The Argentine Northwest (, NOA) is a geographic and historical region of Argentina comprising the provinces of Catamarca, Jujuy, La Rioja, Salta, Santiago del Estero and Tucumán. It borders Bolivia to the north, Chile to the west, the Northeast region to the east, the Center region to the south, and the Cuyo region to the southwest.
The region extends primarily over the Andes Mountains and their adjacent valleys, encompassing a diverse range of landscapes. The region's main geographic features are the Puna, the Calchaquí Valleys, the Yungas, and the Argentine portion of the Chaco Plains. Major rivers in the region include the Bermejo River, the Salí-Dulce River, and the Pilcomayo River.
According to INDEC (National Institute of Statistics and Censuses), the combined population of the provinces in 2022 was 5,859,115. San Miguel de Tucumán is the most populous city in the Argentine Northwest. Other significant cities include Salta, San Salvador de Jujuy and Santiago del Estero.
The region's economy is based on agriculture (especially sugarcane, tobacco, grapes, and citrus production), mining, tourism, and to a lesser extent, industry. Its strategic location makes it an important corridor for trade with Bolivia and Chile.
The region has a rich pre-Columbian history and was among the first areas colonized in what is now the Argentine territory. It was the site of some of the earliest cities founded, and during the colonial era, its strategic location made it an important transit and supply center for the regional economy under Spanish rule. Major battles and events during the Argentine War of Independence took place in the Northwest, including the Declaration of Independence in Tucumán in 1816.
The Argentine Northwest faces socioeconomic challenges as a historically underdeveloped region compared to more developed areas of the country. Nonetheless, it remains a vital cultural and tourism center within Argentina. The region has made notable contributions to the nation's identity, especially through its rich traditions in music, folklore, and gastronomy. Its distinctive identity is deeply rooted in a blend of indigenous and Spanish influences.
Geography
The Argentine Northwest comprises very distinct biomes, or geographical and climatic regions. From west to east they are:
The Altiplano or "Puna" High Mountains of the Andes Fertile valleys Red-rock canyons and mountain passes Humid Sub-Andean Sierras Tropical jungles or Yungas And the ecotone—or transitional zone—between the Yungas and the Chaco region.
Besides the Yungas jungle on the eastern fringe of the region, the only fertile lands are those near the river basins, which have been irrigated extensively. Across millennia the erosive forces of these rivers has gradually created a multitude of red-rock canyons, such as the Quebrada de Humahuaca and the Valles Calchaquíes.
West of these valleys the peaks of the Andes reach heights of over and the Altiplano, an extensive 3,500-meter high plateau, dominates the landscape and continues far north into Bolive and Southern Peru.
History
Archaeological finds In February 2021, archaeologists from the University of Buenos Aires–National Scientific and Technical Research Council announced the discovery of 12 graves dated to 6,000-1,300 years ago. Researchers also revealed necklaces and pendants next to some of the bodies. According to archaeologist Leticia Cortés, there were many kinds of burial methods, in individual or collective graves, and also in the posture of the bodies. Some were hyperflexed, like squatting, with the shoulders touching the knees.
Spanish colonization
Climate
Northwest Argentina is predominantly dry and hot and classified as subtropical. Owing to its rugged topography, the region is climatically diverse, depending on the elevation, temperature and distribution of precipitation. Consequentially, the vegetation will differ at these different climate types. In general, the climate can be divided into 2 main types: a cold arid or semi-arid climate at the higher elevations and warmer subtropical climate in the eastern parts of the region. Under the Köppen climate classification, the region has 5 different climate types which are semi–arid (BS), arid (BW), temperate climate without a dry season and with a dry season (Cf and CW respectively) and an alpine climate at the highest elevations.
The atmospheric circulation is controlled by the two semi–permanent South Atlantic and South Pacific highs, and a seasonal low-pressure system east of the Andes (called the Chaco Low). During summer, the interaction between the South Atlantic high and the Chaco low causes the low-pressure system to bring northeasterly and easterly winds that carry moisture to the region, particularly in the northern parts. The movement of moist air into the region during the summer results in very high precipitation. Most of the moisture comes from the east since the Andes block any moisture from the Pacific Ocean. Cold fronts that travel northwards to the region can produce precipitation during the summer months and is more prominent in the southern parts of the region. For example, in Tucumán Province, these cold fronts are responsible for 70% of the rainfall in that province. In contrast, during the winter months, the Chaco low attracts air masses from the South Pacific high, creating a dry and cold wind. This effect is more prominent in the winter months, when the intensity of the cold is more stronger. The Intertropical Convergence Zone reaches the region during the summer months, leading to low pressure, and unstable air masses due to the relatively high land temperatures compared to the sea during this season. This leads to enhanced precipitation in the form of convective thunderstorms during the summer months. During the winter months, the Intertropical Convergence Zone moves northwards to Ecuador while both the South Pacific and South Atlantic high move northwards, and the Chaco low weakens, all of which result in the suppression of rain during the winter. With the predominant wind being from the west and the Andes blocking most rain bearing clouds from the Pacific Ocean along with atmospheric circulation patterns unfavourable for rain, this results in a dry season during winter. At the highest elevations, westerly winds from the Pacific Ocean can penetrate during the winter months, leading to snowstorms.
Precipitation
Precipitation in the region is highly seasonal and is mostly concentrated in the summer months, during which precipitation decreases from east to west. Precipitation is distributed irregularly owing to relief. As moist air reaches the eastern slopes of the mountains, this moist air raises up vertically, cooling adiabatically, leading to the formation of clouds which generate copious amounts of rain. The eastern slopes of the mountains can receive between of precipitation a year although some places can receive of precipitation per year owing to orographic precipitation. In the south, the orographic effect is enhanced by advancing cold fronts from the south, resulting in enhanced precipitation. The high rainfall on these first slopes creates a thick jungle that extends in a narrow strip along these ranges. Beyond the first slopes of the Andes into the valleys, the air descends vertically, warming adiabatically, creating air that is drier and warmer than on the eastern slopes. Since the mountain ranges are oriented in a north–south direction, increase in elevation to the west, and have a discontinuous orography, this allows valleys to have regions of relatively high precipitation in the west and drier regions in eastern parts of the valleys through orographic precipitation.
In the temperate valleys, which include major cities such as Salta and Jujuy, average precipitation ranges from . For example, in the Lerma Valley which is surrounded by tall mountains (only the northeastern part of the valley is surrounded by shorter mountains), precipitation ranges from in Salta to in San Lorenzo, just away. Rainfall in the Lerma valley in Salta and in wetter valleys in Jujuy province, including its provincial capital, is mainly concentrated in the summer months and falls in short but heavy bursts.
Valleys in the southern parts of the region are drier than northern valleys due to the mountains on the eastern slopes of both the Andes and the Sierras Pampeanas being taller than the ones in the north (ranging from ), presenting a significant orographic barrier that blocks moist winds from the Atlantic and Pacific oceans. These valleys often receive less than of precipitation per year and are characterized by sparse vegetation adapted to the arid climate. For example, in La Rioja Province, mean annual precipitation ranges from in the easternmost parts to at the foot of the Andes. Similarly in Catamarca Province, the mean annual precipitation varies from in the middle of valleys between the Andes mountains to more than in the nearby mountain ranges which form the valleys. In Jujuy province, precipitation in the dry Quebrada de Humahuaca valley ranges from . A similar annual precipitation is found in the dry Calchaquí Valleys, with mean annual precipitation ranging from in Molinos to in Cafayate. Further west in the Puna region next to Bolivia, the average elevation is and the terrain is mostly desert due to the higher elevations of the mountains on the east from both the Andes and the northwest extension of the Sierras Pampeanas, blocking most of the easterly winds from coming in.
Precipitation in the Puna region averages less than a year while potential evapotranspiration ranges from a year, owing to the high insolation, strong winds, and low humidity that exacerbates the dry conditions. Owing to the low precipitation in conjunction with the extreme climatic conditions, the Puna region has a water deficit in all months of the year. Although easterly winds are rare in the Puna region, they bring 88–96% of the precipitation to the area. Snowfall is rare, averaging less than 5 days of snow per year since most of the precipitation falls in the summer in the form of rain. The southeast part of the Puna region is very arid and receives the lowest annual precipitation in the region, averaging . In the northeast part of the Puna region in Jujuy Province, mean annual precipitation ranges from . Due to the aridity of these mountains at high elevations, the snowline can extend as far up as 6,000 m above sea level. The El Niño Southern Oscillation influences precipitation levels in northwest Argentina. During an El Niño year, the westerly flow is strengthened while moisture content from the east is reduced, resulting in a drier rainy season. In contrast, during a La Niña year, there is enhanced easterly moisture transport, resulting in a more intense rainy season. Nonetheless, this trend is highly variable both spatially and temporally.
Temperatures
Temperatures in northwest Argentina vary with elevation. In the temperate valleys which includes the cities of Salta and Jujuy, they have a temperate climate, with mild temperatures in the summer (a mean of in Salta, in Jujuy in January) and extremely dry and cool winters with regular frosts (a mean of in Salta and in Jujuy in July). The diurnal range in these cities is fairly large, particularly in the winter.