Researchers determine the causes of the acute drought that affected the Pantanal

Publicado em 25 maio 2021

The acute drought suffered by the Pantanal in 2019-20, thought-about the worst within the final 50 years, was attributable to pure local weather circumstances just like these underlying the 2014-16 water disaster in São Paulo state. The Pantanal is likely one of the world’s largest wetlands. The Brazilian portion is situated within the Heart-West area, primarily Mato Grosso do Sul state.

The 2019-20 excessive drought was studied by researchers affiliated with the Pure Catastrophe Surveillance and Early Warning Heart (CEMADEN), the Nationwide Area Analysis Institute (INPE) and São Paulo State College (UNESP) as a part of a mission supported by FAPESP beneath the aegis of its Analysis Program on World Local weather Change (RPGCC).

The outcomes of the examine are printed within the journal Frontiers in Water.

“The latest drought within the Pantanal was attributable to a meteorological phenomenon we name atmospheric blocking. A high-pressure space prevented the formation of rainclouds all through the central-western portion of South America. Temperatures had been very excessive and relative humidity very low,” José Marengo, a researcher at CEMADEN and principal investigator for the examine, instructed Agência FAPESP.

“Lack of rain mixed with excessive temperatures and really low humidity led to a heightened danger of fireplace, which prolonged to agricultural areas in addition to pure elements of the biome.”

Deliberate burning of vegetation to clear land for cattle ranching contributed to the unfold of wildfires all through the area, and these had been tougher to regulate owing to the lengthy interval of drought. “Fires precipitated on one hand by hotter air and lack of rain within the Pantanal, and on the opposite by the burning of areas to clear the vegetation for cattle to graze, resulted in environmental catastrophe,” Marengo stated.

Sources of observational information

To analyze the hydroclimatic causes of drought within the Pantanal, the researchers used an array of sources of observational hydrological information (on the extent of the Paraguay River) in addition to information on rainfall and hydroclimatic teleconnections (hyperlinks between hydrological occasions and atmospheric circulation patterns inflicting climate phenomena). In addition they used data on land use and distant sensing information to characterize water stress and drought within the Pantanal.

Based mostly on an evaluation of all these datasets they had been capable of present a transparent description of the interannual variability of rainfall, river streamflow, and drought-related elements, concluding that the drought was attributable to a posh mixture of hydroclimatic teleconnections.

“The shortage of rain through the summer time in 2019 and 2020 within the Pantanal was as a consequence of a lower within the movement of heat humid air from the Amazon,” Marengo stated.

A part of the rain that falls on the Pantanal is introduced by winds blowing from the North Atlantic to the Amazon, and from there to the Pantanal in Brazil’s Heart-West area. The humidity coming down from the Amazon and chilly fronts developing from the South had been prevented from reaching the Pantanal by a high-pressure bubble. Because of this, plenty of hotter and drier air contributed to the shortage of rain through the summer time on the peak of the monsoon season, usually characterised by modifications in atmospheric circulation and precipitation in tropical and subtropical coastal areas as a consequence of uneven heating of land and sea.

The end result was a protracted excessive drought all through the Pantanal, with severely antagonistic results on the biome. “This phenomenon is pure and occurred in an analogous method in São Paulo through the 2014-16 drought,” Marengo stated.

Amplified influence

In response to Marengo, it’s not but doable to foresee whether or not the Pantanal will face extra extreme droughts within the years forward. The issue can solely be prevented if there may be the correct amount of rain on the proper time. “It is no use getting rain now, in March, on the finish of the wet season, after which between December this yr and February 2022, for instance,” he stated. “This compromises the wet season and will increase the chance of extra wildfires within the Pantanal.”

Drought within the Pantanal can’t be blamed solely on international local weather change as a result of it’s a pure occasion and local weather change is a long-term course of. The latest drought differed from these seen within the 1950s and 1960s when the planet was cooler. “What’s occurring now could be that these pure droughts are struggling the results of local weather instability, and the results are worse as a result of again then there was loads much less human occupancy within the area. Its inhabitants is now extra susceptible to the influence of drought,” Marengo stated.

Extra data:
Jose A. Marengo et al, Excessive Drought within the Brazilian Pantanal in 2019–2020: Characterization, Causes, and Impacts, Frontiers in Water (2021). DOI: 10.3389/frwa.2021.639204