North Atlantic currents The Portugal Current is a weak ocean current that flows south along the coast of

Portugal Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring Cabo da Roca, the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it share ...

and the

Iberian Peninsula The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...

. Some publications define this current as part of the

Canary Current The Canary Current is a wind-driven surface current that is part of the North Atlantic Gyre. This eastern boundary current branches south from the North Atlantic Current and flows southwest about as far as Senegal where it turns west and later jo ...

, while others distinguish it as a separate current. The Portugal Current system is supplied mainly by the intergyre zone in the Atlantic, a region of weak circulation between the

North Atlantic Current The North Atlantic Current (NAC), also known as North Atlantic Drift and North Atlantic Sea Movement, is a powerful warm western boundary current within the Atlantic Ocean that extends the Gulf Stream northeastward. Characteristics The NAC ...

to the north and the

Azores Current The Azores Current is a generally eastward to southeastward-flowing ocean current in the North Atlantic Ocean. It originates near the Grand Banks of Newfoundland where the Gulf Stream The Gulf Stream is a warm and swift Atlantic ocean cu ...

to the south. It is estimated, on average, to extend about 300 km beyond the shelf. It is also influenced by the more dominant neighboring Canary and

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

Currents, marking the northern extent of the Canary current. Other significant influences include seasonal winds, freshwater runoff from the Iberian Peninsula, the bottom topography found along the continental shelf break and slope, and the three main underlying water masses that are found below the seasonally variable surface layer. General water temperatures are between , depending on whether

upwelling Upwelling is an physical oceanography, oceanographic phenomenon that involves wind-driven motion of dense, cooler, and usually nutrient-rich water from deep water towards the ocean surface. It replaces the warmer and usually nutrient-depleted sur ...

(cooler water) or downwelling (warmer waters) dominates, though

sea surface temperature Sea surface temperature (or ocean surface temperature) is the ocean temperature, temperature of ocean water close to the surface. The exact meaning of ''surface'' varies in the literature and in practice. It is usually between and below the sea ...

s on the shelf have been observed to reach up to in the summer and remain between in the winter. Meddies (

eddies In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. Fluid ...

composed of

Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...

water) are also present, particularly in the region of the Tagus Abyssal Plain (about 11-13°W; 37-39°N) and along the shelf break and also occur in some Portuguese capes: Portimão Canyon, Cape St. Vincent, Estremadura Promontory and

Cape Finisterre Cape Finisterre (, also ; ; ) is a rock-bound peninsula on the west coast of Galicia, Spain. In Roman times it was believed to be an end of the known world. The name Finisterre, like that of Finistère in France, derives from the Latin , mean ...

, although some appear to come from the Espinho slope. Upwelling conditions are favourable from the beginning of April to the end of September (peaking in July and averaging 188 days) and downwelling from the beginning of October to the end of March (averaging 177 days), particularly January and February, due to dominant wind stress along the Iberian margin, although upwelling can occasionally occur in downwelling-favourable months and vice versa, mainly due to wind variability.

Concerns about climate change

From 1941 onwards, sea surface temperature offshore Portugal has been observed to rise > 0.01 °C per year. This trend has put some seaweed species, such as ''

Laminaria hyperborea ''Laminaria hyperborea'' is a species of large brown alga, a kelp in the family Laminariaceae, also known by the common names of tangle and cuvie. It is found in the sublittoral zone of the northern Atlantic Ocean. A variety, ''Laminaria hyperb ...

'', a kelp with an affinity for cooler water, with its distribution shifted northwards. It had its southern distribution limit at Peniche in the 1970s and 1980s, but is now only limited to waters off northern Portugal, providing further support to the notion of a reduction of

kelp forest Kelp forests are underwater areas with a high density of kelp, which covers a large part of the world's coastlines. Smaller areas of anchored kelp are called kelp beds. They are recognized as one of the most productive and dynamic ecosystems on E ...

s along the Iberian Peninsula. This increase in temperature is correlated with the decrease in the intensity of upwelling events from 1941 onwards, reducing the input of nutrient-enriched waters into the coast. Warm water species are colonizing new areas northwards while cold water species are shifting polewards, like the rustic limpet ('' Patella rustica'').

References

External links

* Currents of the Atlantic Ocean {{Marine-current-stub