Whilst a vineyards altitude is regularly touted on the technical sheet of its resulting wine it is extremely rare to see that particular vineyards altitude appear on the bottle itself. However, there is one wine region where this is not only not the case but in fact the opposite is true: Argentina. It is commonplace to flaunt a vineyards altitude in plain sight on a bottle of Argentinian Malbec with producers competing to show that they work with the highest-altitude vineyards. So why exactly is Argentinian Malbec grown at such high-altitude?
Whilst there is a large body of ongoing research aiming to better understand the effects of high-altitude vineyards on grape development, as it stands there are a couple of widely accepted benefits of high-altitude vineyards in warm climates and these are; diurnal temperature variation, overall temperature and sunlight exposure. I will further discuss each of the aforementioned benefits in order of above appearance.
Before we dive a little deeper in to the topic of diurnal temperature variation it is important to ensure that readers are somewhat aware of how a grape develops through its period of ripening; in particular how acidity and sugar levels develop.
As the vines reach veraison (a period of ripening) levels of acidity in the grapes are relatively high (around 20g/l) whilst sugar levels are relatively low. As the grapes ripen, and harvest approaches, through the process of respiration (cellular) the vine metabolises malic acid and as a byproduct of photosynthesis produces sucrose. Both sugar levels and acidity are crucial in determining a wines character; whilst acidity provides structure to wine and is pivotal in determining a wines ageing potential sugar plays a fundamental role in fermentation and determining the flavour profile of a finished wine.
Given what we know about the ripening period intuition tells us that grapes from warm climates (closer to the equator) tend to have low acidity, high sugar levels and produce wines with a relatively high ABV whereas grapes from cool climates (further from the equator) tend to have high acidity, low sugar levels and a relatively low ABV. But as with almost all things wine related, balance is central to producing good wine. In excessively warm climates (like Argentina) resulting wines can be intrusively high in alcohol and lack the necessary acidity to give structure and ‘zing’ to the wine, this is where high altitude vineyards come in to play.
A few things happen as you climb in altitude, one of these things is that the atmosphere becomes thinner. This means that as warm air rises in the atmosphere it goes through a period of expansion (from a dense atmosphere to a relatively sparse one) and during this period of expansion the heat content reduces and thus, the temperature falls. This reduced temperature allows for a more balanced ripening period where acid metabolism is not so rapid that the resulting wine is flabby and without structure.
This reduction in temperature at altitude allows grapes to be grown in warm climate regions closer to the equator without rapid acid metabolism and scorched grapes resulting in poor flavour profile in the end product. Further to this reduction in temperature a greater diurnal temperature variation at altitude adds great value by putting a stop to ripening at night therefore extending the ripening period and producing a Malbec altogether different to that of its European expression.
Simply put, diurnal temperature variation is the difference between the temperature in the day and temperature at night. This variation is greater at altitude because as the atmospheric pressure (and density) reduces as altitude increases, the atmospheres ability to store heat reduces. This means that as the sun goes down in the evening the temperature quickly falls and both photosynthesis and respiration are halted preventing metabolism of malic acid and allowing a more balanced development throughout the ripening period.
Further to reduced temperature and increased diurnal temperature variation there is an additional benefit to high-altitude vineyards and this is sunlight exposure. As altitude increases, the atmosphere becomes thinner. This means that the barrier between the sun and the earth’s surface is thinner, this causes an increase in sunlight intensity. At high altitude, ultraviolet-B light (UV-B, the most energetic fraction from sunlight) also increases. Since UV-B light is very strong at high altitude, it can damage living tissue. The plant defends itself against UV-B by producing certain components that are actually beneficial for grape quality. In fact, Mendoza’s wine growing regions planted above 1000 m asl tend to develop higher quality berries due to the increased levels of UV-B. The UV-B results in a greater accumulation of polyphenols and aromatic compounds in the berry, caused by the plant’s defence mechanism against sunlight; a thicker skin. A higher content of polyphenols and aromatics translates into a wine with a darker color, more complex flavors and longer aging potential.
I hope you have found this article useful and if you have any comments, questions or additions please do not hesitate to comment.