Changes in the probability of larvae crossing the North Atlantic during the 20th century

2019 ◽  
Vol 70 (8) ◽  
pp. 1150 ◽  
Author(s):  
Laura Rodríguez-Díaz ◽  
Inés Álvarez ◽  
Moncho Gómez-Gesteira ◽  
Fran Santos
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Gulf Stream ◽  
North Atlantic Ocean ◽  
Past Century ◽  
Straits Of Florida ◽  
The North ◽  
Ocean Data Assimilation ◽  
The North Atlantic ◽  
Passive Tracers

Lagrangian trajectories of passive particles were simulated using velocity fields provided by the Simple Ocean Data Assimilation model to determine changes in their probability of crossing the North Atlantic Ocean during the period 1899–2010. Particles were released in the Straits of Florida, where the Gulf Stream is the main driving force. The results showed that eddy kinetic energy increased along the Gulf Stream path, which enhanced connectivity across the Atlantic. The time for water parcels (passive tracers) to cross the North Atlantic Ocean has shortened in the past century, with a minimum crossing period of 6–7 months and a decreasing trend ranging from –0.15 to –0.40 months per decade.

scholarly journals Assessment of an ensemble system that assimilates Jason-1/Envisat altimeter data in a probabilistic model of the North Atlantic ocean circulation

Ocean Science ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 425-438 ◽  
Author(s):  
G. Candille ◽  
J.-M. Brankart ◽  
P. Brasseur
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Gulf Stream ◽  
North Atlantic Ocean ◽  
Altimeter Data ◽  
Stochastic Perturbations ◽  
The North ◽  
Altimetric Data ◽  
The North Atlantic ◽  
Along Track

Abstract. A realistic circulation model of the North Atlantic ocean at 0.25° resolution (NATL025 NEMO configuration) has been adapted to explicitly simulate model uncertainties. This is achieved by introducing stochastic perturbations in the equation of state to represent the effect of unresolved scales on the model dynamics. The main motivation for this work is to develop ensemble data assimilation methods, assimilating altimetric data from past missions Jason-1 and Envisat. The assimilation experiment is designed to provide a description of the uncertainty associated with the Gulf Stream circulation for years 2005/2006, focusing on frontal regions which are predominantly affected by unresolved dynamical scales. An ensemble based on such stochastic perturbations is first produced and evaluated using along-track altimetry observations. Then each ensemble member is updated by a square root algorithm based on the SEEK (singular evolutive extended Kalman) filter (Brasseur and Verron, 2006). These three elements – stochastic parameterization, ensemble simulation and 4-D observation operator – are then used together to perform a 4-D analysis of along-track altimetry over 10-day windows. Finally, the results of this experiment are objectively evaluated using the standard probabilistic approach developed for meteorological applications (Toth et al., 2003; Candille et al., 2007). The results show that the free ensemble – before starting the assimilation process – correctly reproduces the statistical variability over the Gulf Stream area: the system is then pretty reliable but not informative (null probabilistic resolution). Updating the free ensemble with altimetric data leads to a better reliability with an information gain of around 30% (for 10-day forecasts of the SSH variable). Diagnoses on fully independent data (i.e. data that are not assimilated, like temperature and salinity profiles) provide more contrasted results when the free and updated ensembles are compared.

On the North Atlantic Ocean Heat Content Change between 1955–70 and 1980–95

2012 ◽  
Vol 25 (10) ◽  
pp. 3619-3628 ◽  
Author(s):  
Xiaoming Zhai ◽  
Luke Sheldon
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Gulf Stream ◽  
Large Scale ◽  
North Atlantic Ocean ◽  
Heat Content ◽  
Ocean Heat Content ◽  
The North ◽  
Content Change ◽  
The North Atlantic

Abstract The upper-ocean heat content of the North Atlantic has undergone significant changes over the last 50 years but the underlying physical mechanisms are not yet well understood. In the present study, the authors examine the North Atlantic ocean heat content change in the upper 700 m between the 1955–70 and 1980–95 periods. Consistent with previous studies, the large-scale pattern consists of warming of the tropics and subtropics and cooling of the subpolar ocean. However, this study finds that the most significant heat content change in the North Atlantic during these two time periods is the warming of the Gulf Stream region. Numerical experiments strongly suggest that this warming in the Gulf Stream region is largely driven by changes of the large-scale wind forcing. Furthermore, the increased ocean heat content in the Gulf Stream region appears to feedback on to the atmosphere, resulting in warmer surface air temperature and enhanced precipitation there.

scholarly journals III. The circulation of the surface waters of the north atlantic ocean

1901 ◽  
Vol 196 (274-286) ◽  
pp. 61-203 ◽  
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Surface Waters ◽  
Gulf Stream ◽  
North Atlantic Ocean ◽  
Critical Examination ◽  
Northern Latitude ◽  
The North ◽  
History Of ◽  
The North Atlantic

The history of our knowledge of the currents of the North Atlantic Ocean up to the year 1870 has been written once for all by Petermann (I), who in that year published a memoir maintaining, contrary to the opinion of Findlay, Blunt, and Carpenter, that eastern and northern extensions of the Gulf Stream were the prime factors in the circulation. Petermann subjected practically the whole of the material in the way of observations then extant to an exhaustive critical examination, and came to conclusions which are worth quoting, in the summary, inasmuch as the observations of the twenty succeeding years did not seriously modify them :— 1. The hot source and core of the Gulf Stream extends from the Strait of Florida, along the North American coast at all times.... up to the 37th degree of northern latitude.

Heightened tropical cyclone activity in the North Atlantic: natural variability or climate trend?

2007 ◽  
Vol 365 (1860) ◽  
pp. 2695-2716 ◽  
Author(s):  
Greg J Holland ◽  
Peter J Webster
Keyword(s):  
Tropical Cyclone ◽  
Atlantic Ocean ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Past Century ◽  
Peak Period ◽  
Climate Trend ◽  
The North ◽  
Major Hurricane ◽  
The North Atlantic

We find that long-period variations in tropical cyclone and hurricane frequency over the past century in the North Atlantic Ocean have occurred as three relatively stable regimes separated by sharp transitions. Each regime has seen 50% more cyclones and hurricanes than the previous regime and is associated with a distinct range of sea surface temperatures (SSTs) in the eastern Atlantic Ocean. Overall, there appears to have been a substantial 100-year trend leading to related increases of over 0.7°C in SST and over 100% in tropical cyclone and hurricane numbers. It is concluded that the overall trend in SSTs, and tropical cyclone and hurricane numbers is substantially influenced by greenhouse warming. Superimposed on the evolving tropical cyclone and hurricane climatology is a completely independent oscillation manifested in the proportions of tropical cyclones that become major and minor hurricanes. This characteristic has no distinguishable net trend and appears to be associated with concomitant variations in the proportion of equatorial and higher latitude hurricane developments, perhaps arising from internal oscillations of the climate system. The period of enhanced major hurricane activity during 1945–1964 is consistent with a peak period in major hurricane proportions.

scholarly journals Assessment of an ensemble system that assimilates Jason-1/Envisat altimeter data in a probabilistic model of the North Atlantic ocean circulation

2014 ◽  
Vol 11 (6) ◽  
pp. 2647-2690 ◽  
Author(s):  
G. Candille ◽  
J. M. Brankart ◽  
P. Brasseur
Keyword(s):  
Atlantic Ocean ◽  
North Atlantic ◽  
Gulf Stream ◽  
North Atlantic Ocean ◽  
Altimeter Data ◽  
Stochastic Perturbations ◽  
The North ◽  
Altimetric Data ◽  
The North Atlantic ◽  
Along Track

Abstract. A realistic circulation model of the North Atlantic ocean at 1/4° resolution (NATL025 NEMO configuration) has been adapted to explicitly simulate model uncertainties. This is achieved by introducing stochastic perturbations in the equation of state to represent the effect of unresolved scales on the model dynamics. The main motivation for this work is to develop ensemble data assimilation methods, assimilating altimetric data from past missions JASON-1 and ENVISAT. The assimilation experiment is designed to better control the Gulf Stream circulation for years 2005/06, focusing on frontal regions which are predominantly affected by unresolved dynamical scales. An ensemble based on such stochastic perturbations is first produced and evaluated using along-track altimetry observations. The Incremental Analysis Update (IAU) scheme is applied in order to obtain an ensemble of continuous trajectories all over the 2005/06 assimilation period. These three elements – stochastic parameterization, ensemble simulation and 4-D observation operator – are then used together to perform a 4-D analysis of along-track altimetry over 10 day windows. Finally, the results of this experiment are objectively evaluated using the standard probabilistic approach developed for meteorological applications (Toth et al., 2003; Candille et al., 2007). The results show that the free ensemble – before starting the assimilation process – correctly reproduces the statistical variability over the Gulf Stream area: the system is then pretty reliable but not informative (null probabilistic resolution). Updating the free ensemble with altimetric data leads to a better reliability with an information gain around 30% (for 10 day forecasts of the SSH variable). Diagnoses on fully independent data (i.e. data that are not assimilated, like temperature and salinity profiles) provide more contrasted results when the free and updated ensembles are compared.

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