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Catarina became a Category 1 hurri- and relative humidity at 600 hPa favored al., 2016; OLIVER et al., 2017). MHWs can Atlantic during summer. The lack of clouds
cane on the morning of March 26 (MCTAG- convective activity during the Catarina peri- be caused by atmospheric or oceanic pro- allows more solar radiation to reach both
GART-COWAN et al., 2006). On that day, od and were found to be the main compo- cesses, depending on the event and loca- the continent and the ocean causing the
the storm interacted with environmental nents of positive GPI anomalies. However, tion (HOLBROOK et al., 2019). surface heating of the land and sea which
factors that produced the second highest the three largest GPI peaks only appeared MHWs have a devastating impact on leads to heat waves over the continent and
peak in GPI (Figure 3a). Notably, this peak after the system moved into the region of marine ecosystems (SMALE et al., 2019). the ocean, respectively. The cause of these
was formed during the strong increase in low wind shear stress (between 850 and For example, the event that occurred in blocks has also been identified and is asso-
humidity observed between March 25 and 200 hPa levels). Therefore, confirming the Mediterranean in 2003 caused a mass ciated with the Madden Julian Oscillation,
26 (Figure 3g). Meanwhile, the OHC was that the Catarina transition was initiated mortality of at least 25 invertebrate species especially when it is more active in the In-
close to its climatology (Figure 4a). It was by the atypical pattern of dipole blocking from rocky shores (BLACK et al., 2004; OL- dian Ocean (RODRIGUES & WOOLLINGS,
only on March 27 that the hurricane en- (MCTAGGART-COWAN et al., 2006). ITA et al., 2007; GARRABOU et al., 2009). 2017). Furthermore, Costa and Rodrigues
countered abnormally high OHC, and the The areas of positive OHC anomalies sug- The damage caused by MHWs is not limit- (2021), using outputs from the climate
wind field intensified to a maximum of gest that oceanic conditions may have been ed to demersal organisms or coastal eco- models of the Coupled Model Intercompar-
34.7 m/s (VIANNA et al., 2010). favorable for cyclogenesis. However, there systems. The MHW that occurred in the ison Project Phase 6 (CMIP6), identified an
The results suggest a close correspon- was no significant correspondence between Northwest Atlantic Ocean in 2012 had an increasing trend in the occurrence, intensity,
dence between major positive GPI anoma- such anomalies and the main stages of Cata- impact on fish of great commercial impor- duration, and spatial extent of these MHWs
lies and the main stages of Catarina’s life cy- rina’s development. Unlike the OHC in March tance (MILLS et al., 2013). When tempera- in the Southwest Atlantic, both for the peri-
cle, especially when the system developed 2004, the GPI was the highest between tures are as extreme as the event that per- od 2021-2050 as for the period 2071-2100,
a subtropical cyclone structure, underwent March of all years (1990-2019). Therefore, sisted in the Northwest Pacific Ocean from analyzing a moderate and a more extreme
a tropical transition, and intensified into a the results of Lauton et al. (2021) indicate 2014 to 2016, the MHW can have negative scenario of climate change. Furthermore,
Category 1 hurricane. Lauton et al. (2021) that the GPI is potentially a good index for effects even on birds and other marine ani- the results show that the southwestern
speculate that even the extratropical pre- obtaining a threshold for cyclogenesis in the mals (CAVOLE et al., 2016). Recently, Smith South Atlantic can reach a quasi-permanent
cursor of Catarina received important con- region. This will likely affect future investiga- et al. (2021) provided a global perspective state of MHWs by the end of the 21st cen-
tributions from the interaction with high tions into the impacts of climate change on on the impacts of MHWs on human soci- tury, with MHWs lasting all summer.
GPI values. Vorticity anomalies at 850 hPa the likelihood of other such extreme events. eties. Ecological impacts have ranged from There are still no studies on MHWs in
harmful algal blooms and mass mortality other parts of the South and Tropical At-
3. Marine Heatwaves events to reconfigurations of entire eco- lantic, but Figure 5 shows an increase in
systems, affecting habitat, regulation, and the occurrence of these extreme events in
Climate change substantially affects the Marine Heatwaves (MHW). An MHW is de- ecosystem services globally. The economic practically the entire South and Tropical
planet and society, especially by increas- fined as a prolonged (minimum of 5 days) costs of individual MHW events exceeded Atlantic during the summer, with positive

ing the intensity and frequency of extreme event of sea surface temperatures (SST) US$800 million in direct losses and US$3.1 accumulated intensity values throughout
events, such as floods, droughts and heat above the 90th percentile threshold in rela- billion in indirect losses of ecosystem ser- almost the entire coast of Brazil. Unfortu-
waves, with underdeveloped and devel- tion to a climatology of at least 30 years of vices over several years. nately, the impacts of MHWs on the ma-
oping countries being the most affected data (HOBDAY et al., 2016, 2108). In addi- Although its importance has been rine ecosystems of the South and Tropical
(TRENBERTH et al., 2007). Although most tion to global-scale studies on the duration, proven, there are few studies on MHWs Atlantic and their economic consequences
studies focus on extremes over the conti- frequency and intensity of MHWs, surveys and their properties for the South Atlan- have not been studied in depth. Brauko et
nents, Oliver et al. (2018) found that there were conducted for specific events that oc- tic. Rodrigues et al. (2019) showed that al. (2020) identified a decrease in species
has been a significant increase in the fre- curred in the North Pacific, North Atlantic, atmospheric blockages over southeastern diversity in planktonic and benthic com-
quency, duration and intensity of extreme Western Australia and the Mediterranean Brazil are responsible for up to 60% of munities in the coastal region of Santa
temperature events in the oceans, called Sea (SCANNELL et al., 2016; HOBDAY et MHW events in the southwestern South Catarina as a result of MHWs combined

410 BLUE ECONOMY Ocean and Climate: New Challenges 411