scholarly journals Connection between Sea Surface Anomalies and Atmospheric Quasi-Stationary Waves

2020 ◽  
Vol 33 (1) ◽  
pp. 201-212
Author(s):  
G. Wolf ◽  
A. Czaja ◽  
D. J. Brayshaw ◽  
N. P. Klingaman
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Late Summer ◽  
Ice Cover ◽  
Sea Surface ◽  
Late Winter ◽  
Driving Mechanism ◽  
The North ◽  
The North Atlantic

AbstractLarge-scale, quasi-stationary atmospheric waves (QSWs) are known to be strongly connected with extreme events and general weather conditions. Yet, despite their importance, there is still a lack of understanding about what drives variability in QSW. This study is a step toward this goal, and it identifies three statistically significant connections between QSWs and sea surface anomalies (temperature and ice cover) by applying a maximum covariance analysis technique to reanalysis data (1979–2015). The two most dominant connections are linked to El Niño–Southern Oscillation and the North Atlantic Oscillation. They confirm the expected relationship between QSWs and anomalous surface conditions in the tropical Pacific and the North Atlantic, but they cannot be used to infer a driving mechanism or predictability from the sea surface temperature or the sea ice cover to the QSW. The third connection, in contrast, occurs between late winter to early spring Atlantic sea ice concentrations and anomalous QSW patterns in the following late summer to early autumn. This new finding offers a pathway for possible long-term predictability of late summer QSW occurrence.

scholarly journals Recent weakening in the winter ENSO teleconnection over the North Atlantic-European region

2021 ◽  
Author(s):  
Sara Ivasić ◽  
Ivana Herceg Bulić ◽  
Martin P. King
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Southern Oscillation ◽  
Recent Change ◽  
Late Winter ◽  
The North ◽  
Enso Teleconnections ◽  
Area Of Interest ◽  
The North Atlantic

<p>New observational evidence for variability of the atmospheric response to wintertime El Niño-Southern Oscillation (ENSO) is found. A weakening in the recent ENSO teleconnection over the North Atlantic-European (NAE) region is demonstrated by using various methods (e.g. composite analysis, running correlation, regression maps) applied onto different observational datasets and reanalyses (HadSLP, NOAA 20th Century reanalysis). Changes in both the spatial pattern and strength of the ENSO teleconnection indicate a turning point in the 1970s, with a shift from a response resembling the North Atlantic Oscillation (NAO) in late winter to an anomaly pattern with very weak or statistically non-significant values; and to nearly non-existent teleconnection in the most recent decades. Weakening of the ENSO signal is found at the surface (sea level pressure), but also at higher levels for different variables (geopotential height, temperature, zonal wind). To offer a possible reason behind the observed change, we have investigated the potential role of sea-ice and SST climatology in modulating the ENSO-NAE teleconnection. Sensitivity experiments made with a GCM of indermediate complexity (ICTP AGCM) using different combinations of sea-ice and sea surface temperature (SST) climatology conditions enabled the investigation of their respective roles. As indicated by the targeted simulations, recent change in the SST climatology in the Atlantic and Arctic has contributed to the weakening of the ENSO effect. Results highlight the importance of the background SST state and sea-ice climatology having opposite effects in modulating the ENSO-NAE teleconnection over the area of interest. The findings of this study could further our understanding of modulations of ENSO teleconnections and the role of ENSO as a source of predictability in the NAE sector.</p>

Erratum to: An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation

2017 ◽  
Vol 50 (1-2) ◽  
pp. 443-443 ◽  
Author(s):  
Mihaela Caian ◽  
Torben Koenigk ◽  
Ralf Döscher ◽  
Abhay Devasthale
Keyword(s):  
Sea Ice ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The North ◽  
Arctic Sea ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

scholarly journals The link between the Barents Sea and ENSO events simulated by NEMO model

Ocean Science ◽  
2012 ◽  
Vol 8 (6) ◽  
pp. 971-982 ◽  
Author(s):  
V. N. Stepanov ◽  
H. Zuo ◽  
K. Haines
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Barents Sea ◽  
Southern Oscillation ◽  
Similar Response ◽  
Enso Events ◽  
Ice Volume ◽  
The North ◽  
The Barents Sea ◽  
The North Atlantic

Abstract. An analysis of observational data in the Barents Sea along a meridian at 33°30' E between 70°30' and 72°30' N has reported a negative correlation between El Niño/La Niña Southern Oscillation (ENSO) events and water temperature in the top 200 m: the temperature drops about 0.5 °C during warm ENSO events while during cold ENSO events the top 200 m layer of the Barents Sea is warmer. Results from 1 and 1/4-degree global NEMO models show a similar response for the whole Barents Sea. During the strong warm ENSO event in 1997–1998 an anomalous anticyclonic atmospheric circulation over the Barents Sea enhances heat loses, as well as substantially influencing the Barents Sea inflow from the North Atlantic, via changes in ocean currents. Under normal conditions along the Scandinavian peninsula there is a warm current entering the Barents Sea from the North Atlantic, however after the 1997–1998 event this current is weakened. During 1997–1998 the model annual mean temperature in the Barents Sea is decreased by about 0.8 °C, also resulting in a higher sea ice volume. In contrast during the cold ENSO events in 1999–2000 and 2007–2008, the model shows a lower sea ice volume, and higher annual mean temperatures in the upper layer of the Barents Sea of about 0.7 °C. An analysis of model data shows that the strength of the Atlantic inflow in the Barents Sea is the main cause of heat content variability, and is forced by changing pressure and winds in the North Atlantic. However, surface heat-exchange with the atmosphere provides the means by which the Barents sea heat budget relaxes to normal in the subsequent year after the ENSO events.

scholarly journals Modeled and Observed Multidecadal Variability in the North Atlantic Jet Stream and Its Connection to Sea Surface Temperatures

2018 ◽  
Vol 31 (20) ◽  
pp. 8313-8338 ◽  
Author(s):  
Isla R. Simpson ◽  
Clara Deser ◽  
Karen A. McKinnon ◽  
Elizabeth A. Barnes
Keyword(s):  
North Atlantic ◽  
Sea Surface ◽  
Late Winter ◽  
Jet Stream ◽  
Sea Surface Temperatures ◽  
Multidecadal Variability ◽  
The North ◽  
Surface Temperatures ◽  
The North Atlantic ◽  
North Atlantic Jet

Multidecadal variability in the North Atlantic jet stream in general circulation models (GCMs) is compared with that in reanalysis products of the twentieth century. It is found that almost all models exhibit multidecadal jet stream variability that is entirely consistent with the sampling of white noise year-to-year atmospheric fluctuations. In the observed record, the variability displays a pronounced seasonality within the winter months, with greatly enhanced variability toward the late winter. This late winter variability exceeds that found in any GCM and greatly exceeds expectations from the sampling of atmospheric noise, motivating the need for an underlying explanation. The potential roles of both external forcings and internal coupled ocean–atmosphere processes are considered. While the late winter variability is not found to be closely connected with external forcing, it is found to be strongly related to the internally generated component of Atlantic multidecadal variability (AMV) in sea surface temperatures (SSTs). In fact, consideration of the seasonality of the jet stream variability within the winter months reveals that the AMV is far more strongly connected to jet stream variability during March than the early winter months or the winter season as a whole. Reasoning is put forward for why this connection likely represents a driving of the jet stream variability by the SSTs, although the dynamics involved remain to be understood. This analysis reveals a fundamental mismatch between late winter jet stream variability in observations and GCMs and a potential source of long-term predictability of the late winter Atlantic atmospheric circulation.

scholarly journals A Nonstationary ENSO–NAO Relationship Due to AMO Modulation

2018 ◽  
Vol 32 (1) ◽  
pp. 33-43 ◽  
Author(s):  
Wenjun Zhang ◽  
Xuebin Mei ◽  
Xin Geng ◽  
Andrew G. Turner ◽  
Fei-Fei Jin
Keyword(s):  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Circulation Model ◽  
La Niña ◽  
Late Winter ◽  
The North ◽  
La Nina ◽  
The North Atlantic

Abstract Many previous studies have demonstrated a high uncertainty in the relationship between El Niño–Southern Oscillation (ENSO) and the North Atlantic Oscillation (NAO). In the present work, decadal modulation by the Atlantic multidecadal oscillation (AMO) is investigated as a possible cause of the nonstationary ENSO–NAO relationship based on observed and reanalysis data. It is found that the negative ENSO–NAO correlation in late winter is significant only when ENSO and the AMO are in phase (AMO+/El Niño and AMO−/La Niña). However, no significant ENSO-driven atmospheric anomalies can be observed over the North Atlantic when ENSO and the AMO are out of phase (AMO−/El Niño and AMO+/La Niña). Further analysis indicates that the sea surface temperature anomaly (SSTA) in the tropical North Atlantic (TNA) plays an essential role in this modulating effect. Because of broadly analogous TNA SSTA responses to both ENSO and the AMO during late winter, a warm SSTA in the TNA is evident when El Niño occurs during a positive AMO phase, resulting in a significantly weakened NAO, and vice versa when La Niña occurs during a negative AMO phase. In contrast, neither the TNA SSTA nor the NAO shows a prominent change under out-of-phase combinations of ENSO and AMO. The AMO modulation and the associated effect of the TNA SSTA are shown to be well reproduced by historical simulations of the HadCM3 coupled model and further verified by forced experiments using an atmospheric circulation model. These offer hope that similar models will be able to make predictions for the NAO when appropriately initialized.

Dynamics of the ENSO Teleconnection and NAO Variability in the North Atlantic–European Late Winter

2020 ◽  
Vol 33 (3) ◽  
pp. 907-923 ◽  
Author(s):  
Bianca Mezzina ◽  
Javier García-Serrano ◽  
Ileana Bladé ◽  
Fred Kucharski
Keyword(s):  
North Atlantic ◽  
Southern Oscillation ◽  
Reanalysis Data ◽  
Late Winter ◽  
Sea Level Pressure ◽  
The North ◽  
Nao Index ◽  
Eddy Heat Flux ◽  
The North Atlantic ◽  
The North Atlantic Oscillation

AbstractThe winter extratropical teleconnection of El Niño–Southern Oscillation (ENSO) in the North Atlantic–European (NAE) sector remains controversial, concerning both the amplitude of its impacts and the underlying dynamics. However, a well-established response is a late-winter (January–March) signal in sea level pressure (SLP) consisting of a dipolar pattern that resembles the North Atlantic Oscillation (NAO). Clarifying the relationship between this “NAO-like” ENSO signal and the actual NAO is the focus of this study. The ENSO–NAE teleconnection and NAO signature are diagnosed by means of linear regression onto the sea surface temperature (SST) Niño-3.4 index and an EOF-based NAO index, respectively, using long-term reanalysis data (NOAA-20CR, ERA-20CR). While the similarity in SLP is evident, the analysis of anomalous upper-tropospheric geopotential height, zonal wind, and transient-eddy momentum flux, as well as precipitation and meridional eddy heat flux, suggests that there is no dynamical link between the phenomena. The observational results are further confirmed by analyzing two 10-member ensembles of atmosphere-only simulations (using an intermediate-complexity and a state-of-the-art model) with prescribed SSTs over the twentieth century. The SST-forced variability in the Northern Hemisphere is dominated by the extratropical ENSO teleconnection, which provides modest but significant SLP skill in the NAE midlatitudes. The regional internally generated variability, estimated from residuals around the ensemble mean, corresponds to the NAO pattern. It is concluded that distinct dynamics are at play in the ENSO–NAE teleconnection and NAO variability, and caution is advised when interpreting the former in terms of the latter.

scholarly journals Multicolony tracking reveals potential threats to little auks wintering in the North Atlantic from marine pollution and shrinking sea ice cover

2013 ◽  
Vol 19 (10) ◽  
pp. 1322-1332 ◽  
Author(s):  
Jérôme Fort ◽  
Børge Moe ◽  
Hallvard Strøm ◽  
David Grémillet ◽  
Jorg Welcker ◽  
...  
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Marine Pollution ◽  
Ice Cover ◽  
The North ◽  
The North Atlantic

scholarly journals Impact of a Reduced Arctic Sea Ice Cover on Ocean and Atmospheric Properties

2012 ◽  
Vol 25 (1) ◽  
pp. 307-319 ◽  
Author(s):  
Jan Sedláček ◽  
Reto Knutti ◽  
Olivia Martius ◽  
Urs Beyerle
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
Arctic Basin ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
Storm Tracks ◽  
The Arctic ◽  
The North ◽  
Arctic Sea ◽  
The North Atlantic

Abstract The Arctic sea ice cover declined over the last few decades and reached a record minimum in 2007, with a slight recovery thereafter. Inspired by this the authors investigate the response of atmospheric and oceanic properties to a 1-yr period of reduced sea ice cover. Two ensembles of equilibrium and transient simulations are produced with the Community Climate System Model. A sea ice change is induced through an albedo change of 1 yr. The sea ice area and thickness recover in both ensembles after 3 and 5 yr, respectively. The sea ice anomaly leads to changes in ocean temperature and salinity to a depth of about 200 m in the Arctic Basin. Further, the salinity and temperature changes in the surface layer trigger a “Great Salinity Anomaly” in the North Atlantic that takes roughly 8 yr to travel across the North Atlantic back to high latitudes. In the atmosphere the changes induced by the sea ice anomaly do not last as long as in the ocean. The response in the transient and equilibrium simulations, while similar overall, differs in specific regional and temporal details. The surface air temperature increases over the Arctic Basin and the anomaly extends through the whole atmospheric column, changing the geopotential height fields and thus the storm tracks. The patterns of warming and thus the position of the geopotential height changes vary in the two ensembles. While the equilibrium simulation shifts the storm tracks to the south over the eastern North Atlantic and Europe, the transient simulation shifts the storm tracks south over the western North Atlantic and North America. The authors propose that the overall reduction in sea ice cover is important for producing ocean anomalies; however, for atmospheric anomalies the regional location of the sea ice anomalies is more important. While observed trends in Arctic sea ice are large and exceed those simulated by comprehensive climate models, there is little evidence based on this particular model that the seasonal loss of sea ice (e.g., as occurred in 2007) would constitute a threshold after which the Arctic would exhibit nonlinear, irreversible, or strongly accelerated sea ice loss. Caution should be exerted when extrapolating short-term trends to future sea ice behavior.

scholarly journals A Hemispheric Mechanism for the Atlantic Multidecadal Oscillation

2007 ◽  
Vol 20 (11) ◽  
pp. 2706-2719 ◽  
Author(s):  
Mihai Dima ◽  
Gerrit Lohmann
Keyword(s):  
Sea Ice ◽  
North Atlantic ◽  
North Pacific ◽  
Thermohaline Circulation ◽  
Atlantic Multidecadal Oscillation ◽  
Sea Surface ◽  
The North ◽  
Sea Surface Temperature Anomalies ◽  
The North Atlantic ◽  
The North Pacific

Abstract The physical processes associated with the ∼70-yr period climate mode, known as the Atlantic multidecadal oscillation (AMO), are examined. Based on analyses of observational data, a deterministic mechanism relying on atmosphere–ocean–sea ice interactions is proposed for the AMO. Variations in the thermohaline circulation are reflected as uniform sea surface temperature anomalies in the North Atlantic. These anomalies are associated with a hemispheric wavenumber-1 sea level pressure (SLP) structure in the atmosphere that is amplified through atmosphere–ocean interactions in the North Pacific. The SLP pattern and its associated wind field affect the sea ice export through Fram Strait, the freshwater balance in the northern North Atlantic, and consequently the strength of the large-scale ocean circulation. It generates sea surface temperature anomalies with opposite signs in the North Atlantic and completes a negative feedback. The authors find that the time scale of the cycle is associated with the thermohaline circulation adjustment to freshwater forcing, the SST response to it, the oceanic adjustment in the North Pacific, and the sea ice response to the wind forcing. Finally, it is argued that the Great Salinity Anomaly in the late 1960s and 1970s is part of AMO.

scholarly journals An interannual link between Arctic sea-ice cover and the North Atlantic Oscillation

2017 ◽  
Vol 50 (1-2) ◽  
pp. 423-441 ◽  
Author(s):  
Mihaela Caian ◽  
Torben Koenigk ◽  
Ralf Döscher ◽  
Abhay Devasthale
Keyword(s):  
Sea Ice ◽  
North Atlantic Oscillation ◽  
North Atlantic ◽  
Ice Cover ◽  
Arctic Sea Ice ◽  
The North ◽  
Arctic Sea ◽  
The North Atlantic ◽  
The North Atlantic Oscillation
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