Global Sea Surface Temperature Patterns Research Articles

Unravelling spatiotemporal patterns in global sea surface temperatures with dynamic mode decomposition

AbstractExtracting global sea surface temperature (SST) patterns is essential for understanding climate variability in both regional and global perspective. Traditional methods, limited by assumptions of orthogonality, hinder our ability to fully capture the dynamics of global SST, particularly in the complex Pacific basin. This study introduces dynamic mode decomposition (DMD), a powerful method from fluid dynamics, to extract global SST patterns since 1900. Our analysis shows that DMD successfully captures well‐known patterns like global warming and the Atlantic Multidecadal Oscillation (AMO). More importantly, it reveals three Pacific SST modes that are spatially non‐orthogonal but exhibit distinct characteristics. Spectral analysis shows that these Pacific modes have distinct periodicities: Pacific Multi‐decadal Mode (PMDM, ~50 years), Quasi‐decadal Mode (PQDM, 8–16 years) and Interannual Mode (PIAM, 2–8 years). This highlights DMD's strength in not only capturing known patterns but also separating modes with similar spatial features but unique dynamics. Further analysis reveals significant differences in their impacts on global air temperature. During positive phases, all three modes induce tropical warming, with PIAM exerting the strongest influence and PMDM the weakest. In the Northern Hemisphere, both PQDM and PIAM drive mid‐latitude cooling and high‐latitude warming, with a more pronounced effect from PQDM. PMDM, in contrast, triggers widespread cooling across the Northern extratropics. In the Southern Hemisphere, PMDM's influence on temperature exhibits a distinct latitudinal banding pattern. PIAM and PQDM, on the other hand, exhibit a regionalized impact, primarily concentrated in the Amundsen and Ross Seas, with PQDM's influence extending to the Antarctic continent.

Exploring non-linear modes of the subtropical Indian Ocean Dipole using autoencoder neural networks

The subtropical Indian Ocean Dipole (SIOD) significantly influences climate variability, predominantly within parts of the Southern Hemisphere. This study applies an autoencoder—a type of artificial neural network (ANN)—known for its ability to capture intricate non-linear relationships in data through the process of encoding and decoding—to analyze the spatiotemporal characteristics of the SIOD. The encoded SIOD pattern(s) is compared to the conventional definition of the SIOD, calculated as the sea surface temperature (SST) anomaly difference between the western and eastern subtropical Indian Ocean. The analysis reveals two encoded patterns consistent with the conventional SIOD structure, predominantly represented by the SST dipole pattern south of Madagascar and off Australia’s west coast. During different analysis periods, distinct variability in the global SST patterns associated with the SIOD was observed. This variability underscores the SIOD’s dynamic nature and the challenges of accurately defining modes of variability with limited records. One of the ANN patterns has a substantial congruence match of 0.92 with the conventional SIOD pattern, while the other represents an alternate non-linear pattern within the SIOD. This implies the potential existence of additional non-linear SIOD patterns in the subtropical Indian Ocean, complementing the traditional model. When global temperature and precipitation are regressed onto the ANN temporal patterns and the conventional SIOD index, both appear to be associated with anomalous climate conditions over parts of Australia, with several other consistent global impacts. Nevertheless, due to the non-linear nature of the ANN patterns, their effects on local temperature and precipitation vary across different regions as compared to the conventional SIOD index. This study highlights that while the conventional SIOD pattern is consistent with the ANN-derived SIOD pattern, the climate system’s complexity and non-linearity might require ANN modeling to advance our comprehension of climatic modes.

Greater committed warming after accounting for the pattern effect

Our planet’s energy balance is sensitive to spatial inhomogeneities in sea surface temperature and sea ice changes, but this is typically ignored in climate projections. Here, we show the energy budget during recent decades can be closed by combining changes in effective radiative forcing, linear radiative damping and this pattern effect. The pattern effect is of comparable magnitude but opposite sign to Earth’s net energy imbalance in the 2000s, indicating its importance when predicting the future climate on the basis of observations. After the pattern effect is accounted for, the best-estimate value of committed global warming at present-day forcing rises from 1.31 K (0.99–2.33 K, 5th–95th percentile) to over 2 K, and committed warming in 2100 with constant long-lived forcing increases from 1.32 K (0.94–2.03 K) to over 1.5 K, although the magnitude is sensitive to sea surface temperature dataset. Further constraints on the pattern effect are needed to reduce climate projection uncertainty. Earth’s energy budget depends on the global sea surface temperature pattern, which is currently counteracting warming more strongly than expected in the future. Including this pattern effect in projections causes committed warming with present-day forcing to exceed the Paris goals, implying less leeway than anticipated.

Dominant Influence of ENSO-Like and Global Sea Surface Temperature Patterns on Changes in Prevailing Boreal Summer Tropical Cyclone Tracks over the Western North Pacific

AbstractA conventional empirical orthogonal function (EOF) analysis is performed on summertime (May–October) western North Pacific (WNP) tropical cyclone (TC) track density anomalies during 1970–2012. The first leading EOF mode is characterized by a consistent spatial distribution across the WNP basin, which is closely related to an El Niño–Southern Oscillation (ENSO)-like pattern that prevails on both interannual and interdecadal time scales. The second EOF mode is represented by a tripole pattern with consistent changes in westward and recurving tracks but with an opposite change for west-northwestward TC tracks. This second EOF pattern is dominated by consistent global sea surface temperature anomaly (SSTA) patterns on interannual and interdecadal time scales, along with a long-term increasing global temperature trend. Observed WNP TC tracks have three distinct interdecadal epochs (1970–86, 1987–97, and 1998–2012) based on EOF analyses. The interdecadal change is largely determined by the changing impact of ENSO-like and consistent global SSTA patterns. When global SSTAs are cool (warm) during 1970–86 (1998–2012), these SSTAs exert a dominant impact and generate a tripole track pattern that is similar to the positive (negative) second EOF mode. In contrast, a predominately El Niño–like SSTA pattern during 1987–97 contributed to increasing TC occurrences across most of the WNP during this 11-yr period. These findings are consistent with long-term trends in TC tracks, with a tripole track pattern observed as global SSTs increase. This study reveals the potential large-scale physical mechanisms driving the changes of WNP TC tracks in association with climate change.

Oceanic Drivers of Widespread Summer Droughts in the United States Over the Common Era

AbstractWe examine oceanic drivers of widespread droughts over the contiguous United States (herein pan‐CONUS droughts) during the Common Era in what is one of the first analyses of the new Paleo Hydrodynamics Data Assimilation (PHYDA) product. The canonical understanding of oceanic influences on North American hydroclimate suggests that pan‐CONUS droughts are forced by a contemporaneous cold tropical Pacific Ocean and a warm tropical Atlantic Ocean. We test this hypothesis using the paleoclimate record. Composite analyses find a robust association between pan‐CONUS drought events and cold tropical Pacific conditions, but not with warm Atlantic conditions. Similarly, a self‐organizing map analysis shows that pan‐CONUS drought years are most commonly associated with a global sea surface temperature pattern displaying strong La Niña and cold Atlantic Multidecadal Oscillation (AMO) conditions. Our results confirm previous model‐based findings for the instrumental period and show that cold tropical Pacific Ocean conditions are the principal driver of pan‐CONUS droughts on annual timescales.

How do the strength and type of ENSO affect SST predictability in coupled models.

The effects of amplitude and type of the El Niño-Southern Oscillation (ENSO) on sea surface temperature (SST) predictability on a global scale were investigated, by examining historical climate forecasts for the period 1982–2006 from air-sea coupled seasonal prediction systems. Unlike in previous studies, SST predictability was evaluated in different phases of ENSO and for episodes with various strengths. Our results reveal that the seasonal mean Niño 3.4 index is well predicted in a multi-model ensemble (MME), even for four-month lead predictions. However, coupled models have particularly low skill in predicting the global SST pattern during weak ENSO events. During weak El Niño events, which are also El Niño Modoki in this period, a number of models fail to reproduce the associated tri-pole SST pattern over the tropical Pacific. During weak La Niña periods, SST signals in the MME tend to be less persistent than observations. Therefore, a good ENSO forecast does not guarantee a good SST prediction from a global perspective. The strength and type of ENSO need to be considered when inferring global SST and other climate impacts from model-predicted ENSO information.

Influence of sea surface temperature variability on global temperature and precipitation extremes

The HadISST1 data set was used to categorize seasonal patterns of observed global sea surface temperature (SST) variability between 1870 and 2006 using the method of Self‐Organizing Maps (SOM). Eight patterns represented the majority of global SST variations associated with the El Niño–Southern Oscillation (ENSO). Time series of the eight patterns exhibited periods with “preferred” SST states since the late 19th century, i.e., when one or more patterns occurred more frequently than in other periods. The eight patterns were used to investigate the global land‐based response of observed extreme temperature and precipitation indices from the HadEX data set to different nodes of SST variability between 1951 and 2003. Results showed very strong statistically significant opposite temperature and precipitation extremes associated with the first pattern (strong La Niña) and the last pattern (strong El Niño). Extreme maximum temperatures were significantly cooler during strong La Niña events than strong El Niño events over Australia, southern Africa, India, and Canada while the converse was true for United States and northeastern Siberia. These responses were larger when global warming was retained. Even intermediate patterns representing a shift from a weak El Niño to a weak La Niña with associated variability in the North Atlantic were linked with statistically significant increases in warm nights and warm days particularly across Scandinavia and northwest Russia. While the link between precipitation extremes and global SST patterns was less spatially coherent, there were large areas across North America and central Europe, which showed statistically significant differences in the response to opposite phases of the El Niño–Southern Oscillation. These results confirm that the variability of global SST anomaly patterns is important for the modulation of extreme temperature and precipitation globally.

Distinct modes of bidecadal and multidecadal variability in a climate reconstruction of the last centuries from a South Pacific coral

The Rarotonga coral Sr/Ca time series (Linsley et al. in Science 290:1145–1148, 2000) provides a near-monthly resolved proxy record of South Pacific climate variability over the last ~300 years. Here we show that two distinct interdecadal, quasi-periodic time components with periods of ~80 and ~25 years can be identified in this time series by Singular Spectrum Analysis. Their associated spatial patterns in the global sea surface temperature (SST) field show notable differences. Whereas the multidecadal component is associated with a global SST pattern that was recently associated with solar forcing on multidecadal timescales, the bidecadal component is associated with a well known pattern of Pacific decadal to interdecadal SST variability.

Summer Drought Patterns in Canada and the Relationship toGlobal Sea Surface Temperatures

Abstract Canadian summer (June–August) Palmer Drought Severity Index (PDSI) variations and winter (December– February) global sea surface temperature (SST) variations are examined for the 63-yr period of 1940–2002. Extreme wet and dry Canadian summers are related to anomalies in the global SST pattern in the preceding winter season. Large-scale relationships between summer PDSI patterns in Canada and previous winter global SST patterns are then analyzed using singular value decomposition (SVD) analysis. The matrix for the covariance eigenproblem is solved in the EOF space in order to obtain the maximum covariance between the singular values of the SST and the PDSI. The robustness of the relationship is established by the Monte Carlo technique, in which the time expansion of the primary EOF analysis is shuffled 1000 times. Results show that the leading three SVD-coupled modes explain greater than 80% of the squared covariance between the two fields. The interannual El Nino–Southern Oscillation (ENSO), the ...

Global patterns of decadal‐scale variability observed in sea surface temperature and lower‐tropospheric circulation fields

The global patterns associated with decadal‐scale variability (DSV) are examined by a lag correlation technique based on local anomaly indices, using the fields of measured sea surface temperature (SST) and 850 hPa geopotential height for the last 50 years. The three dominant patterns are identified, and the variability is examined; the first spreads over the entire Pacific, which is concurrent with the decadal‐scale modulation of the El Niño/Southern Oscillation (DES variability), the second is confined to the local midlatitude North Pacific (LNP variability), and the third extends over the North Atlantic with the decadal North Atlantic Oscillation (NAO) (DNA variability). The global SST pattern of DES variability exhibits large‐scale equatorial symmetry in the Pacific, which is similar to that of the Pacific Decadal Oscillation but is distinguished by the signals in the subtropical frontal zones. These SST anomalies are accompanied by anomalous subtropical highs that appear prior to the anomalous depression around Australia. The LNP variability, which is related with the Arctic Oscillation, is characterized by the SST anomalies along the North Pacific subarctic frontal zone moving eastward accompanied by the anomalous Aleutian Low. This variability develops (decays) without (with) coherent variability in the tropics. It shows the 6‐year quadrature phase relationship with the DES variability, indicative of an interdecadal variability with a period of 24 years. The DNA variability is featured by the atmospheric NAO and by the SST anomalies in four zonal bands that spread in the North Atlantic from the tropics to high latitudes. This variability is independent of either the DES or LNP variability.

Recent large fluctuations in total ozone

Total ozone changes have been examined for the past 29 years at 32 stations selected from the 70 surface stations in the global ozone network. Recent changes have been dominated by negative anomalies of two general types: reductions in the antarctic since 1980 in spring and deficits since late 1982 primarily in middle latitudes and centred on winter and spring. When significant anomalies from the 1963–1979 monthly means are tabulated world-wide, it is found that positive anomalies were substantially in excess in 1970 only, whereas negative anomalies have dominated in each of the years 1983 to 1986. Springtime correlations between ozone and temperature at the south pole for the period 1963–1979 are used in linear regression models to predict ozone from temperature for the period since 1980. Recent observed ozone values are consistently lower than values predicted by these models. A potential contributor to the antarctic springtime deficits is reduced planetary wave transport of ozone from the middle latitudes into the lower polar stratosphere accompanying a change in the atmospheric general circulation pattern that is also manifested in global sea surface temperature patterns. Northern hemisphere middle latitude deficits are thought to be related to trace substances ejected by the El Chichon volcanic eruption in April 1982, although equatorward of 45°N negative anomalies are accentuated by the quasi-biennial oscillation.

Recent large fluctuations in total ozone

AbstractTotal ozone changes have been examined for the past 29 years at 32 stations selected from the 70 surface stations in the global ozone network. Recent changes have been dominated by negative anomalies of two general types: reductions in the antarctic since 1980 in spring and deficits since late 1982 primarily in middle latitudes and centred on winter and spring. When significant anomalies from the 1963–1979 monthly means are tabulated world‐wide, it is found that positive anomalies were substantially in excess in 1970 only, whereas negative anomalies have dominated in each of the years 1983 to 1986. Springtime correlations between ozone and temperature at the south pole for the period 1963–1979 are used in linear regression models to predict ozone from temperature for the period since 1980. Recent observed ozone values are consistently lower than values predicted by these models. A potential contributor to the antarctic springtime deficits is reduced planetary wave transport of ozone from the middle latitudes into the lower polar stratosphere accompanying a change in the atmospheric general circulation pattern that is also manifested in global sea surface temperature patterns. Northern hemisphere middle latitude deficits are thought to be related to trace substances ejected by the El Chichon volcanic eruption in April 1982, although equatorward of 45°N negative anomalies are accentuated by the quasi‐biennial oscillation.