Decadal-scale Variability Research Articles

Quantifying uncertainty in twenty-first century climate change over India

Uncertainties in future changes of temperature and precipitation over the homogenous monsoon regions of India are investigated using the CMIP5 and CESM-LE datasets. The uncertainty is partitioned into epistemic (model) and aleatoric (internal variability) components for each season using the RCP8.5 scenario. The uncertainty in temperature change is dominated by epistemic uncertainty that increases over time. The uncertainty in precipitation change shows a more complex picture. Aleatoric uncertainty can remain quite large and comparable to epistemic uncertainty till the latter part of the twenty-first Century especially during the JJA and SON seasons. Much of the rainfall uncertainty is in the more arid Northwest region with the West Central region (part of the core monsoon area) exhibiting lower uncertainties. Considerable increase in rainfall is seen during the SON season indicating an extended monsoon season. During the DJF season aleatoric uncertainty is much larger than epistemic uncertainty over much of the century and shows considerable decadal scale variability. Using the 40-member CESM-LE ensemble to analyze the influence of ensemble size on aleatoric uncertainty we find that low ensemble sizes can lead to an underestimate of the uncertainty.

Early-warning signals for Dansgaard-Oeschger events in a high-resolution ice core record

The Dansgaard–Oeschger (DO) events, as observed in oxygen isotope ratios from the North Greenland Ice Core Project (NGRIP) record, are an outstanding example of past abrupt climate transitions. Their physical cause remains debated, and previous research indicated that they are not preceded by classical early-warning signals (EWS). Subsequent research hypothesized that the DO events are caused by bifurcations of physical mechanisms operating at decadal timescales, and proposed to search for EWS in the high-frequency fluctuation levels. Here, a time series with 5-year resolution is obtained from the raw NGRIP record, and significant numbers of EWS in terms of variance and autocorrelation increases are revealed in the decadal-scale variability. Wavelet analysis indicates that the EWS are most pronounced in the 10–50-year periodicity band, confirming the above hypothesis. The DO events are hence neither directly noise-induced nor purely externally forced, which provides valuable constraints regarding potential physical causes.

Global lake response to the recent warming hiatus

Understanding temporal variability in lake warming rates over decadal scales is important for understanding observed change in aquatic systems. We analyzed a global dataset of lake surface water temperature observations (1985−2009) to examine how lake temperatures responded to a recent global air temperature warming hiatus (1998−2012). Prior to the hiatus (1985−1998), surface water temperatures significantly increased at an average rate of 0.532 °C decade−1 (±0.214). In contrast, water temperatures did not change significantly during the hiatus (average rate −0.087 °C decade−1 ±0.223). Overall, 83% of lakes in our dataset (129 of 155) had faster warming rates during the pre-hiatus period than during the hiatus period. These results demonstrate that lakes have exhibited decadal-scale variability in warming rates coherent with global air temperatures and represent an independent line of evidence for the recent warming hiatus. Our analyses provide evidence that lakes are sentinels of broader climatological processes and indicate that warming rates based on datasets where a large proportion of observations were collected during the hiatus period may underestimate longer-term trends.

Anomalously weak Labrador Sea convection and Atlantic overturning during the past 150 years.

The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth's climate, redistributing heat and influencing the carbon cycle1, 2. The AMOC has been shown to be weakening in recent years 1 ; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC1, 3-5. Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately AD1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA-sourced from melting glaciers and thickened sea ice that developed earlier in the LIA-weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet 6 . Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here.

Modulation of extreme temperatures in Europe under extreme values of the North Atlantic Oscillation Index.

This paper reports on the influence that extreme values in the tails of the North Atlantic Oscillation (NAO) Index probability density function (PDF) can exert on temperatures in Europe. When the NAO Index enters into its lowest (10% quantile or less) and highest (90% quantile or higher) modes, European temperatures often exhibit large negative or positive departures from their mean values, respectively. Analyses of the joint quantiles of the Index and temperatures (i.e., the simultaneous exceedance of particular quantile thresholds by the two variables) show that temperatures enter into the upper or lower tails of their PDF when the NAO Index also enters into its extreme tails, more often that could be expected from random statistics. Studies of this nature help further our understanding of the manner by which mechanisms of decadal-scale climate variability can influence extremes of temperature-and thus perhaps improve the forecasting of extreme temperatures in weather and climate models.

Response of lower trophic level ecosystems to decadal scale variation of climate system in the North Pacific Ocean

Response of lower trophic level ecosystems to decadal scale variation of climate system in the North Pacific Ocean

Mechanisms of variability in decadal sea-level trends in the Baltic Sea over the 20th century

Abstract. Coastal sea-level trends in the Baltic Sea display decadal-scale variations around a long-term centennial trend. In this study, we analyse the spatial and temporal characteristics of the decadal trend variations and investigate the links between coastal sea-level trends and atmospheric forcing on a decadal timescale. For this analysis, we use monthly means of sea-level and climatic data sets. The sea-level data set is composed of long tide gauge records and gridded sea surface height (SSH) reconstructions. Climatic data sets are composed of sea-level pressure, air temperature, precipitation, evaporation, and climatic variability indices. The analysis indicates that atmospheric forcing is a driving factor of decadal sea-level trends. However, its effect is geographically heterogeneous. This impact is large in the northern and eastern regions of the Baltic Sea. In the southern Baltic Sea area, the impacts of atmospheric circulation on decadal sea-level trends are smaller. To identify the influence of the large-scale factors other than the effect of atmospheric circulation in the same season on Baltic Sea sea-level trends, we filter out the direct signature of atmospheric circulation for each season separately on the Baltic Sea level through a multivariate linear regression model and analyse the residuals of this regression model. These residuals hint at a common underlying factor that coherently drives the decadal sea-level trends in the whole Baltic Sea. We found that this underlying effect is partly a consequence of decadal precipitation trends in the Baltic Sea basin in the previous season. The investigation of the relation between the AMO index and sea-level trends implies that this detected underlying factor is not connected to oceanic forcing driven from the North Atlantic region.

Oxygen isotope geochemistry of Laurentide ice-sheet meltwater across Termination I

We present a new method that quantifies the oxygen isotope geochemistry of Laurentide ice-sheet (LIS) meltwater across the last deglaciation, and reconstruct decadal-scale variations in the δ18O of LIS meltwater entering the Gulf of Mexico between ∼18 and 11 ka. We employ a technique that combines laser ablation ICP-MS (LA-ICP-MS) and oxygen isotope analyses on individual shells of the planktic foraminifer Orbulina universa to quantify the instantaneous δ18Owater value of Mississippi River outflow, which was dominated by meltwater from the LIS. For each individual O. universa shell, we measure Mg/Ca (a proxy for temperature) and Ba/Ca (a proxy for salinity) with LA-ICP-MS, and then analyze the same O. universa for δ18O using the remaining material from the shell. From these proxies, we obtain δ18Owater and salinity estimates for each individual foraminifer. Regressions through data obtained from discrete core intervals yield δ18Ow vs. salinity relationships with a y-intercept that corresponds to the δ18Owater composition of the freshwater end-member. Our data suggest that from 15.5 through 14.6 ka, estimated δ18Ow values of Mississippi River discharge from discrete core intervals range from −11‰ to −21‰ VSMOW, which is consistent with δ18O values from both regional precipitation and the low-elevation, southern margin of the LIS. During the Bølling and Allerød (14.0 through 13.3 ka), estimated δ18Ow values of Mississippi River discharge from discrete core intervals range from −22‰ to −38‰ VSMOW. These values suggest a dynamic melting history of different parts of the LIS, with potential contributions to Mississippi River outflow from both the low-elevation, southern margin of the LIS and high-elevation, high-latitude domes in the LIS interior that were transported to the ablation zone. Prior to ∼15.5 ka, the δ18Owater value of the Mississippi River was similar to that of regional precipitation or low-latitude LIS meltwater, but the Ba concentration in the Mississippi basin was affected by changes in weathering within the watershed, complicating Ba-salinity relationships in the Gulf of Mexico. After 13 ka, our data suggest Mississippi River outflow did not influence surface salinity above our Gulf of Mexico Orca Basin core site. Rather, we hypothesize that open ocean conditions prevailed as sea level rose and the paleoshoreline at the southern edge of North America retreated northward.

Decadal-scale variation in COD and DIN dynamics during the summer in the inner area of the Ariake Sea, Japan

More than 30 years of chemical oxygen demand (COD) and dissolved inorganic nitrogen (DIN) data for the inner area of the Ariake Sea were analyzed with a box model to show the changes in the average seasonal budget and the decadal-scale variation during the summer. The COD peaked in August and March on average. This summertime peak can be explained by an enhanced riverine load and increased primary production. The peak in March suggested additional organic matter production. There were also two peaks in DIN concentration on average: a summertime peak that could be explained by an enhanced riverine load, and a peak in December that was more complicated to explain. From the 1970s to the early 1990s, the bottom water in this area became increasingly hypoxic due to increased COD during the summer, even though there were minimal increases in terrestrial COD and nutrient loads and there were tidal flats covering a widespread area during this period. The increase in COD was caused by increased net ecosystem production, which was due to enhanced primary production induced by an increased freshwater residence time and decreased bivalve grazing. There was a negative feedback control in which hypoxia progressively increased, leading to declines in bivalve biomass, which in turn decreased the grazing pressure limiting primary production, meaning that primary production increased and the area became even more hypoxic. The net DIN production decreased during the 1980s and the 1990s. This was consistent with the change in net ecosystem production according to the COD.

Wild Apple Growth and Climate Change in Southeast Kazakhstan

Wild populations of Malus sieversii [Ldb.] M. Roem are valued genetic and watershed resources in Inner Eurasia. These populations are located in a region that has experienced rapid and on-going climatic change over the past several decades. We assess relationships between climate variables and wild apple radial growth with dendroclimatological techniques to understand the potential of a changing climate to influence apple radial growth. Ring-width chronologies spanning 48 to 129 years were developed from 12 plots in the Trans-Ili Alatau and Jungar Alatau ranges of Tian Shan Mountains, southeastern Kazakhstan. Cluster analysis of the plot-level chronologies suggests different temporal patterns of growth variability over the last century in the two mountain ranges studied. Changes in the periodicity of annual ring-width variability occurred ca. 1970 at both mountain ranges, with decadal-scale variability supplanted by quasi-biennial variation. Seascorr correlation analysis of primary and secondary weather variables identified negative growth associations with spring precipitation and positive associations with cooler fall-winter temperatures, but the relative importance of these relationships varied spatially and temporally, with a shift in the relative importance of spring precipitation ca. 1970 at Trans-Ili Alatau. Altered apple tree radial growth patterns correspond to altered climatology in the Lake Balkhash Basin driven by unprecedented intensified Arctic Oscillations after the late 1970s.

Decadal-scale variations of sedimentary dinoflagellate cyst records from the Yellow Sea over the last 400 years

In recent decades, the Yellow Sea has experienced severe environmental deterioration due to increasing input of anthropogenic pollutants and consequently accelerated eutrophication. Whilst there have been significant advances in documenting historical records of metal pollution in the Yellow Sea region, changes in phytoplankton community structures affected by eutrophication remain understudied. Here, we present a new record of dinoflagellate cyst-based signals in age-dated sediment cores from the Yellow Sea mud deposits to provide better insight into eutrophication history and identification of associated responses of the regional phytoplankton community. It is worthy of note that there were significant variations in abundances and community structures of dinoflagellate cysts in three historical stages in association with increasing anthropogenic activity over the last 400 years. Pervasive effects of human interference altering the Yellow Sea environments are recognized by: 1) an abrupt increase of organic matter, including the diatom-produced biogenic opal concentrations (∼1850); 2) a distinct shift in phytoplankton composition towards dinoflagellate dominance (∼1940), and 3) recent acceleration of dinoflagellate cyst accumulation (∼1990). Particularly in the central Yellow Sea shelf, the anomalously high deposition of dinoflagellate cysts (especially Alexandrium species) is suggested to be a potentially important source of inoculum cells serving as a seed population for localized and recurrent blooms in coastal areas around the Yellow Sea.

Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean

Analyses of the chlorophyll a concentration (chla) from satellite ocean color products have suggested the decadal-scale variability of chla linked to the climate change. The decadal-scale variability in chla is both spatially and temporally non-uniform. We need to understand the spatiotemporal evolution of chla in decadal or multi-decadal timescales to better evaluate its linkage to climate variability. Here, the spatiotemporal evolution of the chla trend in the North Atlantic Ocean for the period 1997–2016 is analyzed using the multidimensional ensemble empirical mode decomposition method. We find that this variable trend signal of chla shows a dipole pattern between the subpolar gyre and along the Gulf Stream path, and propagation along the opposite direction of the North Atlantic Current. This propagation signal has an overlapping variability of approximately twenty years. Our findings suggest that the spatiotemporal evolution of chla during the two most recent decades is part of the multidecadal variations and possibly regulated by the changes of Atlantic Meridional Overturning Circulation, whereas the mechanisms of such evolution patterns still need to be explored.

Decadal-scale variation in diet forecasts persistently poor breeding under ocean warming in a tropical seabird.

Climate change effects on population dynamics of natural populations are well documented at higher latitudes, where relatively rapid warming illuminates cause-effect relationships, but not in the tropics and especially the marine tropics, where warming has been slow. Here we forecast the indirect effect of ocean warming on a top predator, Nazca boobies in the equatorial Galápagos Islands, where rising water temperature is expected to exceed the upper thermal tolerance of a key prey item in the future, severely reducing its availability within the boobies’ foraging envelope. From 1983 to 1997 boobies ate mostly sardines, a densely aggregated, highly nutritious food. From 1997 until the present, flying fish, a lower quality food, replaced sardines. Breeding success under the poor diet fell dramatically, causing the population growth rate to fall below 1, indicating a shrinking population. Population growth may not recover: rapid future warming is predicted around Galápagos, usually exceeding the upper lethal temperature and maximum spawning temperature of sardines within 100 years, displacing them permanently from the boobies’ island-constrained foraging range. This provides rare evidence of the effect of ocean warming on a tropical marine vertebrate.

Hydro-climatic variability and extremes over the Athabasca River basin: Historical trends and projected future occurrence

Since humans and ecosystems require adequate, reliable water supplies, hydro-climatic variability and extremes pose serious threats to society and the environment. Western Canada, including the Athabasca River Basin (ARB), is prone to considerable hydro-climatic variability including periodic extreme droughts and excessive moisture conditions. The main causes of these extremes are persistent, mid-tropospheric circulation patterns that disrupt expected precipitation and temperature. However, no investigation has specifically focused on the occurrence and causes of both past and future hydro-climatologic variability within the ARB. Assessment of the Standardized Precipitation Evapotranspiration Index (SPEI) reveals substantial inter-annual and decadal-scale variability over the entire ARB and its individual reaches, with no discernible trends during the last ~100 years. Evaluation of the 500-hPa circulation patterns associated with identified hydro-climatic extremes shows that major droughts are related to higher frequencies of distinctive ridging patterns over the ARB and fewer incidences of troughing. Excessive moisture conditions tend to have opposite patterns. Projections from several regional climate models reveal an average change toward more drought-like summer and slightly wetter annual conditions over the ARB, but there is a substantial range for individual models ranging from a considerable increase in drought with a higher degree of inter-annual variability, to relatively little change from current conditions. Simulated changes to key atmospheric circulations are consistent with these SPEI projections and indicate that those patterns associated with hydro-climatic extremes will continue in the future and in some cases, increase in frequency. Results from this analysis have quantified historical hydro-climatic variability in the ARB and have provided insight into potential future conditions as driven by changes to surface climate and synoptic-scale atmospheric circulation patterns.

Twentieth-Century Trends in the Annual Cycle of Temperature across the Northern Hemisphere

AbstractThe annual cycle of surface air temperature is examined across Northern Hemisphere land areas (north of 25°N) by comparing the results from the Climatic Research Unit Time Series (CRU TS) dataset against four reanalysis datasets: two versions of the NOAA Twentieth Century Reanalysis (20CR and 20CRC) and two versions of the ECMWF Twentieth Century Reanalysis, version 2 (ERA-20C) and version 2c (ERA-20CM). The modulated annual cycle is adaptively derived from an ensemble empirical mode decomposition (EEMD) filter, and is used to define the phase and amplitude of the annual cycle. The EEMD method does not impose a simple sinusoidal shape of the annual cycle. None of the reanalysis simulations assimilates surface temperature or land-use data. However, they differ in the parameters that are included: both ERA-20C and 20CR assimilate surface pressure data; ERA-20C also includes surface wind data over the oceans; and ERA-20CM does not assimilate any of these synoptic data. It is demonstrated that synoptic variability is critical for explaining the trends and variability of the annual cycle of surface temperature across the Northern Hemisphere. The CMIP5 forcings alone are insufficient to explain the observed trends and decadal-scale variability, particularly with respect to the decline in the amplitude of the annual cycle throughout the twentieth century. The variability in the annual cycle during the latter half of the twentieth century was unusual in the context of the twentieth century, and was most likely related to large-scale atmospheric variability, although uncertainty in the results is greatest before about 1930.

Variability of the date of monsoon onset over Kerala (India) of the period 1870–2014 and its relation to sea surface temperature

Monsoon onset over Kerala (India) which occurs every year is a major climatic phenomenon that involves large scale changes in wind, rainfall and sea surface temperature (SST). Over the last 150 years, the date of monsoon onset over Kerala (DMOK) has varied widely, the earliest being 11 May, 1918 and the most delayed being 18 June, 1972. DMOK has a long term (1870–2014) mean of 01 June and standard deviation of 7–8 days. We have studied the inter-annual and decadal time scale variability of DMOK and their relation with SST. We found that SST anomalies of large spatial scale similar to those in El Nino/La Nina are associated with the inter-annual variability in DMOK. Indian Ocean between latitudes $$5^{\circ }\hbox {S}$$ and $$20^{\circ }\hbox {N}$$ has two episodes of active convection associated with monsoon onset over Kerala (MOK), one around DMOK and the other about six weeks earlier (called pre-monsoon rain peak or bogus monsoon onset) and in between a two week period of suppressed convection occurs over north Indian Ocean. A prominent decadal time scale variability was found in DMOK having large and statistically significant linear correlation with the SST gradient across the equator over Indian and Pacific oceans, the large correlation persisting for several months prior to the MOK. However, no linear trend was seen in DMOK during the long period from 1870 to 2014.

A comparison of modes of upwelling-favorable wind variability in the Benguela and California current ecosystems

Abstract The California Current System (CCS) has two independent seasonal modes of upwelling variability, summer and winter, driven by different atmospheric processes. The variability of upwelling winds during winter is particularly important as strong, episodic events, driven by atmospheric teleconnections with the equatorial Pacific that are active in this season, impact ecological systems along the west coast of North America. Given the importance of upwelling seasonality to ecosystem function, we hypothesize that the Benguela Current System (BCS) shows similar independent seasonal modes of upwelling variability. To test this hypothesis, compare modes of variability between systems, and investigate potential drivers, we use an upwelling index derived from NCEP2 wind data (1979–2014) for the northern, southern, and Agulhas Bank areas of the BCS. In the northern and southern BCS, only one mode of upwelling variability is observed: year-round in the north and during the austral spring and summer (October through April) in the south. The Agulhas Bank region shows two modes of seasonal variability. Based on this 35-year dataset, summer upwelling modes in both the CCS and BCS appear to have similar decadal-scale variability. The other modes of variability (winter mode in the CCS and the non-seasonal second mode in the BCS) are correlated with year-to-year variability in the positioning of regional oceanic high-pressure systems. The leading mode of upwelling variability in the Agulhas Bank region, in the austral summer/fall, is highly correlated with sea level pressure as well as sea surface temperature in the equatorial Pacific, in a spatial and seasonal pattern (boreal winter) resembling the El Nino-Southern Oscillation. Across the CCS, modes of upwelling variability are similar to one another, while modes differ between regions in the BCS. This difference could lead to regional mismatches in favorable ecological conditions. In contrast with the spatially synchronous winter variability influencing the entire CCS ecosystem, substantial regional variation in the BCS may have strong effects on ecosystem functions, especially for species (e.g., small pelagic fish) that migrate between the Agulhas Bank and other areas of the BCS.

Pacific North American circulation pattern links external forcing and North American hydroclimatic change over the past millennium

Land and sea surface temperatures, precipitation, and storm tracks in North America and the North Pacific are controlled to a large degree by atmospheric variability associated with the Pacific North American (PNA) pattern. The modern instrumental record indicates a trend toward a positive PNA phase in recent decades, which has led to accelerated warming and snowpack decline in northwestern North America. The brevity of the instrumental record, however, limits our understanding of long-term PNA variability and its directional or cyclic patterns. Here we develop a 937-y-long reconstruction of the winter PNA based on a network of annually resolved tree-ring proxy records across North America. The reconstruction is consistent with previous regional records in suggesting that the recent persistent positive PNA pattern is unprecedented over the past millennium, but documents patterns of decadal-scale variability that contrast with previous reconstructions. Our reconstruction shows that PNA has been strongly and consistently correlated with sea surface temperature variation, solar irradiance, and volcanic forcing over the period of record, and played a significant role in translating these forcings into decadal-to-multidecadal hydroclimate variability over North America. Climate model ensembles show limited power to predict multidecadal variation in PNA over the period of our record, raising questions about their potential to project future hydroclimatic change modulated by this circulation pattern.

Why Has the Relationship between Indian and Pacific Ocean Decadal Variability Changed in Recent Decades?

Abstract Both the Indian and Pacific Oceans exhibit prominent decadal time scale variations in sea surface temperature (SST), linked dynamically via atmospheric and oceanic processes. However, the relationship between SST in these two basins underwent a dramatic transformation beginning around 1985. Prior to that, SST variations associated with the Indian Ocean basin mode (IOB) and the interdecadal Pacific oscillation (IPO) were positively correlated, whereas afterward they were much less clearly synchronized. Evidence is presented from both observations and coupled state-of-the-art climate models that enhanced external forcing, particularly from increased anthropogenic greenhouse gases, was the principal cause of this changed relationship. Using coupled climate model experiments, it is shown that without external forcing, the evolution of the IOB would be strongly forced by variations in the IPO. However, with strong external forcing, the dynamical linkage between the IOB and the IPO weakens so that the negative phase IPO after 2000 is unable to force a negative phase IOB-induced cooling of the Indian Ocean. This changed relationship in the IOB and IPO led to unique SST patterns in the Indo-Pacific region after 2000, which favored exceptionally strong easterly trade winds over the tropical Pacific Ocean and a pronounced global warming hiatus in the first decade of the twenty-first century.

Spatiotemporal variability modes of surface air temperature in South America during the 1951–2010 period: ENSO and non‐ENSO components

ABSTRACTThe dominant seasonal surface air temperature (SAT) anomalous modes over entire South America (SA) for the 1951–2010 period were investigated. The El Niño‐Southern Oscillation (ENSO) and non‐ENSO (residual – RES) characteristics of the SAT anomalous modes and the associated precipitation and temperature advection anomalies were discussed. The SAT (referred to as TOT) and RES modes were obtained from the empirical orthogonal function analyses, and the ENSO modes from the correlation analyses between the SAT anomalies and the Oceanic Niño index. The SAT TOT modes are in general, weakly linked to the ENSO, except for the first summer and the fourth spring TOT modes. For these two modes, the precipitation variations are more crucial than the temperature advection variations in defining the SAT anomaly patterns. On the other hand, the first winter and autumn TOT modes contain mostly the non‐ENSO components and feature an extensive warmed area in tropical and subtropical SA. For these modes, the subtropical warming is due to the temperature advection. The TOT modes with a weak relation to the ENSO and the corresponding RES modes show a dipolar pattern with a warm node in tropical SA and the cold one in extratropical SA, and is determined mostly by the precipitation. Nevertheless, the cold advection reinforces the cold node of the winter and summer modes. In some cases, the regional systems contribute to the SAT anomalies. The South American low‐level jet contributes to the positive SAT anomalies in central and eastern Brazil for the second winter and first spring RES modes and the South Atlantic Convergence Zone influences the first summer RES mode. The SAT modes describe mostly the interannual variations of the SAT patterns over SA, but some of them also contain decadal and multidecadal time scale variations.