Fast Warming Research Articles

Fast local warming is the main driver of recent deoxygenation in the northern Arabian Sea

Abstract. The Arabian Sea (AS) hosts one of the most intense oxygen minimum zones (OMZs) in the world. Observations suggest a decline in O2 in the northern AS over the recent decades accompanied by an intensification of the suboxic conditions there. Over the same period, the local sea surface temperature has risen significantly, particularly over the Arabian Gulf (also known as Persian Gulf, hereafter the Gulf), while summer monsoon winds may have intensified. Here, we simulate the evolution of dissolved oxygen in the AS from 1982 through 2010 and explore its controlling factors, with a focus on changing atmospheric conditions. To this end, we use a set of eddy-resolving hindcast simulations forced with winds and heat and freshwater fluxes from an atmospheric reanalysis. We find a significant deoxygenation in the northern AS, with O2 inventories north of 20∘ N dropping by over 6 % per decade between 100 and 1000 m. These changes cause an expansion of the OMZ volume north of 20∘ N at a rate of 0.6 % per decade as well as an increase in the volume of suboxia and the rate of denitrification by 14 and 15 % per decade, respectively. We also show that strong interannual and decadal variability modulate dissolved oxygen in the northern AS, with most of the O2 decline taking place in the 1980s and 1990s. Using a set of sensitivity simulations we demonstrate that deoxygenation in the northern AS is essentially caused by reduced ventilation induced by the recent fast warming of the sea surface, including in the Gulf, with a contribution from concomitant summer monsoon wind intensification. This is because, on the one hand, surface warming enhances vertical stratification and increases Gulf water buoyancy, thus inhibiting vertical mixing and ventilation of the thermocline. On the other hand, summer monsoon wind intensification causes a rise in the thermocline depth in the northern AS that lowers O2 levels in the upper ocean. Our findings confirm that the AS OMZ is strongly sensitive to upper-ocean warming and concurrent changes in the Indian monsoon winds. Finally, our results also demonstrate that changes in the local climatic forcing play a key role in regional dissolved oxygen changes and hence need to be properly represented in global models to reduce uncertainties in future projections of deoxygenation.

Vegetation Greening Offsets Urbanization‐Induced Fast Warming in Guangdong, Hong Kong, and Macao Region (GHMR)

AbstractPrevious studies show that the environment in the Guangdong, Hong Kong, and Macao region is under the double stress of global warming and urbanization. Here, we show that due to the increase of regional greenness, the effect of urbanization warming on surface air temperature (SAT) decreased with time and became statistically insignificant from 2004 to 2018, compared to 1979 onward; while the urbanization itself has significantly warmed land surface temperature (LST), with a warming rate of 0.14°C ± 0.04°C/10a at daytime and 0.02°C ± 0.02°C/10a at nighttime during 2004–2018, respectively. The anthropogenic heat was found to have a limited influence on SAT, but more significant and tangible effects on LST. It is essential to improve the control of additional warming effects caused by urbanization.

Long-Term Observations of Interannual and Decadal Variation of Sea Surface Temperature in the Taiwan Strait

Long-term observations of interannual and decadal variation of sea surface temperature (SST) in the Taiwan Strait (TS) were studied for the period 1870–2018; the climatology data were obtained from the Met Office Hadley Centre, UK. In the study period, the highest annual mean and lowest SST observed were 25.3°C in 1998 and 22.4°C in 1919, respectively. Six distinct regimes were identified. The first regime of fairly stable or slightly cooling SST lasted through the 1920s. The two regime shifts of 1919 to 1945 and 1976–1977 to 1998 led to the two fast warming trends of 2.0°C in 26 years, from 22.5°C in 1919 up to 24.5°C in 1945, and of 2.4°C in 22 years, from 22.9°C in 1977 up to 25.3°C in 1998, respectively. Another two regime shifts initiated in 1945 (1945–1976) and 1998–1999 (1998–2011) that led to 1.6°C and 1.0°C cooling, respectively. A recent and fast warming trend with 0.63°C/decade suggested that the warming hiatus from 1998 to 2011 faded away since 2012. The spatial distribution of climate trends through the decades across the TS revealed a strong spatial gradient along the Strait. In the north (southern East China Sea), the magnitude and rate of the overall SST warming between 1870 and 2018 were approximately 1.5 times than those in the south (northern South China Sea).

Nested Recharge Systems in Mountain Block Hydrology: High-Elevation Snowpack Generates Low-Elevation Overwinter Baseflow in a Rocky Mountain River

The majority of each year′s overwinter baseflow (i.e., winter streamflow) in a third-order eastern slopes tributary is generated from annual melting of high-elevation snowpack which is transmitted through carbonate and siliciclastic aquifers. The Little Elbow River and its tributaries drain a bedrock system formed by repeated thrust faults that express as the same siliciclastic and carbonate aquifers in repeating outcrops. Longitudinal sampling over an 18 km reach was conducted at the beginning of the overwinter baseflow season to assess streamflow provenance. Baseflow contributions from each of the two primary aquifer types were apportioned using sulfate, δ34SSO4, and silica concentrations, while δ18OH2O composition was used to evaluate relative temperature and/or elevation of the original precipitation. Baseflow in the upper reaches of the Little Elbow was generated from lower-elevation and/or warmer precipitation primarily stored in siliciclastic units. Counterintuitively, baseflow generated in the lower-elevation reaches originated from higher-elevation and/or colder precipitation stored in carbonate units. These findings illustrate the role of nested flow systems in mountain block recharge: higher-elevation snowmelt infiltrates through fracture systems in the cliff-forming—often higher-elevation—carbonates, moving to the lower-elevation valley through intermediate flow systems, while winter baseflow in local flow systems in the siliciclastic valleys reflects more influence from warmer precipitation. The relatively fast climatic warming of higher elevations may alter snowmelt timing, leaving winter water supply vulnerable to climatic change.

Uneven Warming Likely Contributed to Declining Near‐Surface Wind Speeds in Northern China Between 1961 and 2016

AbstractA decline in mean near‐surface (10 m) wind speed has been widely reported for many land regions over recent decades, yet the underlying cause(s) remains uncertain. This study investigates changes in near‐surface wind speed over northern China from 1961 to 2016, and analyzes the associated physical mechanisms using station observations, reanalysis products and model simulations from the Community Atmosphere Model version 5.1 (CAM5). The homogenized near‐surface wind speed shows a significantly (p < 0.05) decline trend of −0.103 m s−1 decade−1, which stabilized from the 1990s onwards. Similar negative trends are observed for all seasons, with the strongest trends occurring in the central and eastern parts of northern China. Fast warming has occurred at high‐latitudes (i.e., >50°N) in recent decades, which has weakened the annual and seasonal meridional air temperature gradient (−0.33°C to −0.12°C dec−1, p < 0.05, except autumn) between these regions (50°–60°N, 75°–135°E) and the northern China zone (35°–45°N, 75°–135°E). This caused a significant (p < 0.05) decrease in annual and seasonal pressure gradient (−0.43 to −0.20 hPa dec−1) between the two zones, which contributed to the slowdown of winds. CAM5 simulations demonstrate that spatially uneven air temperature increases and near‐surface wind speed decreases over northern China can be realistically reproduced using the so‐called “all forcing” simulation, while the “natural only forcing” simulation fails to realistically simulate the uneven warming patterns and declines in near‐surface wind speed over most of northern China, except for summer.

Earthquakes in the Eastern Canadian Arctic: Past Occurrences, Present Hazard, and Future Risk

AbstractThe Canadian Arctic encompasses several active seismic areas where a small number of significant earthquakes have been recorded since the early twentieth century. Our study area is defined as the eastern Canadian Arctic, an immense territory that covers 30% of the Canadian land mass. It includes the territory of Nunavut and the region of Nunavik in northern Quebec. Ten earthquakes had a moment magnitude (M) between 5.5 and 7.4, but only five can be considered significant because of their impact. Most were felt in communities at distances of a few hundreds of kilometers, but none exceeded modified Mercalli intensity (MMI) V. This article contains descriptions of the impact of these five earthquakes and of smaller ones that were felt in nearby communities. These macroseismic effects suggest stronger attenuation of MMIs than what is generally assumed for eastern North America. According to the current seismic zoning, very few communities face a significant earthquake hazard. Seismic risk has to consider that most high Arctic buildings are built on piles sitting on permafrost. It is believed that the newer engineered constructions would resist fairly well to seismic shaking, as opposed to buildings with older at grade foundations with little lateral resistance. The fast warming of the Arctic may lead to some thickening of the active layer of the permafrost, which may increase the potential for slope instabilities during earthquake shaking. The change would not be significant enough to alter the potential for local ground-motion amplification.

Effect of habitat quality and phenotypic variation on abundance‐ and trait‐based early warning signals of population collapses

Loss of resilience in population numbers in response to environmental perturbations may be predicted with statistical metrics called early warning signals (EWS) that are derived from abundance time series. These signals, however, have been shown to have limited success, leading to the development of trait‐based EWS that are based on information collected from phenotypic traits such as body size. Experimental work assessing the efficacy of EWS under varying ecological and environmental factors are rare. In addition, disentangling how such warning signals are affected under varying ecological and environmental factors is key to their application in biological conservation. Here, we experimentally test how different rates of environmental forcing (i.e. warming) and varying ecological factors (i.e. habitat quality and phenotypic diversity) affected population stability and predictive power of early warning signals of population collapse. We analyzed population density and body size time series data from three phenotypically different populations of a protozoan ciliate Askenasia volvox in two levels of habitat quality subjected to three different treatments of warming (i.e. no warming, fast warming and slow warming). We then evaluated how well abundance‐ and trait‐based EWS predicted population collapses under different levels of phenotypic diversity, habitat quality and warming treatments. Our results suggest that habitat quality and warming treatments had more profound effects than phenotypic diversity had on both population stability and on the performance of abundance‐based signals of population collapse. In addition, trait‐based EWS generally performed well, were reliable and more robust in forecasting population collapse than abundance‐based EWS, regardless of variation in environmental and ecological factors. Our study points towards the development of a predictive framework that includes information from phenotypic traits such as body size as an indicator of loss of resilience of ecological systems in response to environmental perturbations.

Long‐term evolution of global sea surface temperature trend

AbstractThe ocean plays an essential role in regulating global and regional climate, which is mainly achieved through sea surface temperature anomaly (SSTA) changes. Studies on global sea surface temperature (GSST) are primarily carried out under linear assumption, which is not capable of fully revealing the evolution characteristics of sea surface temperature (SST) due to the non‐linear and non‐stationary nature of the SST. Here, the evolution of the GSST trend in the past century is investigated by using an adaptive and local spatial–temporally multidimensional ensemble empirical mode decomposition method. The results show that the global ocean has been warming except for the subpolar North Atlantic, the equatorial central Pacific, and the Southern Ocean in the Pacific sector. The equatorial central Pacific turned from cooling to warming around the middle of the last century made it one of the fastest‐warming regions in recent decades with other regions located in the Arctic Ocean and the western‐boundary current regions and their mid‐latitude extensions in both hemispheres. The strongest warming during recent decades is found in the Arctic Ocean, east of the continents in the northern hemisphere, the entire Indian Ocean, and especially in the tropical Pacific Ocean. From a zonal average perspective, warming (>0.1 K since 1900) first took place in the subtropical regions of the Northern Hemisphere and 50°S of the Southern Hemisphere almost simultaneously around 1910, then followed by the subpolar warming in the Northern Hemisphere. The first two bands of warming both expanded equatorward leading to the fast warming of tropical oceans, especially for the Pacific Ocean.

Photothermal conversion of gold nanoparticles for fast and uniform laser warming of vitrified biomaterials

Photothermal conversion of gold nanoparticles for fast and uniform laser warming of vitrified biomaterials

Testing multiple drivers of the temperature‐size rule with nonlinear temperature increase

Abstract The temperature‐size rule (TSR) describes the inverse relationship between organism size and environmental temperature in uni‐ and multicellular species. Despite the TSR being widespread, the mechanisms for shrinking body size with warming remain elusive. Here, we experimentally test three hypotheses (differential development and growth [DDG], maintain aerobic scope and regulate oxygen supply [MASROS] and the supply–demand [SD] hypothesis) potentially explaining the TSR using the aquatic protist Colpidium striatum in three gradually changing and one constant temperature environment crossed with three different nutrient levels. We find that the constant and slowly warming environments show similar responses in terms of population dynamics, whereas populations with linear and fast warming quickly decline and show a stronger temperature‐size response. Our analyses suggest that acclimation may have played a role in observing these differences among treatments. The SD hypothesis is most parsimonious with the data, however, neither the DDG nor the MASROS hypothesis can be firmly dismissed. We conclude that the TSR is driven by multiple ecological and acclimatory responses, hence multicausal. A free Plain Language Summary can be found within the Supporting Information of this article.

Fast Climate Responses to Aerosol Emission Reductions During the COVID‐19 Pandemic

AbstractThe reduced human activities and associated decreases in aerosol emissions during the COVID‐19 pandemic are expected to affect climate. Assuming emission changes during lockdown, back‐to‐work and post‐lockdown stages of COVID‐19, climate model simulations show a surface warming over continental regions of the Northern Hemisphere. In January–March, there was an anomalous warming of 0.05–0.15 K in eastern China, and the surface temperature increase was 0.04–0.07 K in Europe, eastern United States, and South Asia in March–May. The longer the emission reductions undergo, the warmer the climate would become. The emission reductions explain the observed temperature increases of 10–40% over eastern China relative to 2019. A southward shift of the ITCZ is also seen in the simulations. This study provides an insight into the impact of COVID‐19 pandemic on global and regional climate and implications for immediate actions to mitigate fast global warming.

Fast Warming Has Accelerated Snow Cover Loss during Spring and Summer across the Northern Hemisphere over the Past 52 Years (1967–2018)

With snow cover changing worldwide in several worrisome ways, it is imperative to determine both the variability in snow cover in greater detail and its relationship with ongoing climate change. Here, we used the satellite-based snow cover extent (SCE) dataset of National Oceanic and Atmospheric Administration (NOAA) to detect SCE variability and its linkages to climate over the 1967–2018 periods across the Northern Hemisphere (NH). Interannually, the time series of SCE across the NH reveal a substantial decline in both spring and summer (−0.54 and −0.71 million km2/decade, respectively), and this decreasing trend corresponded with rising spring and summer temperatures over high-latitude NH regions. Among the four seasons, the temperature rise over the NH was the highest in winter (0.39 °C/decade, p < 0.01). More precipitation in winter was closely related to an increase of winter SCE in mid-latitude areas of NH. Summer precipitation over the NH increased at a significant rate (1.1 mm/decade, p < 0.01), which likely contribute to the accelerated reduction of summer’s SCE across the NH. However, seasonal sensitivity of SCE to temperature changes differed between the Eurasian and North American continents. Thus, this study provides a better understanding of seasonal SCE variability and climatic changes that occurred at regional and hemispheric spatial scales in the past 52 years.

Arctic River Dissolved and Biogenic Silicon Exports—Current Conditions and Future Changes With Warming

AbstractSilicon (Si) exports from terrestrial to marine systems can dictate phytoplankton species composition in Arctic coastal waters. Diatoms are often the dominant autotroph in Arctic waters, making Si an important control on Arctic marine primary productivity. Yet even as Arctic regions are among the fastest warming on Earth, we lack baseline knowledge on the magnitudes and controls of Arctic river Si exports. To address uncertainties in current and future Si behavior, we used a combination of field data and modeling to quantify daily yields of dissolved Si (DSi) and biogenic Si (BSi) from a 400 km space‐for‐time latitudinal gradient of seven basins across the boreal‐Arctic transition in Alaska (United States) over the course of 2 years (2015–2016). Mean annual DSi concentrations (33–149 μM) and yields (13–49 kmol km−2 year−1) were significantly and positively correlated with mean basin active layer depth, indicating that permafrost thaw will likely increase DSi fluxes to Arctic coastal waters. Conversely, BSi concentrations (7–16 μM) and yields (2.6–4.5 kmol km−2 year−1) were more uniform across the seven basins, indicating that warming may not substantially alter BSi loads to coastal systems in the near future. Our data also indicate that climatic warming will advance the timing of Si delivery to coastal waters in the spring, although the ratios of Si to nitrogen in Arctic river exports will likely remain steady. These results highlight the important role of basin hydrology, largely driven by permafrost extent, as a key driver of Si exchange at the land‐sea interface in the Arctic.

Time-evolving sea-surface warming patterns modulate the climate change response of subtropical precipitation over land

Greenhouse gas (GHG) emissions affect precipitation worldwide. The response is commonly described by two timescales linked to different processes: a rapid adjustment to radiative forcing, followed by a slower response to surface warming. However, additional timescales exist in the surface-warming response, tied to the time evolution of the sea-surface-temperature (SST) response. Here, we show that in climate model projections, the rapid adjustment and surface mean warming are insufficient to explain the time evolution of the hydro-climate response in three key Mediterranean-like areas-namely, California, Chile, and the Mediterranean. The time evolution of those responses critically depends on distinct shifts in the regional atmospheric circulation associated with the existence of distinct fast and slow SST warming patterns. As a result, Mediterranean and Chilean drying are in quasiequilibrium with GHG concentrations, meaning that the drying will not continue after GHG concentrations are stabilized, whereas California wetting will largely emerge only after GHG concentrations are stabilized. The rapid adjustment contributes to a reduction in precipitation, but has a limited impact on the balance between precipitation and evaporation. In these Mediterranean-like regions, future hydro-climate-related impacts will be substantially modulated by the time evolution of the pattern of SST warming that is realized in the real world.

Investigation of the relationship between fractal and hydraulic properties of porous structures of the upper respiratory tract of some Arctic animals

The respiratory ducts of animals and humans are presented by curved tubes with complex geometries. The open areas in such structures are filled with moving air governed by a pressure drop between the inlet and outlet of the duct. The complex structures formed by thin walls and warmed by constant blood flow at the body temperatures T=36-39 C serve for fast and efficient warming of the inhaled air to the body temperature and its moistening up to 100% humidity. The Arctic animals possess the most efficient nasal ducts allowing the heating of the inhaled air from T=-30-60C to T=38-39 C during the duct with the length L=8-15 only. The detailed geometry of the nasal ducts of some Arctic animal has been studied on the computed tomograms (CT) scans of the heads of the animals found in the open databases and published in literature. The highly porous structures on some slices are formed by fractal-like divisions of the walls protruded into the nasal lumen. Since the fractal structures are characterized by their fractal dimensions D, the relationships between the hydrodynamic properties and fractal dimensions of the porous structures of the upper respiratory tract of some Arctic animals has been studied. The dimensions D of the cross sections of the tract have been calculated by the counting box method. The porosities of the samples, the tortuosity of the pores, and the equivalent hydraulic diameter Dh of the channel have been calculated. Sierpinski fractals of various types have been used as models of porous structures, for which the above listed parameters, as well as hydraulic resistance to a stationary flow, have also been computed. A number of statistical dependencies between the calculated parameters were revealed, but the absence of their correlations with D was shown. It was obtained, the structures with different porosities and hydraulic resistance Dh can have the same values ​​of D. Therefore, the choice of an adequate model based on only D value introduces significant errors in the calculations of air heating along the upper respiratory tract. The statistical dependences inherent in the natural samples studied can be obtained only on the basis of multifractal models in which the number and shape of the channels, as well as the scale of their decrease, change in a certain way at each generation.

Climate variability reduces employment in New England fisheries

Climate change is already affecting fish productivity and distributions worldwide, yet its impact on fishing labor has not been examined. Here I directly link large-scale climate variability with fishery employment by studying the effects of sea-surface pressure changes in the North Atlantic region, whose waters are among the world's fastest warming. I find that climate shocks reduce not only regional catch and revenue in the New England fishing sector, but also ultimately county-level wages and employment among commercial harvesters. Each SD increase from the climatic mean decreases county-level fishing employment by 13%, on average. The South Atlantic region serves as a control due to its different ecological response to climate. Overall, I estimate that climate variability from 1996 to 2017 is responsible for a 16% (95% CI: 10% to 22%) decline in county-level fishing employment in New England, beyond the changes in employment attributable to management or other factors. This quantitative evidence linking climate variability and fishing labor has important implications for management in New England, which employs 20% of US commercial harvesters. Because the results are mediated by the local biology and institutions, they cannot be directly extrapolated to other regions. But they show that climate can impact fishing outcomes in ways unaccounted by management and offer a template for study of this relationship in fisheries around the world.

Impact of internal variability on climate change for the upcoming decades: analysis of the CanESM2-LE and CESM-LE large ensembles

The pace of climate change can have a direct impact on the efforts required to adapt. For short timescales, however, this pace can be masked by internal variability (IV). Over a few decades, this can cause climate change effects to exceed what would be expected from the greenhouse gas (GHG) emissions alone or, to the contrary, cause slowdowns or even hiatuses. This phenomenon is difficult to explore using ensembles such as CMIP5, which are composed of multiple climate models and thus combine both IV and inter-model differences. This study instead uses CanESM2-LE and CESM-LE, two state-of-the-art large ensembles (LE) that comprise multiple realizations from a single climate model and a single GHG emission scenario, to quantify the relationship between IV and climate change over the next decades in Canada and the USA. The mean annual temperature and the 3-day maximum and minimum temperatures are assessed. Results indicate that under the RCP8.5, temperatures within most of the individual large ensemble members will increase in a roughly linear manner between 2021 and 2060. However, members of the large ensembles in which a slowdown of warming is found during the 2021–2040 period are two to five times more likely to experience a period of very fast warming in the following decades. The opposite scenario, where the changes expected by 2050 would occur early because of IV, remains fairly uncommon for the mean annual temperature, but occurs in 5 to 15% of the large ensemble members for the temperature extremes.

Fast deep water warming of a subtropical crater lake.

Water temperature of deep lakes is often used to evaluate climate variability over long periods. Santa Maria del Oro Lake is a sub-tropical crater-lake (60 m maximum depth) almost confined by surrounding mountains, which only receives seasonal fresh water input. In order to evaluate lake thermal variations, we measured water temperatures at bottom, 4 m, 10 m, 25 m, and 32 m depth. To study lake vertical mixing process, we implemented a 3D high-resolution model forced with atmospheric variables. Field data analysis indicate an hypolimnetic warming rate of 0.1136 ± 0.0001 °C y-1, about ten times larger than the mean global warming rate, and model results indicated that this was mainly caused by thermal diffusion between surface and bottom water layers. The lake presents a stable temperature stratification, which can reach 40 m depth during the windiest and coolest nights, indicating that the lake is oligomictic (i.e. mixes only occasionally). Inter-annual climate variability and global warming can alter the frequency of full vertical water mixing and, therefore, deep water warming. The used methodology can be useful to evaluate bottom trend temperature of subtropical lakes worldwide, and results may contribute to the use of deep lake waters as sentinels of multi-annual climate variability. As deep water mixing affects water quality, this may also be useful to better manage lake environmental services.

Sunshine as culprit: It induces early spring physiological drought in dark coniferous (Pinus sibirica and Abies sibirica) alpine forest

Trees comprising high mountain forests have different requirements for site conditions (such as the water supply), thus current climate warming leads to varying reactions of upper forest boundaries depending on the site conditions and ecophysiological features of species. Positive reactions to an increasing heat supply during vegetative season may be hindered for drought-sensitive species by a water deficit in a cold environment, particularly during late winter or early spring.We investigated the radial growth of dark coniferous forest species Siberian stone pine (Pinus sibirica Du Tour) and Siberian fir (Abies sibirica Ledeb.) growing on slopes of different orientation (south-west, east, and north) near the upper forest boundary in an area undergoing fast climate warming: the Western Sayan Mountains (South Siberia, Russia), near a massive water reservoir. Correlations of tree-ring width chronologies with moving 21-day temperature series were used to more precisely determine the timing of temperature influence; an analysis of extreme and optimal years and multifactor regression modeling were applied to assess the most favorable/unfavorable thermal conditions in the study area and to estimate the tree growth reaction to the current climatic trends, respectively.Despite relatively low variation in growth (standard deviation <0.2), a significant common climatic signal in tree-ring width was found at all sampling sites. On the shaded northern slopes, P. sibirica is only mildly limited by summer temperatures and has a low similarity (correlations and synchronicity of extreme/optimal years) with other sites. Conversely, the growth of A. sibirica and P. sibirica on two sunlit slopes is similar (r = 0.44–0.81) and has a common pattern of regulation by temperatures before (r = −0.17…−80.40; April 3 – May 4 on average) and more significantly during vegetative season (r = 0.31…0.44; May 17 – August 27 on average). We hypothesize that both species, being drought-sensitive, undergo water stress in the early spring, and exposition of previous years’ needles to severe temperature variation may lead to partial defoliation and xylem embolism, thus suppressing growth. The patterns of climatic response and species distribution on slopes indicate that A. sibirica is more sensitive to this physiological drought and needs gentler slopes than P. sibirica.Temperature increase in the study area during the last decades have occured about five times faster in the early spring (being enhanced by the reservoir) than in summer. This combination of spring and summer warming leads to an increase in P. sibirica radial growth on the northern slope and the stable growth of both species on sunlit slopes, i.e. providing a tentatively optimistic assessment of the dark coniferous forests’ near future in the region.

Krill (Euphausia superba) distribution contracts southward during rapid regional warming

High-latitude ecosystems are among the fastest warming on the planet1. Polar species may be sensitive to warming and ice loss, but data are scarce and evidence is conflicting2–4. Here, we show that, within their main population centre in the southwest Atlantic sector, the distribution of Euphausia superba (hereafter, ‘krill’) has contracted southward over the past 90 years. Near their northern limit, numerical densities have declined sharply and the population has become more concentrated towards the Antarctic shelves. A concomitant increase in mean body length reflects reduced recruitment of juvenile krill. We found evidence for environmental controls on recruitment, including a reduced density of juveniles following positive anomalies of the Southern Annular Mode. Such anomalies are associated with warm, windy and cloudy weather and reduced sea ice, all of which may hinder egg production and the survival of larval krill5. However, the total post-larval density has declined less steeply than the density of recruits, suggesting that survival rates of older krill have increased. The changing distribution is already perturbing the krill-centred food web6 and may affect biogeochemical cycling7,8. Rapid climate change, with associated nonlinear adjustments in the roles of keystone species, poses challenges for the management of valuable polar ecosystems3. As the southwest Atlantic sector of the Southern Ocean has warmed, the distribution of a key species, Antarctic krill, has contracted southwards. This has occurred in tandem with a decline in recruitment of juveniles, linked to increasingly positive anomalies of the Southern Annular Mode.