South Atlantic waters into the western tropical Atlantic. Accordingly, a coupled ocean-atmospheric process has probably created a dipole-like SST distribution pattern in the tropical Atlantic during these three distinct climatic periods. In contrast, Heinrich Event 1, the Bolling-Allerod, and the Early Holocene were intervals of weakened SE Trade Winds, causing a warming in the southeast Atlantic. However, synchronous warming in both regions during Heinrich Event 1 can be partially attributed to a weakening of thermohaline overturning which caused a reduced northward heat transport from the low-latitude to the high-latitude North Atlantic.
Yukio Masumoto - One of the best experts on this subject based on the ideXlab platform.
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the reversal of the multi decadal trends of the equatorial pacific easterly Winds and the indonesian throughflow and leeuwin current transports
Geophysical Research Letters, 2011Co-Authors: Ming Feng, Yukio Masumoto, Claus W Boning, Arne Biastoch, Erik Behrens, Evan WellerAbstract:Multi-decadal weakening trend of the equatorial Pacific easterly Winds since 1960 has reversed after 1993. The trend reversal has induced cooling (shallow thermocline) trend in the equatorial western Pacific before 1993, followed by a warming (deep thermocline) trend from 1993 to the present. All available atmospheric reanalysis products corroborate the trend reversal during the two multi-decadal periods. The magnitudes of the multi-decadal trends of the easterly Winds, however, differ among the reanalysis products. The trend reversals of regional ocean circulations are assessed using linear regressions between wind and transport anomalies in an eddy-permitting numerical model, suggesting that since 1993 the Indonesian Throughflow and the Leeuwin Current transports have also reversed their multi-decadal weakening trends. Key Points: - There have been reversals of the multi-decadal weakening trends of Trade Winds - Different reanalysis products capture different trends in Trade Winds
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seasonal variations of the hawaiian lee countercurrent induced by the meridional migration of the Trade Winds
Ocean Dynamics, 2010Co-Authors: Hideharu Sasaki, Bunmei Taguchi, Masami Nonaka, Yukio MasumotoAbstract:Seasonal variations of the Hawaiian Lee Countercurrent (HLCC) are investigated using satellite observations of sea surface height and wind stress as well as eddy-resolving ocean model simulations. The HLCC is strong from summer to winter and weak in spring between the dateline and the Hawaiian Islands. In response to the seasonal migration of the northeast Trade Winds in the meridional direction, the wind curl dipole lee of Hawaii varies in strength, exciting westward-propagating Rossby waves. The analyses of both observations and simulations show that the propagation of Rossby waves south of the HLCC, driven by the southern pole of the wind curl dipole in the lee of the islands, contributes the most to the seasonal variations of the HLCC. Unlike the wind-driven seasonal variations, our analysis suggests that other mechanisms such as mode water intrusion or air–sea interaction may cause the interannual variations of the HLCC.
