scholarly journals Persistent Atmospheric and Oceanic Anomalies in the North Atlantic from Summer 2009 to Summer 2010

2011 ◽  
Vol 24 (22) ◽  
pp. 5812-5830 ◽  
Author(s):  
Zeng-Zhen Hu ◽  
Arun Kumar ◽  
Bohua Huang ◽  
Yan Xue ◽  
Wanqiu Wang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
Negative Phase ◽  
Atlantic Basin ◽  
Term Trend ◽  
The North ◽  
The North Atlantic ◽  
Long Term Trend

Abstract In this work, the authors analyze the air–sea interaction processes associated with the persistent atmospheric and oceanic anomalies in the North Atlantic Ocean during summer 2009–summer 2010 with a record-breaking positive sea surface temperature anomaly (SSTA) in the hurricane Main Development Region (MDR) in the spring and summer of 2010. Contributions to the anomalies from the El Niño–Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), and a long-term trend are identified. The warming in the tropical North Atlantic during summer 2009–summer 2010 represented a typical response to ENSO, preconditioned and amplified by the influence of a strong and persistent negative phase of the NAO. The long-term trends enhanced the warming in the high and low latitudes and weakened the cooling in the midlatitudes. The persistent negative phase of the NAO was associated with active thermodynamic air–sea interaction in the North Atlantic basin. Surface wind anomalies associated with the NAO altered the ocean surface heat flux and changed the SSTA, which was likely further enhanced by the positive wind speed–evaporation–SST feedback. The total heat flux was dominated by the latent and sensible heat fluxes, while the shortwave radiation contributed to the tropical SSTA to a lesser degree. Sensitivity experiments with an atmospheric general circulation model forced by observed SST in the Atlantic Ocean alone suggested that the Atlantic SSTA, which was partly forced by the NAO, had some positive contribution to the persistence of the negative phase of the NAO. Therefore, the persistent NAO condition is partly an outcome of the global climate anomalies and the ocean–atmosphere feedback within the Atlantic basin. The combination of the ENSO, NAO, and long-term trend resulted in the record-breaking positive SSTA in the MDR in the boreal spring and summer of 2010. On the basis of the statistical relationship, the SSTA pattern in the North Atlantic was reasonably well predicted by using the preceding ENSO and NAO as predictors.

scholarly journals Reduction in Ocean Heat Transport at 26°N since 2008 Cools the Eastern Subpolar Gyre of the North Atlantic Ocean

2020 ◽  
Vol 33 (5) ◽  
pp. 1677-1689 ◽  
Author(s):  
Harry L. Bryden ◽  
William E. Johns ◽  
Brian A. King ◽  
Gerard McCarthy ◽  
Elaine L. McDonagh ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Heat Transport ◽  
North Atlantic ◽  
Ocean Heat Transport ◽  
North Atlantic Current ◽  
The North ◽  
Heat Uptake ◽  
The North Atlantic ◽  
Atlantic Current

AbstractNorthward ocean heat transport at 26°N in the Atlantic Ocean has been measured since 2004. The ocean heat transport is large—approximately 1.25 PW, and on interannual time scales it exhibits surprisingly large temporal variability. There has been a long-term reduction in ocean heat transport of 0.17 PW from 1.32 PW before 2009 to 1.15 PW after 2009 (2009–16) on an annual average basis associated with a 2.5-Sv (1 Sv ≡ 106 m3 s−1) drop in the Atlantic meridional overturning circulation (AMOC). The reduction in the AMOC has cooled and freshened the upper ocean north of 26°N over an area following the offshore edge of the Gulf Stream/North Atlantic Current from the Bahamas to Iceland. Cooling peaks south of Iceland where surface temperatures are as much as 2°C cooler in 2016 than they were in 2008. Heat uptake by the atmosphere appears to have been affected particularly along the path of the North Atlantic Current. For the reduction in ocean heat transport, changes in ocean heat content account for about one-quarter of the long-term reduction in ocean heat transport while reduced heat uptake by the atmosphere appears to account for the remainder of the change in ocean heat transport.

Thirty Years of Atmospheric Extinction from Telescopes of the North Atlantic Canary Archipelago

2015 ◽  
Vol 29 (1) ◽  
pp. 227-240 ◽  
Author(s):  
Benjamin A. Laken ◽  
Hannu Parviainen ◽  
Alejandro García-Gil ◽  
Casiana Muñoz-Tuñón ◽  
Antonia M. Varela ◽  
...  
Keyword(s):  
North Atlantic ◽  
Mixture Distributions ◽  
Solar Telescope ◽  
Atmospheric Extinction ◽  
The North ◽  
The North Atlantic ◽  
Volcanic Aerosols ◽  
Low Amplitude ◽  
Long Term Trend

Abstract This study examines 30 years of atmospheric extinction, τ, obtained from both stellar and solar telescope measurements, at ~2.4 km MSL, from the North Atlantic Canary Archipelago—an island chain located at approximately 28°N, around 100 km from the west coast of Africa. Data from three AERONET monitors, located at varying heights on one of the main islands, were also used, although these are only available over a shorter (<10 yr) period. The Canary Archipelago is regularly affected by dust intrusions into the local atmosphere as they intersect one of the primary export pathways of mineral dust from the Sahara. The τ of “baseline” and “dust influenced” conditions were statistically distinguished by fitting normal-gamma mixture distributions to the observations using Markov chain Monte Carlo methods, and then the seasonal and long-term characteristics of these data were examined. The telescope data show that baseline conditions are usually stable at τ < 0.1 (except during periods influenced by volcanic aerosols) and indicate the existence of a low-amplitude () seasonal variation. During dust-influenced conditions, τ regularly reaches values of a factor of 2–6 times higher than normal. The majority of dust intrusions take place during the months of July and August, when they may occur 44 ± 15% of the time, predominantly at high altitudes (with ~94.3 ± 1.6% of intrusions occurring ≥ 2.4 km), whereas during the months of November–May, dust intrusions occur far less frequently (~19 ± 7%) and are more common at lower altitudes—with intrusions at <2.4 km comprising ~ 79.5 ± 3.2% of all outbreaks. Year-to-year variations in the frequency of dust-influenced conditions (of ~9%) were found but no long-term trend over the observed 30-yr period.

scholarly journals A model study of the seasonal and long–term North Atlantic surface <i>p</i>CO<sub>2</sub> variability

2012 ◽  
Vol 9 (3) ◽  
pp. 907-923 ◽  
Author(s):  
J. F. Tjiputra ◽  
A. Olsen ◽  
K. Assmann ◽  
B. Pfeil ◽  
C. Heinze
Keyword(s):  
Heat Flux ◽  
Ocean Circulation ◽  
North Atlantic ◽  
Dissolved Inorganic Carbon ◽  
Ocean Model ◽  
Surface Ocean ◽  
The North ◽  
Increasing Trend ◽  
The North Atlantic

Abstract. A coupled biogeochemical-physical ocean model is used to study the seasonal and long–term variations of surface pCO2 in the North Atlantic Ocean. The model agrees well with recent underway pCO2 observations from the Surface Ocean CO2 Atlas (SOCAT) in various locations in the North Atlantic. Some of the distinct seasonal cycles observed in different parts of the North Atlantic are well reproduced by the model. In most regions except the subpolar domain, recent observed trends in pCO2 and air–sea carbon fluxes are also simulated by the model. Over the longer period between 1960–2008, the primary mode of surface pCO2 variability is dominated by the increasing trend associated with the invasion of anthropogenic CO2 into the ocean. We show that the spatial variability of this dominant increasing trend, to first order, can be explained by the surface ocean circulation and air–sea heat flux patterns. Regions with large surface mass transport and negative air–sea heat flux have the tendency to maintain lower surface pCO2. Regions of surface convergence and mean positive air–sea heat flux such as the subtropical gyre and the western subpolar gyre have a higher long–term surface pCO2 mean. The North Atlantic Oscillation (NAO) plays a major role in controlling the variability occurring at interannual to decadal time scales. The NAO predominantly influences surface pCO2 in the North Atlantic by changing the physical properties of the North Atlantic water masses, particularly by perturbing the temperature and dissolved inorganic carbon in the surface ocean. We show that present underway sea surface pCO2 observations are valuable for both calibrating the model, as well as for improving our understanding of the regionally heterogeneous variability of surface pCO2. In addition, they can be important for detecting any long term change in the regional carbon cycle due to ongoing climate change.

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