Mechanisms of Arctic Surface Air Temperature Change in Response to the Madden–Julian Oscillation

2012 ◽  
Vol 25 (17) ◽  
pp. 5777-5790 ◽  
Author(s):  
Changhyun Yoo ◽  
Sukyoung Lee ◽  
Steven B. Feldstein
Keyword(s):  
Heat Flux ◽  
Air Temperature ◽  
Phase 1 ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Boreal Winter ◽  
Convective Heating ◽  
Madden Julian Oscillation ◽  
Eddy Heat Flux ◽  
Arctic Surface

Abstract Using lagged composites and projections with the thermodynamic energy equation, in this study the mechanisms that drive the boreal winter Arctic surface air temperature (SAT) change associated with the Madden–Julian oscillation (MJO) are investigated. The Wheeler and Hendon MJO index, which divides the MJO into 8 phases, where phase 1 (phase 5) corresponds to reduced (enhanced) convection over the Maritime Continent and western Pacific Ocean, is used. It is shown that the more zonally localized (uniform) tropical convective heating associated with MJO phase 5 (phase 1) leads to enhanced (reduced) excitation of poleward-propagating Rossby waves, which contribute to Arctic warming (cooling). Adiabatic warming/cooling, eddy heat flux, and the subsequent change in downward infrared radiation (IR) flux are found to be important for the Arctic SAT change. The adiabatic warming/cooling initiates the Arctic SAT change, however, subsequent eddy heat flux makes a greater contribution. The resulting SAT change is further amplified by alteration in downward IR. It is shown that changes in surface sensible and latent heat fluxes oppose the contribution by the above processes.

scholarly journals Mechanism of Seasonal Arctic Sea Ice Evolution and Arctic Amplification

2016 ◽  
Author(s):  
Kwang-Yul Kim ◽  
Benjamin D. Hamlington ◽  
Hanna Na ◽  
Jinju Kim
Keyword(s):  
Heat Flux ◽  
Sea Ice ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Longwave Radiation ◽  
The Arctic ◽  
Turbulent Heat ◽  
Arctic Amplification ◽  
Ice Melting ◽  
Downward Longwave Radiation

Abstract. Sea ice melting is proposed as a primary reason for the Artic amplification, although physical mechanism of the Arctic amplification and its connection with sea ice melting is still in debate. In the present study, monthly ERA-interim reanalysis data are analyzed via cyclostationary empirical orthogonal function analysis to understand the seasonal mechanism of sea ice melting in the Arctic Ocean and the Arctic amplification. While sea ice melting is widespread over much of the perimeter of the Arctic Ocean in summer, sea ice remains to be thin in winter only in the Barents-Kara Seas. Excessive turbulent heat flux through the sea surface exposed to air due to sea ice melting warms the atmospheric column. Warmer air increases the downward longwave radiation and subsequently surface air temperature, which facilitates sea surface remains to be ice free. A 1 % reduction in sea ice concentration in winter leads to ~ 0.76 W m−2 increase in upward heat flux, ~ 0.07 K increase in 850 hPa air temperature, ~ 0.97 W m−2 increase in downward longwave radiation, and ~ 0.26 K increase in surface air temperature. This positive feedback mechanism is not clearly observed in the Laptev, East Siberian, Chukchi, and Beaufort Seas, since sea ice refreezes in late fall (November) before excessive turbulent heat flux is available for warming the atmospheric column in winter. A detailed seasonal heat budget is presented in order to understand specific differences between the Barents-Kara Seas and Laptev, East Siberian, Chukchi, and Beaufort Seas.

Arctic Response to an MJO-Like Tropical Heating in an Idealized GCM

2012 ◽  
Vol 69 (8) ◽  
pp. 2379-2393 ◽  
Author(s):  
Changhyun Yoo ◽  
Sukyoung Lee ◽  
Steven B. Feldstein
Keyword(s):  
General Circulation ◽  
Phase 1 ◽  
Initial Perturbation ◽  
Circulation Model ◽  
The Arctic ◽  
Model Calculations ◽  
Initial Flow ◽  
Eddy Heat Flux ◽  
Arctic Surface ◽  
Tropical Heating

Abstract Using an initial-value approach with an idealized general circulation model, the mechanisms by which the Madden–Julian oscillation (MJO) influences the Arctic surface air temperature (SAT) are investigated. Model calculations corresponding to MJO phases 1 and 5 are performed, as previous studies have shown that these two phases are associated with a cooling and warming of the Arctic surface, respectively. Observed MJO-like tropical heating profiles are specified, with the phase 5 (phase 1) heating taking on a more zonally localized (uniform) spatial structure. A large ensemble of model runs is performed, where the initial flow of each ensemble member consists of the winter climatology together with an initial perturbation that is selected randomly from observational data. The model calculations show that MJO phase 5 (phase 1) is followed by a strengthening (weakening) in the poleward wave activity propagation out of the tropics, which leads to an increase (decrease) in Arctic SAT. Examination of the corresponding eddy momentum flux convergence and mass streamfunction fields shows that an eddy-induced mean meridional circulation warms (cools) the Arctic for phase 5 (phase 1). Further Arctic warming (cooling) takes place through changes in the planetary-scale, poleward eddy heat flux. In addition, calculations with a passive tracer added to the model show an increase (decrease) in the high-latitude tracer concentration for MJO phase 5 (phase 1). These results suggest that the observed changes in Arctic downward infrared radiation associated with the MJO may be associated with changes in poleward moisture transport.

scholarly journals Offsetting effects of aerosols on Arctic and global climate in the late 20th century

2014 ◽  
Vol 14 (8) ◽  
pp. 3969-3975 ◽  
Author(s):  
Q. Yang ◽  
C. M. Bitz ◽  
S. J. Doherty
Keyword(s):  
20Th Century ◽  
Air Temperature ◽  
Radiative Forcing ◽  
Global Climate ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Late 20Th Century ◽  
Climate Effect ◽  
Climate System Model ◽  
Arctic Surface

Abstract. We examine the impacts of atmospheric aerosols on Arctic and global climate using a series of 20th century transient simulations from Community Climate System Model version 4 (CCSM4). We focus on the response of surface air temperature to the direct radiative forcing driven by changes in sulfate and black carbon (BC) concentrations from 1975 to 2005 and we also examine the response to changes in sulfate, BC, and organic carbon (OC) aerosols collectively. The direct forcing from sulfate dominates the aerosol climate effect. Globally averaged, simultaneous changes in all three aerosols produce a cooling trend of 0.015 K decade−1 during the period 1975–2005. In the Arctic, surface air temperature has large spatial variations in response to changes in aerosol concentrations. Over the European Arctic, aerosols induce about 0.6 K decade−1 warming, which is about 1.8 K warming over the 30-year period. This warming is triggered mainly by the reduction in sulfate and BC emissions over Europe since the 1970s and is reinforced by sea ice loss and a strengthening in atmospheric northward heat transport. Changes in sulfate concentrations account for about two thirds of the warming and BC for the remaining one third. Over the Siberian and North American Arctic, surface air temperature is likely influenced by changes in aerosol concentrations over Asia. An increase in sulfate optical depth over Asia induces a large cooling while an increase in BC over Asia causes a significant warming.

scholarly journals Offsetting effects of aerosols on Arctic and global climate in the late 20th century

2013 ◽  
Vol 13 (11) ◽  
pp. 30929-30943
Author(s):  
Q. Yang ◽  
C. M. Bitz ◽  
S. J. Doherty
Keyword(s):  
20Th Century ◽  
Air Temperature ◽  
Radiative Forcing ◽  
Global Climate ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Late 20Th Century ◽  
Climate Effect ◽  
Climate System Model ◽  
Arctic Surface

Abstract. We examine the impacts of atmospheric aerosols on Arctic and global climate using a series of 20th century transient simulations from Community Climate System Model version 4 (CCSM4). We focus on the response of surface air temperature to the direct radiative forcing driven by changes in sulfate and black carbon (BC) concentrations from 1975 to 2005 and we also examine the response to sulfate, BC, and organic carbon aerosols varying at once. The direct forcing from sulfate dominates the aerosol climate effect. Globally averaged, all three aerosols produce a cooling trend of 0.015 K decade−1 during the period 1975–2005. In the Arctic, surface air temperature has large spatial variations in response to changes in aerosol concentrations. Over the European Arctic, aerosols induce about 0.6 K decade−1 warming which is about 1.8 K warming over the 30 yr period. This warming is triggered mainly by the reduction in sulfate and BC emissions over Europe since the 1970s and is reinforced by sea ice loss and a strengthening in atmospheric northward heat transport. Over the Siberian and North American Arctic, surface air temperature is likely influenced primarily by changes in aerosol emissions from Asia. An increase in sulfate emissions over Asia induces a large cooling while an increase in BC over Asia causes a significant warming.

Late 20th century increase in northern Svalbard glacier-derived runoff tracked by encrusting coralline algae

2020 ◽  
Author(s):  
Steffen Hetzinger ◽  
Jochen Halfar ◽  
Zoltan Zajacz ◽  
Marco Möller ◽  
Max Wisshak
Keyword(s):  
Global Warming ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
High Arctic ◽  
Climate System ◽  
Coralline Algae ◽  
The Arctic ◽  
Surface Ocean ◽  
The Impact ◽  
Arctic Surface

<p>The Arctic cryosphere is changing at a rapid pace due to global warming and the large-scale changes observed in the Arctic during the past decades exert a strong influence throughout the global climate system. The warming of Arctic surface air temperatures is more than twice as large as the global average over the last two decades and recent events indicate new extremes in the Arctic climate system, e.g. for the last five years Arctic annual surface air temperature exceeded that of any year since 1900 AD. Northern Spitsbergen, Svalbard, located in the High Arctic at 80°N, is a warming hotspot with an observed temperature rise of ~6°C over the last three decades indicating major global warming impacts. However, even the longest available datasets on Svalbard climatic conditions do not extend beyond the 1950s, inhibiting the study of long-term natural variability before anthropogenic influence. Ongoing climate trends strongly affect the state of both glaciers and seasonal snow in Svalbard. Modeled data suggest a marked increase in glacier runoff during recent decades in northern Svalbard. However, observational data are sparse and short and the potential effects on the surface ocean are unclear.<br>This study focuses on the ultra-high-resolution analysis of calcified coralline algal buildups growing attached to the shallow seafloor along Arctic coastlines. Analysis of these new annually-layered climate archives is based on the long-lived encrusting coralline algae <em>Clathromorphum compactum</em>, providing a historic perspective on recently observed changes. Here, we present a 200-year record of past surface ocean variability from Mosselbukta, Spitsbergen, northern Svalbard. By using algal Ba/Ca ratios as a proxy for past glacier-derived meltwater input, we investigate past multi-decadal-scale fluctuations in land-based freshwater contributions to the ocean surface layer. Our records, based on multiple coralline algal specimens, show a strong and statistically significant increasing trend in algal Ba/Ca ratios from the 1990s onwards, suggesting a drastic increase in land-based runoff at Mosselbukta. The drastic rate of increase is unprecedented during the last two centuries, directly capturing the impact of amplified surface air temperature warming on coastal high Arctic surface ocean environments.</p><p> </p>

scholarly journals Multidecadal Changes in the Influence of the Arctic Oscillation on the East Asian Surface Air Temperature in Boreal Winter

Atmosphere ◽  
2019 ◽  
Vol 10 (12) ◽  
pp. 757 ◽  
Author(s):  
Hainan Gong ◽  
Lin Wang ◽  
Wen Chen
Keyword(s):  
East Asia ◽  
Air Temperature ◽  
North Pacific ◽  
Arctic Oscillation ◽  
Regional Climate ◽  
East Asian ◽  
Surface Air Temperature ◽  
The Arctic ◽  
Boreal Winter ◽  
The Impact

The time-varying influences of the wintertime Arctic Oscillation (AO) on the concurrent East Asian surface air temperature (EAT) are investigated based on JRA-55 reanalysis data. Results reveal that there are multidecadal variations in the influences of wintertime AO on the EAT during 1958–2018. Before the mid-1980s, the impact of winter AO on the simultaneous EAT is weak and confined northward of 40° N over East Asia. After the mid-1980s, by contrast, the winter AO’s influence is stronger and can extend southward of 25° N over East Asia. The multidecadal variations of the winter AO–EAT relationship are mainly modulated by the magnitudes of the North Pacific center of the winter AO. During the periods with strong North Pacific center of the winter AO, in association with the positive phase of the winter AO, the low-level southeasterly anomalies on the west side of the anticyclone over North Pacific bring warm air from the ocean to East Asia and lead to a significant winter AO–EAT relationship. In contrast, the southerly anomalies are weak and even reversed to northerly over the coast of East Asia during the periods with weak North Pacific center of winter AO, which confines the influence of winter AO on northern East Asia and lead to an insignificant winter AO–EAT relationship. Our finding provides new insight into the understanding of the decadal changes of AO’s impacts on the regional climate.

scholarly journals Mapping the Relationship between Northern Hemisphere Winter Surface Air Temperature and the Madden–Julian Oscillation

2011 ◽  
Vol 139 (8) ◽  
pp. 2439-2454 ◽  
Author(s):  
Yang Zhou ◽  
Keith R. Thompson ◽  
Youyu Lu
Keyword(s):  
North America ◽  
Linear Model ◽  
Air Temperature ◽  
Surface Air Temperature ◽  
Boreal Winter ◽  
Eastern North America ◽  
Madden Julian Oscillation ◽  
State Variables ◽  
Normal Surface ◽  
The Tropics

AbstractA regression-based modeling approach is described for mapping the dependence of atmospheric state variables such as surface air temperature (SAT) on the Madden–Julian oscillation (MJO). For the special case of a linear model the dependence can be described by two maps corresponding to the amplitude and lag of the mean atmospheric response with respect to the MJO. In this sense the method leads to a more parsimonious description than traditional compositing, which usually results in eight maps, one for each MJO phase. Another advantage of the amplitude and phase maps is that they clearly identify propagating signals, and also regions where the response is strongly amplified or attenuated. A straightforward extension of the linear model is proposed to allow the amplitude and phase of the response to vary with the amplitude of the MJO or indices that define the background state of the atmosphere–ocean system. Application of the approach to global SAT for boreal winter clearly shows the propagation of MJO-related signals in both the tropics and extratropics and an enhanced response over eastern North America and Alaska (further enhanced during La Niña years). The SAT response over Alaska and eastern North America is caused mainly by horizontal advection related to variations in shore-normal surface winds that, in turn, can be traced (via signals in the 500-hPa geopotential height) back to MJO-related disturbances in the tropics.

Testing of the Tropically Excited Arctic Warming Mechanism (TEAM) with Traditional El Niño and La Niña

2012 ◽  
Vol 25 (12) ◽  
pp. 4015-4022 ◽  
Author(s):  
Sukyoung Lee
Keyword(s):  
Air Temperature ◽  
El Niño ◽  
Energy Transport ◽  
El Nino ◽  
Surface Air Temperature ◽  
La Niña ◽  
The Arctic ◽  
Convective Heating ◽  
Arctic Warming ◽  
La Nina

Abstract By analyzing El Niño and La Niña composites with 40-yr European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis (ERA-40) data, evidence is presented here that the surface air temperature of the Arctic winter (December–February) is anomalously warm during La Niña and cold during El Niño. Surface and top-of-the-atmosphere energy fluxes were used to calculate the composite zonal-mean poleward moist static energy transport. The result shows that the La Niña warming in the Arctic is associated with an increased poleward energy transport in the extratropics. The opposite characteristics are found for El Niño. Because the total tropical convective heating is more localized during La Niña than El Niño, these findings suggest that the Arctic surface air temperature anomalies associated with ENSO may be attributed to the tropically excited Arctic warming mechanism (TEAM). In the tropics, consistent with previous studies, the anomalous poleward energy transport is positive during El Niño and negative during La Niña. Given the debate over whether a warmer world would take on more El Niño–like or La Niña–like characteristics, the findings of this study underscore the need for further investigation of tropical influence on polar climate.

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