Patterns Of Climate Variability Research Articles

A Simple Statistical Postprocessing Scheme for Enhancing the Skill of Seasonal SST Predictions in the Tropics

Abstract Seasonal prediction systems are subject to systematic errors, including those introduced during the initialization procedure, that may degrade the forecast skill. Here we use a novel statistical postprocessing correction scheme that is based on canonical correlation analysis (CCA) to relate errors in ocean temperature arising during initialization with errors in the predicted sea surface temperature fields at 1–12-month lead time. In addition, the scheme uses CCA of simultaneous SST fields from the prediction and corresponding observations to correct pattern errors. Finally, simple scaling is used to mitigate systematic location and phasing errors as a function of lead time and calendar month. Applying this scheme to an ensemble of seven seasonal prediction models suggests that moderate improvement of prediction skill is achievable in the tropical Atlantic and, to a lesser extent, in the tropical Pacific and Indian Ocean. The scheme possesses several adjustable parameters, including the number of CCA modes retained, and the regions of the left and right CCA patterns. These parameters are selected using a simple tuning procedure based on the average of four skill metrics. The results of the present study indicate that errors in ocean temperature fields due to imperfect initialization and SST variability errors can have a sizable negative impact on SST prediction skill. Further development of prediction systems may be able to remedy these impacts to some extent. Significance Statement The prediction of year-to-year climate variability patterns, such as El Niño, offers potential benefits to society by aiding mitigation and adaptation efforts. Current prediction systems, however, may still have substantial room for improvement due to systematic model errors and due to imperfect initialization of the oceanic state at the start of predictions. Here we develop a statistical correction scheme to improve prediction skill after forecasts have been completed. The scheme shows some moderate success in improving the skill for predicting El Niño and similar climate patterns in seven prediction systems. Our results not only indicate a potential for improving prediction skill after the fact but also point to the importance of improving the way prediction systems are initialized.

Decadal (2010–2019) variability in the marine ecosystems of the North Atlantic

Abstract The “Symposium on Decadal Variability of the North Atlantic and its Marine Ecosystems: 2010–2019” took place in Bergen, Norway, from 20 to 22 May 2022. This event, hosted by the Institute of Marine Research, was jointly sponsored by ICES and NAFO and constitutes the fourth in a series of these symposia that started in 1991. The first symposium’s aim was to review the hydrobiological variability in the decade of the 1980s, addressing the physical environment, plankton, invertebrates, and fish. Subsequent symposia maintained the classical structure, whilst a new theme session covering social sciences was added to the programme in the 2022 edition. Studies of climate impacts on marine ecosystems and living marine resources, including trends and regime shifts, emerged from increasingly longer ecosystem time series across the North Atlantic and subarctic regions. This symposium collection presents key findings discussed during the symposium. Whilst some progress has been made in advancing our ability to understand new trends and patterns of climate change and variability across physical, plankton, and fish communities, more work is needed to integrate these physical-ecological processes and scales with social science.

GEOSPATIAL TECHNIQUES FOR MAPPING AND ANALYSIS OF CLIMATIC VARIABLES IN GOMBE STATE, NORTH-EAST NIGERIA.

This study was carried out to apply satellite- based climatic data in geospatial environment to downscale climatic data into smaller political units and to generate and analyse thematic maps of climatic variables in Gombe State. Spatial climatic data on rainfall, minimum and maximum temperature were obtained from DivaGIS climatic data, while water vapour, solar radiation and wind speed were derived from the WorldClim climatic data. Monthly climatic records from 1981-2021 in twenty-four points evenly spread across Gombe State on rainfall, minimum/maximum temperature and relative humidity were obtained from NASA Power Project to generate the trends and seasonal patterns of temperature and rainfall. Daily climatic records of rainfall were also acquired from globalweather climatic data between 1979 and 2013 and processed to derive the values of rainfall indices using Nieuwolt formula. The monthly climatic records were processed using the kriging module of ArcGIS to transform the point climatic data to spatial data. The result revealed that rainfall in Gombe State occurs mainly between May and September with the peak in August, while the trends in rainfall was decreasing at the southern and northern parts of the state but increasing at the central region. Rainfall onset occurs in the 1st or 2nd week of May in the south, but late (1st week of June) in the north. Rainfall cessation at the central and northern parts of the state occurs in the 3rd or 4th weeks of September, while the southern part experiences late cessation between the 1st and 3rd week of October. The LRS ranges from 95-111 and 160-175 days in the northern and southern parts respectively. High relative humidity was recorded between May and October with the peak in August. Spatial patterns of solar radiation and wind speed were also generated and analyzed. Awareness of the use of satellite based climatic data and geospatial techniques for downscaling climatic data were recommended in order to ease the problems of lack or inadequate climatic data for spatial mapping. Causal factors for the spatial patterns of climatic variables in Gombe state was suggested for further studies.

The association between climatic factors and waterborne infectious outbreaks with a focus on vulnerability in Pakistan: integrative review.

Climate change affects the spread of waterborne infectious diseases, yet research on vulnerability to outbreaks remains limited. This integrative review examines how climate variables (temperature and precipitation) relate to human vulnerability factors in Pakistan. By 2060, mean temperatures are projected to rise from 21.68°C (2021) to 30°C, with relatively stable precipitation. The epidemiological investigation in Pakistan identified Diarrhea (119,000 cases/year), Malaria(2.6 million cases/year), and Hepatitis (A and E) as the most prevalent infections. This research highlighted vulnerability factors, including poverty (52% of the population), illiteracy (59% of the population), limited healthcare accessibility (55% of the population), malnutrition (38% of the population), dietary challenges (48% of the population), as well as exposure to water pollution (80% of the population) and air pollution (55% of the population). The findings suggest that the coordinated strategies are vital across health, environmental, meteorological, and social sectors, considering climatic variability patterns and population vulnerability determinants.

Paradoxical behaviour of rainfall and temperature over ecologically sensitive areas along the Western Ghats.

Initial reports signify some specific isolated locations in different latitudes, revealing a paradoxical increase in both heavy and very heavy rainfall events and also an increment in total, i.e., in both rainfall and temperature, over ecologically sensitive areas along the Western Ghats (WG). This paper presents a coherent study of the full-scale of daily rainfall and temperature over 27 well-spaced stations in the study area to determine its extent and investigate whether or not this contradictory behaviour is real. Also, an attempt has been made to assess the differential behaviour of rainfall, temperature, and heavy rainfall events in association with land use and land cover change (LULC). The analysis revealed that rainfall and temperature over the study area are increasing, whereas heavy rainfall events have increased during 1981-2020 with strong peaks after 2000 around 18-19°N (Mumbai metropolitan region), 14-16°N (mining and quarrying regions in Goa), and 9-12°N (a narrow strip of land spanning across the coastal towns of Karnataka and Kerala) latitudes. The majority of the rainfall excess years coincided with El Nino years, indicating that El Nino does not affect rainfall negatively. However, rainfall over the WG is influenced by local relief and cascading topography. The spatial pattern of average annual rainfall shows a decreasing trend from south to north because the elevation and span of rainfall occurrence are higher in the southern part of WG. The findings of the current research will help in building a strategy to address trends and patterns of climatic variables in association with LULC.

Coupling uncertain patterns of climatic variables in estimating evaporation from open water bodies

Coupling uncertain patterns of climatic variables in estimating evaporation from open water bodies

Data-model comparisons of isotopic and hydrological variabilities of the karstic vadose zone above Villars Cave, SW-France based on 20 years' monitoring record

Because of the great heterogeneity of the limestone fissures, conduits, and reservoirs in karst areas, the understanding of the infiltration in caves and karst terrains is complicated. For example, the time delays observed between rainfall and the various flows into caves, such as shaft flow and seepage flow, exhibit significant variability. To better understand the infiltration above a typical shallow cave, Villars Cave, South-west France, we used both a very long monitoring (>20 years) isotopic data set of rainfall and dripping rates at two different cave gallery levels (14 m and 36 m below the surface, respectively) and a conceptual model (KarstFor) that mix water flows and isotopes. In order to determine the most appropriate reservoir and flow settings, we used one time-lapse electrical resistivity tomography (ERT) image made above the cave, which were incorporated into the KarstFor model. The modeled variations in storage water and infiltration flows are in a good agreement with the observed dripping discharge rates, indicating seasonal variability and various time delays between water excess ((Rainfall-Evapotranspiration) > 0) and drip rates in the different cave levels. The fact that the model strikingly simulates the small, but constant, isotopic difference of drip water δ18O (δ18Od) values between the upper and the lower galleries of Villars Cave, not only reinforces reliability in the model itself but also reveals the impact of multiple infiltration routes and karst reservoir dynamics on the δ18Od. On an inter-annual scale, the observed δ18Od values follow the variations of the water excess and of the cave temperature, which, in the period analyzed, show a marked trend, possibly induced by the climate variability patterns above the cave. Overall, these results are not only important to better understand the infiltration in karstic zones, but also to better interpret speleothem isotopic records widely used in paleo-climate studies.

Fingerprinting Low-Frequency Last Millennium Temperature Variability in Forced and Unforced Climate Models

Abstract Constraining unforced and forced climate variability impacts interpretations of past climate variations and predictions of future warming. However, comparing general circulation models (GCMs) and last millennium Holocene hydroclimate proxies reveals significant mismatches between simulated and reconstructed low-frequency variability at multidecadal and longer time scales. This mismatch suggests that existing simulations underestimate either external or internal drivers of climate variability. In addition, large differences arise across GCMs in both the magnitude and spatial pattern of low-frequency climate variability. Dynamical understanding of forced and unforced variability is expected to contribute to improved interpretations of paleoclimate variability. To that end, we develop a framework for fingerprinting spatiotemporal patterns of temperature variability in forced and unforced simulations. This framework relies on two frequency-dependent metrics: 1) degrees of freedom (≡N) and 2) spatial coherence. First, we use N and spatial coherence to characterize variability across a suite of both preindustrial control (unforced) and last-millennium (forced) GCM simulations. Overall, we find that, at low frequencies and when forcings are added, regional independence in the climate system decreases, reflected in fewer N and higher coherence between local and global mean surface temperature. We then present a simple three-box moist-static-energy-balance model for temperature variability, which is able to emulate key frequency-dependent behavior in the GCMs. This suggests that temperature variability in the GCM ensemble can be understood through Earth’s energy budget and downgradient energy transport, and allows us to identify sources of polar-amplified variability. Finally, we discuss insights the three-box model can provide into model-to-model GCM differences. Significance Statement Forced and unforced temperature variability are poorly constrained and understood, particularly that at time scales longer than a decade. Here, we identify key differences in the time scale–dependent behavior of forced and unforced temperature variability using a combination of numerical climate models and principles of downgradient energy transport. This work, and the spatiotemporal characterizations of forced and unforced temperature variability that we generate, will aid in interpretations of proxy-based paleoclimate reconstructions and improve mechanistic understanding of variability.

Atmospheric Modeling Study on Convection-Triggered Teleconnections Driving the Summer North American Dipole

Abstract The summer North American dipole (NAD) is a pattern of climate variability linked to variations in boreal forest seed production and migration of seed-eating birds. This is a modeling investigation of two teleconnections identified as drivers of the NAD in prior observational work: 1) tropically sourced atmospheric Rossby waves associated with anomalies in the phase distribution of the Madden–Julian oscillation (MJO) (i.e., phases 1 and 6 are anomalously prominent), and 2) a pan-Pacific atmospheric Rossby wave linked to East Asian monsoonal (EAM) convection. Sea surface temperature (SST) boundary forcing experiments were conducted with the Community Earth System Model 2 (CESM2) to trigger convection patterns that align with those observed during EAM and nonuniform phase distributions of MJO. For the EAM case, an El Niño–like SST dipole pattern combined with cool southern Japan SST forcing produced a convection and jet stream shift anomaly over East Asia and the northern Pacific with a positive NAD pattern downstream over North America, similar to the observed pattern when precipitation over East Asia (PEA) is relatively high. A companion experiment with only ENSO-like SST forcing also produced the NAD but featured a different structure over the Eurasian continent with a response resembling the summer east Atlantic (SEA) pattern over eastern North America and the eastern Atlantic. Simulation results suggest that the southern Japan SST forcing region has a secondary importance in triggering the NAD, producing only a somewhat NAD-like pattern by itself and only slightly improving the NAD produced by ENSO-like forcing. Simulations using SST forcing to induce seasonal convection anomalies with spatial patterns similar to anomalously frequent occurrence of MJO phase 1 (phase 6) produced circulation response patterns resembling the positive NAD (negative NAD).

Recent Increase in a Recurrent Pan-Atlantic Wave Pattern Driving Concurrent Wintertime Extremes

Abstract Wintertime extremes such as cold spells and heavy precipitation can have severe socioeconomic impacts, disrupting critical infrastructures and affecting human well-being. Here, we relate the occurrence of local and concurrent cold or wet wintertime extremes in North America and Europe to a recurrent, quasi-hemispheric wave-4 Rossby wave pattern. We identify this pattern as a fundamental mode of the Northern Hemisphere (NH) winter circulation, since wave 4 exhibits phase-locking behavior. Thus, the associated atmospheric circulation and surface anomalies reoccur over the same locations when the pattern’s wave amplitude is high. The wave pattern is most pronounced over the pan-Atlantic region, and increases the probability of extreme cold or wet events by up to 300% in certain areas of North America and Europe, as well as favoring their concurrence at different locations. High-amplitude wave-4 events have increased significantly in frequency over the past four decades (1979–2021), although no clear evidence is found relating this to modes or patterns of climate variability. The identified wave pattern may provide pathways for early prediction of local and concurrent cold or wet wintertime extremes in North America and Europe.

Last glacial hydroclimate variability in the Yucatán Peninsula not just driven by ITCZ shifts

We reconstructed hydroclimate variability in the Yucatán Peninsula (YP) based on stalagmite oxygen and carbon isotope records from a well-studied cave system located in the northeastern YP, a region strongly influenced by Caribbean climate dynamics. The new stalagmite isotopic records span the time interval between 43 and 26.6 ka BP, extending a previously published record from the same cave system covering the interval between 26.5 and 23.2 ka BP. Stalagmite stable isotope records show dominant decadal and multidecadal variability, and weaker variability on millennial timescales. These records suggest significant precipitation declines in the broader Caribbean region during Heinrich events 4 and 3 of ice-rafted discharge into the North Atlantic, in agreement with the antiphase pattern of precipitation variability across the equator suggested by previous studies. On millennial timescales, the stalagmite isotope records do not show the distinctive saw-tooth pattern of climate variability observed in Greenland during Dansgaard–Oeschger (DO) events, but a pattern similar to North Atlantic sea surface temperature (SST) variability. We propose that shifts in the mean position of the Intertropical Convergence Zone (ITCZ), per se, are not the dominant driver of last glacial hydroclimate variability in the YP on millennial timescales but instead that North Atlantic SSTs played a dominant role. Our results support a negative climate feedback mechanism whereby large low latitude precipitation deficits resulting from AMOC slowdown would lead to elevated salinity in the Caribbean and ultimately help reactivate AMOC and Caribbean precipitation. However, because of the unique drivers of future climate in the region, predicted twenty-first century YP precipitation reductions are unlikely to be modulated by this negative feedback mechanism.

Long‐term observed changes of air temperature, relative humidity and vapour pressure deficit in Bolivia, 1950–2019

AbstractThis study analyzes the long‐term observed changes of mean (Tmean), maximum (Tmax) and minimum (Tmin) air temperatures, relative humidity (RH) and vapour pressure deficit (VPD) at different elevation ranges across Bolivia from 1950 to 2019. The linear trends in air temperature series present a significant increase, with no substantial seasonal or spatial differences. On an annual basis, RH exhibited a non‐significant decrease (−0.08% decade−1), while VPD showed a significant increase (0.01 hPa decade−1) (p < 0.05). Although prior research has suggested that highland elevations experience faster warming than the global average, we have not identified a distinct correlation between elevation gradients and differential warming rates in Bolivia. Future research could investigate elevation‐dependent climate trends by examining seasonal and monthly patterns of climatic variables in relation to topographical gradients in various highland regions.

Amplified Decadal Variability of Extratropical Surface Temperatures by Stratosphere‐Troposphere Coupling

AbstractThe dominant pattern of Northern Hemisphere extratropical climate variability is the Northern Annular Mode (NAM), which in wintertime represents the coupling of the stratospheric and tropospheric circulations. The internal variability associated with the NAM has been shown to give rise to substantial uncertainty in climate projections of regional surface air temperatures (SATs), but it's unclear how much of this variability arises from stratosphere‐troposphere coupling processes. Here, using three large‐ensemble coupled climate model simulations from 1850 to 2100 with varying fidelity of stratosphere‐troposphere coupling processes, we demonstrate that regional SAT variability across timescales is amplified when the tropospheric NAM is coupled to the stratospheric NAM. Moreover, models that lack adequate simulation of stratosphere‐troposphere coupling processes may not capture the magnitude of uncertainty in near‐term SAT projections associated with this coupling.

Detecting the main driving force of runoff change in the Beiluo River Basin, China.

Understanding the evolution of runoff and identifying the main driving force of hydrological cycle changes are essential for water resource management. In this study, the spatial and temporal patterns of climate variables and hydrological factors were explored by applying geostatistical analysis and trend analysis in the Beiluo River Basin (BRB), China, and conversions of land use/cover change (LUCC) were assessed using chord diagrams. Contributions of climate change and human activities to runoff change were quantified employing multiple methods. The results show that annual precipitation and actual evapotranspiration increased significantly during the impact period (2004-2014) (p < 0.05), at rates of 19.3 mm/a and 11 mm/a, respectively, and there was a minor upward trend in annual runoff, at a rate of 0.38 mm/a, while annual potential evapotranspiration decreased slightly at a rate of - 3.3 mm/a. Climate variables were the primary contributor to runoff decrease from 2004 to 2011, with an average contribution of - 79% according to the three methods. Human activities were estimated to account for - 81% of runoff change from 2012 to 2014, which was inextricably linked to the increasing LUCC. The results of this study can provide a theoretical basis for regional water resource management under the influence of climate change and human activities.

Lagrangian Characterization of Surface Transport From the Equatorial Atlantic to the Caribbean Sea Using Climatological Lagrangian Coherent Structures and Self‐Organizing Maps

AbstractThis study presents an assessment of the transport of suspended material by surface ocean currents, which have a critical role in determining the connectivity and distribution of living and non‐living material. Lagrangian experiments reveal pathways from the Equatorial Atlantic to 10 strategic regions within the Caribbean Sea, determined by considering the space‐time variability of climatological Lagrangian Coherent Structures, which act as recurrent attracting pathways and transport barriers. Due to windage or Stokes drift, wind forcing is a significant factor in determining the spatial locations where particles cluster and the time needed to reach the Caribbean from the Equatorial Atlantic. Pathways shift westward within the Caribbean and take less time to arrive with increasing wind influence. Depending on the wind effect, the particles show higher confluence in different areas of the Caribbean. A case study is presented for the Mexican Caribbean nearshore area, isolated from ocean‐current trajectories. Here, wind weakens the transport barrier responsible for this isolation and causes particle confluence toward that region. Spatial patterns of the Eulerian velocity identified through Self‐Organizing Maps, with time dependence given by their best matching units, can reproduce the characteristic Lagrangian patterns of surface current climate variability. Our study demonstrates the application of tools from dynamical systems and unsupervised neural networks to understand Lagrangian patterns and identify the processes that drive them. These findings improve our understanding of transport mechanisms of suspended material by surface ocean currents in the Western Atlantic and the Caribbean Sea, which is essential for managing and conserving marine ecosystems.

Reconstructing the pattern of late Quaternary climate through sediment-landform assemblages in the Dhauli Ganga valley (upper Ganga catchment), India

The present study focuses on the reconstruction of the pattern of late Quaternary climate variability through sediment-landform assemblages in the monsoon-dominated Dhauli Ganga valley. The South Tibet Detachment System (STDS) is a major litho-tectonic boundary that divides the Dhauli Ganga valley into two broad geomorphic entities. Towards the north of STDS, the valley is wide and “U” shaped, and the rivers have a braid-meandering channel, implying that the valley was carved by glacial sculpturing in the past. Whereas in the south, deep gorges indicate the dominance of fluvial processes. Based on the stratigraphic position and optical chronologies, the lithified moraines were assigned to Marine Isotopic Stage-3 (MIS-3) they were followed by a major deglaciation event represented by moderately lithified outwash gravels. Following this, a second glacier advance of lesser magnitude is dated 21.3 ± 2.2 ka, corresponding to the Last Glacial Maximum (LGM). A gradual recession of the LGM moraines led to the formation of a proglacial lake which probably persisted until around the onset of a pulsating deglaciation stage represented by outwash gravels dated between 13.4 ± 1.6 and 9.4 ± 0.8 ka. This was also the period when the valleys were overwhelmed by a high sediment water ratio, as indicated by temporary impoundments dated between 15.0 ± 1 ka and 10.0 ± 1 ka. Alluvial fan and debris flow sedimentation overwhelm the valley after around 9 ka and continues till the present.Climatically, the older lithified moraines indicate that glaciers advanced during the cooler MIS-4 or MIS-3. The first major deglaciation event seems to represent the pluvial phase of MIS-3. The presence of LGM moraines indicate that the valley responded to the global cooling and associated enhanced westerlies. In contrast, the chronology of outwash gravels suggests that the valley witnessed insolation driven by the early Holocene strengthened Indian Summer Monsoon (ISM). The undated youngest alluvial fans/debris flows are assigned the mid to late Holocene age (<9.5 ka) and seem to have deposited during the declining phase of ISM (low solar insolation). The study suggests that the landform evolution responded to both the global and regional climate variability indicating the sensitivity of the paraglacial valleys in the monsoon-dominated region to the late Quaternary climate variability.

Climate-induced long-term variations of the Arctic ecosystems

The Arctic is significantly affected by global climate change where the warming trend is twice as fast as the world, and climate variability pattern such as Arctic Oscillation is active with great ecological effects. Most of the previous pioneering studies focused on a single local ecosystem in the Arctic, however, the similarities and differences in the dynamics of the Arctic ecosystems have been poorly understood in a changing climate. In this study, long-term variations and regime shifts of eight large marine ecosystems (LMEs) around the Arctic were explored with focuses on comparison among ecosystems in the Atlantic and Pacific sector of the Arctic ocean, and on the impacts of climate change and variability. Results of Bayesian Dynamic Factor Analysis indicate that the long-term variations of fish abundance in the most of LMEs in Atlantic sector showed an increasing trend before the 1970s/1980s and decreased subsequently, which representing variations of warm-affinity species, with regime shifts mainly observed in the 1970s. While the LMEs in Pacific sector showed an increasing trend before the 1990s, which representing the increase of most of the warm-affinity species with regimes shifts concentrating in the 1970s. Most of the LMEs were found to be regulated by Atlantic Multi-decadal Oscillation, only the Greenland Sea and West Bering Sea LMEs were related to the sea ice concentration and Pacific Decadal Oscillation, respectively. This study can promote understandings on climate-induced variability in Arctic ecosystems at a holistic perspective.

Pecora 22: Remote Sensing for Freshwater and Marine Environments

Pecora 22: Remote Sensing for Freshwater and Marine Environments

Palaeoenvironmental changes in the southwestern Mediterranean (ODP site 976, Alboran sea) during the MIS 12/11 transition and the MIS 11 interglacial and implications for hominin populations

The transition from the Marine Isotope Stage (MIS) 12 glacial (ca. 478–424 ka BP) to the MIS 11 interglacial (ca. 424–365 ka BP) is one of the most remarkable climatic shifts of the Middle Pleistocene and is regarded as a phase of major behavioural innovation for hominins. However, many of the available pollen records for this period are of low resolution or fragmented, limiting our understanding of millennial-scale climatic variability. We present a high-temporal resolution pollen record that encompasses the period between MIS 12 and MIS 10 (434–356 ka BP), recovered from the Ocean Drilling Program (ODP) Site 976 in the Alboran Sea. This study aims to provide new insights into the response of vegetation during the transition and to highlight patterns of climatic variability during MIS 11.The ODP Site 976 pollen record shows the shift from glacial to interglacial at 426 ka BP, highlighted by the transition from Pinus, herbaceous and steppic taxa to temperate and Mediterranean taxa. A climatic optimum for temperate and Mediterranean taxa is identified around 426–400 ka BP, equivalent to substage MIS 11c and synchronous with the maxima in SSTs, greenhouse gas concentrations and insolation. A phase with increased Pinus and Cedrus indicates the return to colder and more arid conditions during substage MIS 11b (400–390 ka BP). Substage MIS 11a (390–367 ka BP) is marked by a period of short-term warming followed by gradual cooling, until the return of glacial conditions during MIS 10. Forest contractions have been linked with high- and moderate-intensity climate events also observed in other pollen records and proxies from the Mediterranean and North Atlantic.Our results confirm the intense shift during the MIS 12/11 transition and show that this region is sensitive to millennial-scale climatic variation during MIS 11. The forest contractions observed in our record during events of millennial-scale variability appear to be less intense than in the central and eastern Mediterranean. This suggests that the southwestern Mediterranean may have been less variable during periods of climatic deterioration, thereby representing a possible ecological niche for vegetation. This may have provided a source of subsistence for hominins during harsher conditions, thus contributing to their demographic expansion and technological innovations.

Variations in Monthly Maximum Gust Speed at St Mary's, Isles of Scilly (UK)

AbstractLong‐term variations in maximum gust speeds have been analyzed using wind measurements recorded at St Mary's, Isles of Scilly, UK, and possible drivers of recent changes have been investigated. A rigorous homogenization procedure has been applied to the wind records to remove discontinuities mainly caused by non‐climatic changes. Trends in magnitude of the homogenized annual and monthly maximum gust speeds have been subsequently estimated. A significant (p &lt; 0.10) decreasing trend of −0.102 m s−1/10 years is exhibited by the annual maximum gust speeds over the period 1928–2011, while a non‐significant (p &gt; 0.10) positive trend characterizes the entire period 1928–2020 of wind measurements. A turning point has been detected in the monthly maximum gust speed series in 2012, followed by a trend reversal. Distinctive differences in the gust trend pattern have been observed among the seasons, with increasing trend in summer, and winter gust speeds exhibiting decline in 1969–2011 and strengthening since 2012. Variations in the monthly maximum gust speeds appear closely related to changes in air temperature and latitudinal pressure gradients. Furthermore, the monthly maximum gust speeds show significant correlation with the main oceanic‐atmospheric circulation patterns in the North Atlantic region. A synergistic effect among the phases of the dominant patterns of climate variability appears to explain the observed decline and recovery trends in winter gusts. Summer gust speeds show a positive correlation with the global land‐ocean temperature deviations from the corresponding 1951–1980 base period mean.