Atmospheric Circulation Variability Research Articles

How to Recognize a True Mode of Atmospheric Circulation Variability

AbstractIt has been demonstrated several times that when principal component analysis (PCA) is used for detection of modes of atmospheric circulation variability (teleconnections), principal components must be rotated. Despite it, unrotated PCA is still often used. Here we demonstrate on the examples of North Atlantic Oscillation (NAO), Arctic Oscillation (AO), Barents Oscillation (BO), and the summer East Atlantic (SEA) pattern that unrotated PCA results in patterns that are artifacts of the analysis method rather than true modes of variability. This claim is based on the comparison of the spatial patterns of the modes with spatial autocorrelations, on the sensitivity of the patterns to spatial and temporal subsampling, and, for the SEA pattern, on correlations with tropical sea surface temperature. Unlike NAO, which is defined by rotated PCA, the other modes, that is, AO, BO, and SEA pattern, defined by unrotated PCA, do not correspond well to underlying autocorrelation structures and are more sensitive to choices of spatial domain and time interval over which they are defined. We reiterate that a great care must be taken when interpreting outputs of PCA when applied to the detection of modes of circulation variability: a comparison with spatial autocorrelations and check for their spatial and temporal stability are necessary to distinguish true modes from statistical artifacts, which we call “ghost patterns.”

The Driving Processes of Concurrent Hot and Dry Extreme Events in China

AbstractSubseasonal heatwave-driven concurrent hot and dry extreme events (HDEs) can cause substantial damage to crops, and hence to lives and livelihoods. However, the physical processes that lead to these devastating events are not well understood. Based on observations and reanalysis data for 1979–2016 over China, we show that HDEs occur preferentially over central and eastern China (CEC) and southern China (SC), with a maximum of three events per year along the Yangtze Valley. The probability of longer-lived and potentially more damaging HDEs is larger in SC than in CEC. Over SC the key factors of HDEs—positive anomalies of surface air temperature and evapotranspiration, and negative anomalies of soil moisture—begin two pentads before maximizing at the peak of the HDEs. These anomalies occur south of a positive height anomaly at 200 hPa, associated with a large-scale subsidence anomaly. The processes over CEC are similar to those for SC, but the anomalies begin one pentad before the peak. HDE frequency is strongly related to the Silk Road pattern and the boreal summer intraseasonal oscillation. Positive phases of the Silk Road pattern and suppressed phases of the boreal summer intraseasonal oscillation are associated with positive height anomalies over CEC and SC, increasing HDE frequency by about 35%–54% relative to the climatological mean. Understanding the effects of subseasonal and seasonal atmospheric circulation variability, such as the Silk Road pattern and boreal summer intraseasonal oscillation, on HDEs is important to improve HDE predictions over China.

Yearly evolution of Euro-Atlantic weather regimes and of their sub-seasonal predictability

It is often assumed that weather regimes adequately characterize atmospheric circulation variability. However, regime classifications spanning many months and with a low number of regimes may not satisfy this assumption. The first aim of this study is to test such hypothesis for the Euro-Atlantic region. The second one is to extend the assessment of sub-seasonal forecast skill in predicting the frequencies of occurrence of the regimes beyond the winter season. Two regime classifications of four regimes each were obtained from sea level pressure anomalies clustered from October to March and from April to September respectively. Their spatial patterns were compared with those representing the annual cycle. Results highlight that the two regime classifications are able to reproduce most part of the patterns of the annual cycle, except during the transition weeks between the two periods, when patterns of the annual cycle resembling Atlantic Low regime are not also observed in any of the two classifications. Forecast skill of Atlantic Low was found to be similar to that of NAO+, the regime replacing Atlantic Low in the two classifications. Thus, although clustering yearly circulation data in two periods of 6 months each introduces a few deviations from the annual cycle of the regime patterns, it does not negatively affect sub-seasonal forecast skill. Beyond the winter season and the first ten forecast days, sub-seasonal forecasts of ECMWF are still able to achieve weekly frequency correlations of r = 0.5 for some regimes and start dates, including summer ones. ECMWF forecasts beat climatological forecasts in case of long-lasting regime events, and when measured by the fair continuous ranked probability skill score, but not when measured by the Brier skill score. Thus, more efforts have to be done yet in order to achieve minimum skill necessary to develop forecast products based on weather regimes outside winter season.

Eurasian cooling in response to Arctic sea-ice loss is not proved by maximum covariance analysis

The extent to which the ongoing decline in Arctic sea ice affects mid-latitude climate has received great attention and polarised opinions. The basic issue is whether the inter-annual variability in Arctic sea ice is the cause of, or the response to, variability in mid-latitude atmospheric circulation. Mori et al. (M19) claims to have reconciled previous conflicting studies by showing that a consistent mid-latitude climate response to inter-annual sea-ice anomalies can be identified between the ERA-Interim reanalysis, taken as observations, and an ensemble of atmosphere-only (AMIP) climate model simulations. Here we demonstrate that such a conclusion cannot be drawn, due to issues with the interpretation of the maximum covariance analysis performed. After applying the M19 approach to the output from a simple statistical model, we conclude that a predominant atmospheric forcing of the sea-ice variability, rather than the converse, is a more plausible explanation of the results presented in M19.

Summertime atmosphere–sea ice coupling in the Arctic simulated by CMIP5/6 models: Importance of large-scale circulation

Summertime barotropic high pressure in the Arctic and its induced warmer and wetter atmosphere over sea ice are suggested to be important contributors to September sea ice loss on interannual and interdecadal time scales in the past decades. Using ERA5 and other reanalysis data, we find that atmospheric warming and moistening in the Arctic, synchronized by high latitude atmospheric circulation variability, work in tandem to melt sea ice through increasing downwelling longwave radiation at the surface. To what extent this atmosphere-longwave radiation-sea ice relationship can be captured in CMIP5 and 6 remains unknown and thus addressing this question is the objective of this study. To achieve this goal, we construct a process-oriented metric emphasizing the statistical relationship between atmospheric temperature and humidity with sea ice, which can effectively rank and differentiate the performance of 30 CMIP5 climate models in reproducing the observed connection. Based on our evaluation, we suggest that most available models in CMIP5 and 6 have a limitation in reproducing the full strength of the observed atmosphere–sea ice connection. This limitation likely stems from a weak impact of downwelling longwave radiation in linking sea ice with circulation associated with the weak sensitivity of the temperature and humidity fields to circulation variability in the Arctic. Thus, further efforts should be devoted to understanding the sources of these models’ limitations and improve skill in simulating the effects of atmospheric circulation in coupling temperature, humidity, surface radiation and sea ice together during Arctic summer.

Synoptic processes over the Kodar glacier zone during the ablation period

The small glaciers of the Kodar ridge (south of Eastern Siberia), located inland Asia under the influence of both Atlantic and Pacific air transport, are the valuable objects for studying their response to changes in mid-latitude atmospheric circulation. However, detailed meteorological studies on the glaciers have been limited so far. For the first time, in July–August 2019, the meteorological characteristics were measured on the Sygyktinsky glacier using automatic weather station. We have analyzed the relationship between variations of large-scale atmospheric circulation and meteorological regime of the glacier using the NCEP–NCAR reanalysis data. During the observation period, Kodar was under the influence of a positive geopotential anomaly in the lower troposphere, which determined increased temperatures and decreased relative humidity and precipitation. Quasi-cyclic fluctuations in meteorological time series (e.g. air temperature) reflect the influence of large scale synoptic changes caused by the front passages, warm and cold air advections. High ablation rates on the glacier were associated with anticyclones, subtropical ridges, and warm air advections (from southeast and southwest), while decreased ablation was observed during the cyclone passage and cold air advection (from north, northeast, and west).

Modes of Atmospheric Circulation Variability in the Northern Extratropics: A Comparison of Five Reanalyses

AbstractModes of low-frequency circulation variability in the Northern Hemisphere extratropics are compared between five reanalyses. Circulation modes are detected by rotated principal component analysis (PCA) of monthly mean 500-hPa geopotential heights between 1957 and 2002, separately for individual seasons. The quantification of differences between reanalyses is based on the percentage of grid points (approximately corresponding to the percentage of area) where the spatial representations of a mode (loadings) significantly differ between reanalyses. The differences between surface-input reanalyses (20CRv2c, ERA-20C) and full-input reanalyses (NCEP-1, ERA-40, JRA-55) are larger than differences within the reanalysis groups in all seasons except for autumn. The causes of the differences are of two kinds. First, the differences may be inherent to PCA: namely, the spatial structure of the modes may be sensitive to the number of components rotated. This concerns only a few modes. Second, the differences may reflect real correlation structures in reanalysis data. We demonstrate that the differences concentrate in three or fewer modes in each season. The reanalysis most different from the rest is 20CRv2c, with the differences concentrating over the southern half of Asia and in the subtropical belt over the Pacific and adjacent southwestern North America. The 20CRv2c reanalysis disagrees from other reanalyses there predominantly before the 1980s, which points to the impact of insufficient amount of assimilated observations. On the contrary, ERA-20C exhibits a higher agreement with full-input reanalyses, which is why we recommend it for studies of atmospheric circulation over the entire twentieth century.

Inter-hemispheric synchroneity of Holocene precipitation anomalies controlled by Earth\u2019s latitudinal insolation gradients

Atmospheric circulation is a fundamental component of Earth’s climate system, transporting energy poleward to partially offset the latitudinal imbalance in insolation. Changes in the latitudinal distribution of insolation thus force variations in atmospheric circulation, in turn altering regional hydroclimates. Here we demonstrate that regional hydroclimates controlled by the Northern Hemisphere mid-latitude storm tracks and the African and South American Monsoons changed synchronously during the last 10 kyrs. We argue that these regional hydroclimate variations are connected and reflect the adjustment of the atmospheric poleward energy transport to the evolving differential heating of the Northern and Southern Hemispheres. These results indicate that changes in latitudinal insolation gradients and associated variations in latitudinal temperature gradients exert important control on atmospheric circulation and regional hydroclimates. Since the current episode of global warming strongly affects latitudinal temperature gradients through Arctic amplification, our results can inform projections of likely inter-hemispheric precipitation changes in the future.

An attempt to explain recent changes in European snowfall extremes

Abstract. The goal of this work is to investigate and explain recent changes in total and maximum yearly snowfall from daily data in light of current global warming or the interdecadal variability of atmospheric circulation. We focus on the period 1979–2018 and compare two different datasets: the ERA5 reanalysis data and the E-OBSv20.0 data, where snowfall is identified from rainfall by applying a threshold to temperature. We compute changes as differences from quantities computed for the periods 1999–2018 and 1979–1998. On the one hand, we show that the decline in average snowfall observed in almost all European regions is coherent with previous findings and can be linked to global warming. On the other hand, we observe contrasting changes in maxima and sometimes disagreement in the sign of changes in the two datasets. Coherent positive trends are found for a few countries in the Balkans. These have been investigated in details by looking at modifications in the atmospheric weather patterns as well as local thermodynamic factors concurring to large snowfall events. We link these changes to the stronger prevalence of Atlantic Ridge or blocking patterns associated with deeper cyclonic structures over the Adriatic and Tyrrhenian seas. These cyclones find warmer surfaces and large availability of humidity and convective available potential energy (CAPE), thus producing large snowfall amounts, enhanced by the Stau effect on the Balkan topography.

Australian Rainfall Anomalies in 2018–2019 Linked to Indo‐Pacific Driver Indices Using ERA5 Reanalyses

AbstractThe 2019 and 2018–2019 periods had record low All‐Australia rainfall in both observations and the ECMWF's Reanalysis 5, or ERA5, data set over 1979–2019. An analysis of the relationships between interannual variability of rainfall and atmospheric circulation, vertically integrated moisture flux, and temperature anomalies using ERA5 alone is undertaken. Both standard driver indices and those that combine the Pacific and Indian Ocean influences are used. Regression fields for low annual Australian rainfall show a widespread negative rainfall anomaly extending into the east Indian Ocean or IND region and a positive anomaly in the western Pacific PAC region. A moisture flux anomaly takes moisture eastwards toward PAC. This pattern largely persists in the four seasons. In March–May 2019 it can be partially linked to a positive Niño 3.4 anomaly and in June–August to a positive Indian Ocean Dipole. For the annual case, the detrended Niño 4 index explains 24% of the 2019 ERA5 Australian rainfall deficit. This rises to 38% for the 2018–2019 deficit (46% for observations), for the Pacific‐Indian Dipole index that combines the PAC and IND regions, whose sea surface temperature anomalies have opposite effects. The correlation of the index with 2‐year rainfall is −0.7. There is much variability, in the Australian monsoon rainfall especially, that is not linked to simple indices, although rainfall is well matched with moisture flux convergence. This extends to the equatorial zone where the climate of the Maritime Continent can be better examined with ERA5's 0.25° data.

North Atlantic centers of action and seasonal to subseasonal temperature variability in Europe and eastern North America

AbstractThe North Atlantic Oscillation (NAO) is one of the most prominent patterns of atmospheric circulation variability in the Northern Hemisphere. Its climate impacts have been identified for regions extending from North America to northern Asia and the Middle East, with implications for sub‐seasonal variability and, in some cases, meteorological trends over multiple years to decades. The NAO itself, however, is the combined expression of two pressure centers: the Icelandic Low and the Azores High. Previous work has shown that when these “centers of action” (CoA) are separated out and studied they can often provide better insight and explanatory power than the NAO does on its own. Here, we analyse the influence that the CoA have on daily minimum air temperature in winter and daily maximum temperature in summer in eastern North America and Europe. The paper has two goals: (a) to characterize CoA associations with temperature on a range of timescales, including sub‐seasonal analyses that reflect short‐term dynamics of the CoA and that are frequently ignored in NAO teleconnection studies, and (b) to evaluate NAO and CoA influence on temperature across seasons (winter and summer) and in upstream and downstream regions (eastern North America and Europe) using a consistent combination of datasets and methods, in order to contextualize results from prior studies that targeted a single region or season. We find that associations with summertime daily maximum and wintertime daily minimum temperatures are strongest for seasonal averages, but select CoA indices inform explanation of temperature variability at subseasonal timescales. The strength of the Icelandic Low and the location of both CoA show strong associations in winter, while in summer the locations of the CoA show temperature associations that are distinct from and sometimes stronger than those found for CoA strength or NAO indices.

Samoorganizuyushchiyesya karty atmosfernoy tsirkulyatsii i mezhgodovaya izmenchivost' gidrometeorologicheskikh poley v Arktike

The article suggests the use of a nonlinear method of data analysis based on a neural network – an algorithm of Kohonen self-organizing maps for the task of typing the atmospheric surface circulation in the Arctic. Based on the construction of self-organizing surface pressure maps, the seasonal and interannual variability of atmospheric circulation in the Arctic for the period 1979–2018 is studied. Several modes were distinguished: cyclonic, two anticyclonic, and three mixed types. Indices of seasonal and annual repeatability of self-organizing atmospheric pressure maps are introduced, which allow us to study the temporal variability of atmospheric circulation modes and a composite method is proposed for calculating connected maps of other hydrometeorological parameters. The regimes of variability of the area of sea ice distribution and sea surface temperature depending on the type of atmospheric circulation are highlighted. Depending on the type of wind regime, there is a change in the area of sea ice distribution due to the variability of the flows of warm Atlantic waters into the Arctic Ocean. The characteristic types of sea surface temperature variability in the Barents Sea are identified, which are modulated by cyclonic / anticyclonic regimes of atmospheric circulation in the region and are an indicator of heat advection by the Atlantic waters. The interrelation is established of the repeatability index of self-organizing atmospheric pressure maps characterizing the types of atmospheric circulation with the variability of the Arctic Oscillation Index. The revealed regularities of the change in the types of cyclonic-anticyclonic atmospheric circulation are manifested in the interannual variability of the introduced repeatability index of selforganizing atmospheric pressure maps, which is a development of the Arctic Oscillation Index, improves understanding of the atmospheric climate circulation regimes in the Arctic.

Late 1980s abrupt cold season temperature change in Europe consistent with circulation variability and long-term warming

Cold season temperatures in Europe have increased rapidly by about 1.2°C in the late 1980s, followed by relatively modest and regionally flat temperature trends thereafter. The abrupt change affected the entire European continent and coincided regionally with abrupt hydroclimatic changes such as a widespread reduction in snow days in Switzerland. However, the drivers and causes of the event are not well understood. Using a dynamical adjustment method based on statistical learning, we find that the continental-scale late 1980s abrupt winter warming and regional decreases in snow days can be attributed to cold conditions in the mid-1980s followed by a few exceptionally warm seasons. Both are caused by random atmospheric circulation variability superimposed upon a long-term and relatively homogenous warming trend, and do not require an external cause or change of the underlying dynamics of the system. This explanation is consistent with simulations from a 21-member regional climate model ensemble, in which four members display comparable abrupt temperature increases regionally driven by circulation and a long-term externally forced response. Overall, our analysis provides an observation-based interpretation of abrupt temperature change at the continental scale, associated hydroclimatic changes regionally, and its drivers. Furthermore, our method might contribute to improved mechanistic understanding of different observed climate phenomena in many regions of the world that experience high variability.

Using ratios in cave guano to assess past environmental changes

AbstractStable isotope ratios of cave bat guano reflect environmental influences at the soil and plant level within the foraging range of the bats. Carbon, nitrogen and hydrogen isotopes have utility in reconstructing precipitation and temperature as well as in tracing the influence of large-scale atmospheric circulation and climate variability. Guano-derived stable isotope time series have been demonstrated to effectively provide high-resolution records of palaeoenvironmental variation from the late Pleistocene to present. Owing to their influence on these isotopes, factors such as bat ecology, species foraging range and site location must be considered when interpreting such records. Research analysing the isotopic composition of guano has provided a highly resolved history of vegetation and climate dynamics previously less understood. In this chapter we discuss the factors influencing the δ13C, δ15N and δ2H values in guano and provide an up-to-date review of cave guano as palaeo-climate archive.

Changing Trends in Rainfall Extremes in the Metropolitan Area of São Paulo: Causes and Impacts

This study analyses observed trends in extreme rainfall events in the Metropolitan Area of São Paulo (MASP). Rainfall data sets with more than 60 years of record in MASP are used. In MASP, extreme rainfall events represent hydro meteorological hazards that trigger flash floods and landslides. Changes in rainfall extremes can be partly due to natural climate variability. In addition, it can also be related to global warming and/or urbanization. Total annual precipitation and the number of days with precipitation of 20 mm exhibit the largest significant increase during 1930-2019. This is better noticed during summer. This tendency is also noticed in the number of days with precipitation of 100 mm or more. Therefore, the positive trend in annual precipitation is mainly due to an increase in the frequency of extreme precipitation events. On the other hand, our analysis shows that the number of consecutive dry days increased. Though these results appear to be contradictory, they indicate an important climate change in recent times. Intense precipitation is concentrated in few days, separated by longer dry spells. The focus is on how atmospheric circulation variations are contributing to these changes. During 1960-2019 the South Atlantic Subtropical Anticyclone has intensified and slightly moved southwestward of its normal position. This change influences the transport of humidity and therefore impact precipitation. This can explain the increase in the precipitation extremes in the MASP. However, other atmospheric systems may also be important.

Temperature and precipitation responses to El Niño-Southern Oscillation in a hierarchy of datasets with different levels of observational constraints

El Nino-Southern Oscillation (ENSO) is the dominant mode of climate variability, affecting climate conditions over large areas of the globe. There are, however, substantial differences in how ENSO teleconnections with regional climate variability are represented in different datasets such as gridded observations and climate models. Here we examine the global responses of temperature and precipitation over land to ENSO within a hierarchy of datasets with different levels of observational constraints. Anomaly maps of observed El Nino and La Nina responses are compared to reanalysis, atmospheric models driven by observed sea surface temperature (SST), and coupled atmosphere–ocean general circulation models. There is a gradual decline in anomaly pattern agreement relative to observations moving down the dataset hierarchy to lower observational constraints. We find a positive relationship between the models’ fidelity in representing ENSO temperature and precipitation, though the relationship is stronger for El Nino teleconnections than La Nina. The models also reproduce El Nino response patterns with greater fidelity than La Nina patterns. Additionally, the fidelity of model-simulated responses to El Nino is related to the magnitude of SST variability in the tropical Pacific, but no such relationship could be found for La Nina responses. This comprehensive evaluation highlights the importance of realistically simulating atmospheric circulation and SST variability to better capturing the patterns of regional climate variability in response to ENSO in climate models.

Quasi-Biweekly Oscillation of the Bay of Bengal–East Asia–Pacific Teleconnection in Boreal Summer

AbstractThe study reported in this paper used ERA-Interim reanalysis data to investigate the intraseasonal variability of the Bay of Bengal (BOB)–East Asia–Pacific teleconnection (BEAP) during the summer between 1979 and 2016. Over this period, the intraseasonal oscillation of the BEAP fell mainly within the quasi-biweekly oscillation (QBWO) band. Variations in atmospheric circulation and precipitation, which may contribute to extreme weather events, showed a significant correlation with the phase transition of the BEAP from the BOB to East Asia and the Pacific. The evolution of the BEAP–QBWO is closely associated with the westward propagation of convective anomalies to the southwestern BOB. Dynamical analysis revealed that anomalous vertical motion coupled with anomalous convective activity over the southern BOB plays an important role in leading the phase propagation of the BEAP–QBWO, and that the horizontal advection anomalies can strengthen the BEAP–QBWO. Linear baroclinic model experiments confirmed that variations in convection over the southern BOB play a leading role in the BEAP–QBWO phase changes. Further research suggests that the boreal summer intraseasonal oscillation can trigger the BEAP–QBWO through downstream propagation of convective disturbances to the southern BOB. This study provides insights into the cause and effect of the BEAP–QBWO, which will help to improve understanding of flood and drought patterns in the Asia–Pacific region.

The North Atlantic as a Driver of Summer Atmospheric Circulation

AbstractSkill in seasonal forecasts in the Northern Hemisphere extratropics is mostly limited to winter. Drivers of summer circulation anomalies over the North Atlantic–European (NAE) sector are poorly understood. Here, we investigate the role of North Atlantic sea surface temperatures (SSTs) in driving summer atmospheric circulation changes. The summer North Atlantic Oscillation (SNAO), the leading mode of observed summer atmospheric circulation variability in the NAE sector, is correlated with a distinct SST tripole pattern in the North Atlantic. An atmospheric general circulation model is used to test whether there are robust atmospheric circulation responses over the NAE sector to concurrent SSTs related to the SNAO. The most robust responses project onto the summer east Atlantic (SEA) pattern, the second dominant mode of observed summer atmospheric circulation variability in the NAE sector, and are most evident at the surface in response to tropical SSTs and at altitude in response to extratropical SSTs. The tropical-to-extratropical teleconnection appears to be due to Rossby wave propagation from SST anomalies, and in turn precipitation anomalies, in the Caribbean region. We identify key biases in the model, which may be responsible for the overly dominant SEA pattern variability, compared to the SNAO, and may also explain why the responses resemble the SEA pattern, rather than the SNAO. Efforts to eradicate these biases, perhaps achieved by higher-resolution simulations or with improved model physics, would allow for an improved understanding of the true response to North Atlantic SST patterns.

Quantifying the internal variability in multi-decadal trends of spring surface air temperature over mid-to-high latitudes of Eurasia

This study investigates the influences of internal climate variability (ICV) on Eurasian spring (March–May) surface air temperature (SAT) trends based on a 30-member ensemble of the Community Earth System Model version 1 (CESM1) from 1979 to 2014. The SAT trends over the mid-high latitude Eurasia vary considerably among individual simulations, indicating a large impact of ICV on SAT trends at regional scales. The leading pattern of internally generated SAT trend variability over Eurasia among the 30 SAT trends displays same sign distribution over the mid-high latitudes of Eurasia. This pattern is associated with the Northern Hemisphere annular mode (NAM) that accounts for about 1/3 of total variance of the spring sea level pressure (SLP) trends. The second pattern of internally generated SAT trend variability features a dipole structure, accompanied by prominent circulation changes over the North Atlantic and Europe. Internal dynamics account for approximately 40–70% of the observed warming over the central Eurasia and the Russian Far East. A dynamical adjustment methodology is employed to remove the effects of internal atmospheric circulation variability. Dynamical adjustment greatly reduces the spread of SAT trends within the ensemble and brings both the simulated and observed trends closer to the ensemble mean. Changes in the Barents–Kara Sea ice and Eurasian snow cover contribute to the remaining spread in SAT trends over the north coast of Russia and in the region north of the Caspian Sea, respectively. Both dynamics and thermodynamics contribute to the Barents–Kara Sea ice and Eurasian snow cover trends.

Climate change impacts on the atmospheric circulation, ocean, and fisheries in the southwest South Atlantic Ocean: a review

We present an interdisciplinary review of the observed and projected variations in atmospheric and oceanic circulation within the southwestern South Atlantic focused on basin-scale processes driven by climate change, and their potential impact on the regional fisheries. The observed patterns of atmospheric circulation anomalies are consistent with anthropogenic climate change. There is strong scientific evidence suggesting that the Brazil Current is intensifying and shifting southwards during the past decades in response to changes in near-surface wind patterns, leading to intense ocean warming along the path of the Brazil Current, the South Brazil Bight, and in the Rio de la Plata. These changes are presumably responsible for the poleward shift of commercially important pelagic species in the region and the long-term shift from cold-water to warm-water species in industrial fisheries of Uruguay. Scientific and traditional knowledge shows that climate change is also affecting small-scale fisheries. Long-term records suggest that mass mortalities decimated harvested clam populations along coastal ecosystems of the region, leading to prolonged shellfishery closures. More frequent and intense harmful algal blooms together with unfavorable environmental conditions driven by climate change stressors affect coastal shellfisheries, impact economic revenues, and damage the livelihood of local communities. We identify future modelling needs to reduce uncertainty in the expected effects of climate change on marine fisheries. However, the paucity of fisheries data prevents a more effective assessment of the impact of climate change on fisheries and hampers the ability of governments and communities to adapt to these changes.