Latitudinal Temperature Gradient Research Articles

Пространственная реконструкция климата востока Азии в раннем эоцене

Using the Coexistence Approach, climatic zones were identified for the Early Eocene of East Asia. Data for reconstruction include 48 palynofloras from the East Asia's Lower Eocene continental deposits from 75° to 19° N. The climatic inferences obtained are consistent with global trends, showing high values of mean annual temperature (MAT) and mean annual precipitation (MAP). According to our results, there is a weakly expressed latitudinal temperature gradient from the north to the south, showing an increasing trend for MAT values, while a very weakly expressed latitudinal gradient of precipitation demonstrates a decreasing trend for MAP values. Based on MAT and MAP values, three regional climatic zones are distinguished. The warm moderate climate zone (north of ≈ 55° paleolatitude) is characterized by low values for temperature (14.2-16.2 °C) and high ones for precipitation (1158-1334 mm). In the transition zone (≈ 45-55° paleolatitude), MAT values vary from 15.9 to 19.0 °C, and MAP values range from 874 to 1352 mm. The subtropical climate zone (south of ≈ 45° paleolatitude) is characterized by high values for temperature (16.5-19.1 °C) and low, for precipitation (874-1263 mm).

Regional impacts of warming on biodiversity and biomass in high latitude stream ecosystems across the Northern Hemisphere

Warming can have profound impacts on ecological communities. However, explorations of how differences in biogeography and productivity might reshape the effect of warming have been limited to theoretical or proxy-based approaches: for instance, studies of latitudinal temperature gradients are often conflated with other drivers (e.g., species richness). Here, we overcome these limitations by using local geothermal temperature gradients across multiple high-latitude stream ecosystems. Each suite of streams (6-11 warmed by 1-15°C above ambient) is set within one of five regions (37 streams total); because the heating comes from the bedrock and is not confounded by changes in chemistry, we can isolate the effect of temperature. We found a negative overall relationship between diatom and invertebrate species richness and temperature, but the strength of the relationship varied regionally, declining more strongly in regions with low terrestrial productivity. Total invertebrate biomass increased with temperature in all regions. The latter pattern combined with the former suggests that the increased biomass of tolerant species might compensate for the loss of sensitive species. Our results show that the impact of warming can be dependent on regional conditions, demonstrating that local variation should be included in future climate projections rather than simply assuming universal relationships.

Bayesian multi-proxy reconstruction of early Eocene latitudinal temperature gradients

Abstract. Accurately reconstructing large-scale palaeoclimatic patterns from sparse local records is critical for understanding the evolution of Earth's climate. Particular challenges arise from the patchiness, uneven spatial distribution, and disparate nature of palaeoclimatic proxy records. Geochemical data typically provide temperature estimates via transfer functions derived from experiments. Similarly, transfer functions based on the climatic requirements of modern taxa exist for some fossil groups, such as pollen assemblages. In contrast, most ecological and lithological data (e.g. coral reefs and evaporites) only convey information on broad climatic requirements. Historically, most large-scale proxy-based reconstructions have used either geochemical or ecological data, but few studies have combined multiple proxy types into a single quantitative reconstruction. Large spatial gaps in existing proxy records have often been bridged by simple averaging, without taking into account the spatial distribution of samples, leading to biased temperature reconstructions. Here, we present a Bayesian hierarchical model to integrate ecological data with established geochemical proxies into a unified quantitative framework, bridging gaps in the latitudinal coverage of proxy data. We apply this approach to the early Eocene climatic optimum (EECO), the interval with the warmest sustained temperatures of the Cenozoic. Assuming the conservation of thermal tolerances of modern coral reefs and mangrove taxa, we establish broad sea surface temperature ranges for EECO coral reef and mangrove sites. We integrate these temperature estimates with the EECO geochemical shallow marine proxy record to model the latitudinal sea surface temperature gradient and global average temperatures of the EECO. Our results confirm the presence of a flattened latitudinal temperature gradient and unusually high polar temperatures during the EECO, which is supported by high-latitude ecological data. We show that integrating multiple types of proxy data, and adequate prior information, has the potential to enhance quantitative palaeoclimatic reconstructions, improving temperature estimates from datasets with limited spatial sampling.

Variation in functional composition of reef fishes along a tropical‐to‐temperate gradient

AbstractAimsTransformation of species and functional composition on subtropical reefs are ongoing due to poleward range shifts of some tropical species, with largely unknown consequences to ecosystem functioning. Trait‐based approaches are powerful tools to quantify such changes. Here, we evaluated changes in the trait composition of coral‐associated fish assemblages along a tropical‐to‐temperate environmental gradient of ca. 1400 km in southern Japan with abundance‐weighted trait expression to assess how trait composition changes with increasing latitude.LocationRyukyu Islands and southern Pacific coast of Japan.TaxonReef fish.MethodsWe tested for shifts in trait space and functional redundancy, based on five morphological, life history and behavioural traits: maximum length, pelagic larval duration, trophic level, substrate preference and reproductive mode. Our trait database was coded with two approaches, first, by attributing a single value to each trait per species, and second, by fuzzy coding that allows more than one value per trait and hence considers some intraspecific trait variation.ResultsWe found a reduction in specialist habitat traits (coral substrate preference, nesters and herbivores) and an increase in generalist traits (predators) with increasing latitude, along with a contraction in trait space from tropical‐to‐temperate reefs. Functional redundancy declined with increasing latitude. These trends were closely linked with latitudinal gradients in temperature, along with changes in other environmental factors such as turbidity and photosynthetically active radiation.Main ConclusionFunctional turnover and contractions are thus likely due to the marginal conditions for coral‐associated fishes at higher latitudes, favouring generalist species, whereas increased resources at lower latitudes favour high redundancy and niche partitioning. Accounting for intraspecific trait variation indicated the same trends but highlighted increased functional vulnerability across all sites. We show that trait complexity in coral‐associated fish communities decreases from tropical‐to‐temperate reefs, highlighting the reduced functional scope that comes with marginal environmental conditions.

Comparison of UKESM1 and CESM2 simulations using the same multi-target stratospheric aerosol injection strategy

Abstract. Solar climate intervention using stratospheric aerosol injection (SAI) has been proposed as a method which could offset some of the adverse effects of global warming. The Assessing Responses and Impacts of Solar climate intervention on the Earth system with Stratospheric Aerosol Injection (ARISE-SAI) set of simulations is based on a moderate-greenhouse-gas-emission scenario and employs injection of sulfur dioxide at four off-equatorial locations using a control algorithm which maintains the global-mean surface temperature at 1.5 K above pre-industrial conditions (ARISE-SAI-1.5), as well as the latitudinal gradient and inter-hemispheric difference in surface temperature. This is the first comparison between two models (CESM2 and UKESM1) applying the same multi-target SAI strategy. CESM2 is successful in reaching its temperature targets, but UKESM1 has considerable residual Arctic warming. This occurs because the pattern of temperature change in a climate with SAI is determined by both the structure of the climate forcing (mainly greenhouse gases and stratospheric aerosols) and the climate models' feedbacks, the latter of which favour a strong Arctic amplification of warming in UKESM1. Therefore, research constraining the level of future Arctic warming would also inform any hypothetical SAI deployment strategy which aims to maintain the inter-hemispheric and Equator-to-pole near-surface temperature differences. Furthermore, despite broad agreement in the precipitation response in the extratropics, precipitation changes over tropical land show important inter-model differences, even under greenhouse gas forcing only. In general, this ensemble comparison is the first step in comparing policy-relevant scenarios of SAI and will help in the design of an experimental protocol which both reduces some known negative side effects of SAI and is simple enough to encourage more climate models to participate.

A Millennial‐Scale Oscillation in Latitudinal Temperature Gradients Along the Western North Atlantic During the Mid‐Holocene

AbstractChanges in vegetation in North America indicate Holocene shifts in the latitudinal temperature gradient along the western margin of the North Atlantic. Tree taxa such as oak (Quercus) and birch (Betula) experienced opposing directions of change across different latitudes consistent with changes in temperature gradient steepness. Pollen‐inferred temperatures from 34 sites quantify the gradient changes and reconstruct a long‐term northward steepening in summer and southward steepening in winter. From 4.8 to 3.8 ka, an oscillation in tree distributions interrupted the long‐term trends as a steep temperature gradient developed north of 43.5°N. The shift likely limited cold outbreaks to the south, producing anomalously high summer temperatures at 42–43.5°N, and enabling a northward expansion of oak forests. The forest and temperature gradient changes appear consistent with orbital and ice sheet forcing as well as millennial variability in the North Atlantic pressure field analogous to the North Atlantic Oscillation on interannual time scales.

The functional mechanism behind the latitudinal pattern of liana diversity: Freeze-thaw embolism reduces the ecological performance of liana species.

There is a strong decrease in liana diversity along latitudinal and altitudinal gradients at a global scale, and there is a marked difference in liana diversity between tropical and temperate ecosystems. From these observations, it has been proposed that cold temperatures would restrict the ecological patterns of liana because of their vascular system's vulnerability to freeze-thaw embolism. Our objective was to establish the functional mechanism that drives the loss of liana diversity along a latitudinal temperature gradient. We evaluate the ecological performance of liana in 10 different species based on the apical growth rate, as well as functional traits associated with efficiency (maximum hydraulic conductivity and percentage conductivity lost) and safety of water transport (vessel diameter, vessel density, wood density, and root pressure). We found that at the colder (more southern) site within the latitudinal gradient, liana species showed lower performance, with a fivefold decrease in their apical growth rate as compared to the warmer (more northern) sites. We postulate that this lower performance results from a much lower water transport efficiency (26.1-fold decrease as compared to liana species that inhabit warmer sites) that results from higher freeze-thaw (37.5% of PLC) and reduction of vessel diameter (3 times narrower). These results are unmistakable evidence that cold temperature restricts liana performance: in a cold environment, liana species exhibit a strong decrease in performance, low efficiency, and higher safety of water transport. Conversely, at warmer sites, we found that liana species exhibit functional strategies associated with higher performance, higher efficiency, and lower safety of water transport capacity. This trade-off between efficiency and safety of water transport and their effects on performance could explain the latitudinal pattern of liana diversity.

Saturn's Atmosphere in Northern Summer Revealed by JWST/MIRI

AbstractSaturn's northern summertime hemisphere was mapped by JWST/Mid‐Infrared Instrument (4.9–27.9 µm) in November 2022, tracing the seasonal evolution of temperatures, aerosols, and chemical species in the 5 years since the end of the Cassini mission. The spectral region between reflected sunlight and thermal emission (5.1–6.8 µm) is mapped for the first time, enabling retrievals of phosphine, ammonia, and water, alongside a system of two aerosol layers (an upper tropospheric haze p < 0.3 bars, and a deeper cloud layer at 1–2 bars). Ammonia displays substantial equatorial enrichment, suggesting similar dynamical processes to those found in Jupiter's equatorial zone. Saturn's North Polar Stratospheric Vortex has warmed since 2017, entrained by westward winds at p < 10 mbar, and exhibits localized enhancements in several hydrocarbons. The strongest latitudinal temperature gradients are co‐located with the peaks of the zonal winds, implying wind decay with altitude. Reflectivity contrasts at 5–6 µm compare favorably with albedo contrasts observed by Hubble, and several discrete vortices are observed. A warm equatorial stratospheric band in 2022 is not consistent with a 15‐year repeatability for the equatorial oscillation. A stacked system of windshear zones dominates Saturn's equatorial stratosphere, and implies a westward equatorial jet near 1–5 mbar at this epoch. Lower stratospheric temperatures, and local minima in the distributions of several hydrocarbons, imply low‐latitude upwelling and a reversal of Saturn's interhemispheric circulation since equinox. Latitudinal distributions of stratospheric ethylene, benzene, methyl, and carbon dioxide are presented for the first time, and we report the first detection of propane bands in the 8–11 µm region.

Biogeographic barriers and historic climate shape the phylogeography and demography of the common gartersnake

AbstractAimCurrent distributions of widespread North American (NA) species have been shaped by Pleistocene glacial cycles, latitudinal temperature gradients, sharp longitudinal habitat transitions and the vicariant effects of major mountain and river systems that subdivide the continent. Within these transcontinental species, genetic diversity patterns might not conform to established biogeographic breaks compared to more spatially restricted taxa due to intrinsic differences or spatiotemporal differences. In this study, we highlight the effects of these extrinsic variables on genetic structuring by investigating the phylogeographic history of a widespread generalist squamate found throughout NA.LocationNorth America.TaxonCommon gartersnake, Thamnophis sirtalis.MethodsWe evaluate the effects of major river basins and the forest‐grassland transition into the Interior Plains on genetic structure patterns using phylogenetic, spatially informed population structure and demographic analyses of single nucleotide polymorphism data and address range expansion history with ecological niche modelling using locality and historic climate data.ResultsWe identify four phylogeographic lineages with varying degrees of connectivity between them. We find discordant population structure patterns between sex‐linked and autosomal loci with respect to the relationship between the central NA lineage relative to coastal lineages. We find support for southeast Pleistocene refugia where recent secondary contact occurred during the Last Glacial Maximum and evidence for both northern and southern refugia in western NA.Main ConclusionOur results provide strong evidence for a Pliocene origin for T. sirtalis in central‐southeastern NA preceding its rapid expansion across the continent prior to middle Pleistocene climate‐mediated lineage formation. We implicate major riverine networks within the Mississippi watershed in likely repeated westward expansion events across the Interior Plains. Finally, we corroborate prior conclusions that phenotypic differences between subspecies do not reflect shared evolutionary history and note that the degree of separation between inferred lineages warrants further investigation before any taxonomic revisions are proposed.

Assessing the feasibility of assisted migration of corals in the Red Sea

Climate change, and in particular the unprecedented rapid global warming, presents a major threat to corals, with warming rates potentially exceeding the adaptive capacities of most coral species. Assisted gene flow, the human facilitated introduction of temperature resilience alleles from warmer to threatened colder populations via the movement of individuals (assisted migration) or their gametes (selective breeding), has been suggested as a tool to transfer thermal adaptations among populations. Due to its strong latitudinal temperature gradient and extreme temperature conditions, the Red Sea constitutes an ideal location to investigate the potential of this strategy. Here, we relocated Porites lobata colonies from three reefs along the Saudi Arabian Red Sea with different mean sea surface temperature summer maxima (ranging from 30.9 °C in Duba, 32.5 °C in Thuwal, to 33.8 °C in Jazan) to a common garden experiment in the intermediate central location. Five colonies from each location were fragmented and deployed in situ in early summer of 2018 to investigate physiological differences in bleaching, survival, and growth. Results showed significantly higher bleaching in fragments from Duba, followed by 65% mortality. Even though no bleaching was observed in fragments from Jazan, mortality rates of around 20% indicated that other environmental parameters besides temperature might influence coral health and survival. These results suggest that assisted gene flow via translocation alone may be restricted in its success due to a lack of local adaptations to environmental conditions other than temperature. However, strategies like inter-populational breeding may overcome these limitations as they might allow producing offspring with both increased thermal tolerance and local adaptations.

Global Synthesis of Regional Holocene Hydroclimate Variability Using Proxy and Model Data

AbstractSubstantial changes in terrestrial hydroclimate during the Holocene are recorded in geological archives and simulated by computer models. To identify spatial and temporal patterns during the past 12 ka, proxy records sensitive to changing precipitation and effective moisture (precipitation minus evaporation) were compiled from across the globe (n = 813). Proxy composite timeseries were computed for 30 of the IPCC AR6 regions and compared to two full‐Holocene transient model simulations (TraCE‐21ka and HadCM3) and twelve mid‐Holocene CMIP6 simulations. We find that throughout Northern Hemisphere monsoon regions, proxy and model simulations indicate wetter‐than‐modern conditions during the early and mid‐Holocene while Southern Hemisphere monsoon regions were drier. This insolation driven trend toward modern values began approximately 6,000 years ago, and the clear agreement among proxy records and models may reflect the large magnitude of precipitation change and consistent atmospheric circulation forcing mechanism for these regions. In the midlatitudes, the pattern of change is less certain. Generally, proxy composites show a wetting trend throughout the Holocene for the northern midlatitudes, possibly due to strengthening westerlies from an increasing latitudinal temperature gradient. However, simulations indicate that the magnitude of change was relatively low, and for portions of North America, there is a proxy‐model disagreement. At high latitudes, hydroclimate is positively correlated with temperature in both proxies and models, consistent with projected wetting as temperatures rise. Overall, this large proxy database reveals a coherent pattern of hydroclimate variability despite the challenges associated with reconstructing hydroclimate fields.

Semi-empirical model of the spatiotemporal surface temperature distribution on the plain part of Ukraine

The spatial variation of temperature is found to depend linearly on climate continentality, morphology of the relief, the position of the site with respect to seas, in addition to the usual elevation, latitude and longitude predictors. There are other factors that can have an additional significant influence: big bodies of water, terrain attributes relief, atmospheric factors (local circulation), configuration and aspect of coasts and vegetation. Therefore, these multifactorial influences form the climatic field of temperature.
 In this study, the regional semi—empirical model of the spatiotemporal distribution of the average annual and monthly temperature for the plain part of Ukraine on the basis of the methodology for assessing the influence of height above sea level and geographic coordinates is proposed. Based on the method for determining the altitudinal, latitudinal, and longitudinal gradients of meteorological parameters, we calculated these gradients for annual and monthly air surface temperature for the periods 1961—1990 and 1991—2020.
 Thus, on the plain part of Ukraine, the annual surface air temperature decreases by an average on 0.60—0.63 °C with a shift of 100 m height above sea level, on 0.51—0.55 °C with a shift of one latitude degree to the north, on 0.067—0.071 °C with a shift of one longitude degree to the east. Also, the variations of these annual mean temperature gradients from year to year over the period 1991—2020 are characteristic.
 The seasonal variation of gradients has a pronounced non—monotonic character: highest values of altitudinal gradientare typical for July—August (from –0.63 to –0.73 °C per 100 m), and the lowest values — for April—May (from –0.45 to –0.55 °C per 100 m); highest values of latitudinal gradient are typical for August—September (from –0.60 to –0.70 °С per 1 °N), and the lowest values — for April—May (from –0.20 to –0.35 °С per 1° N); the longitudinal gradients have positive values in June—August (0.074—0.128 °C per 1° E), and negative values in November—March (from –0.228 to –0.154 °C per 1° E).
 We found that the altitudinal and latitudinal gradients of temperature have the most spatiotemporal variability and the longitudinal gradient has the smallest one. Greatest variabilities of temperature gradient values are typical for February—March and July—September, and the least variability — for April—May.
 The analysis of the dynamics of gradient changes in the period 1991—2020 compared to the period 1961—1991 showed the following: the altitudinal gradientvalues increased by 8—13 %. in January and March—May; the latitudinal gradient values increased by ~30 % in December—February and decreased by ~20 % in May—August.
 The proposed semi—empirical model contains a coefficient that takes into account influence of additional effects associated with pronounced orographic and other terrain features. This study presents the numerical values of this coefficient for some specific microclimate regions of the plain part of Ukraine.
 The model estimates of thirty—year monthly mean temperature in Ukraine for the periods 1961—1990 and 1991—2020was calculated. A comparison of the model estimates of of the average annual and monthly temperature for 72 meteostations in Ukraine with their actual values showed a statistically significant correlation (the reliability of the linear approximation is 0.89—0.98). Thus, the presented design of the semi-empirical model makes it possible to quite well restore the annual and monthly temperature on the territory of Ukraine

When bioregionalisation emphasises the presence of vulnerable marine ecosystem indicator species in Nephrops fishing grounds: Evidence in the Bay of Biscay/Irish Sea continuum

Under the apparent homogeneity of soft-bottom ecosystems hides an heterogeneity of habitats driven by variations in sediment composition and environmental conditions.Using an extensive underwater video survey dataset, we explored the taxonomic diversity of soft-bottom Nephrops fishing grounds and their environmental drivers on a large latitudinal scale from the Bay of Biscay to the Irish Sea (Northeast Atlantic). Biogeographical network clustering highlighted indicator species of the different communities and a Between-Class Analysis characterised the abiotic factors influencing each community.Our analyses confirmed a biogeographical limit between the Bay of Biscay and the northern areas driven by a latitudinal temperature gradient and highlighting the distribution of Lusitanian and Boreal species. Mobile fish and crustaceans, and sessile filter-feeder assemblages differed along a depth, bottom current and fishing gradient. Some species assemblages covered the whole latitudinal range, implying a greater influence of optimal environmental surroundings rather than their geographical position. Vulnerable Marine Ecosystem indicator taxa such as Virgularia mirabilis and Pennatula phosphorea are potential indicator species of some clusters, while harvested species such as Nephrops norvegicus or mobile fish characterized other bioregions.Spatial knowledge produced in this study could be integrated as biodiversity layers together with fisheries activities layers in decision support tools such as Marine Spatial Planning in order to define compromise between conservational and fishing objectives. Outcomes of management scenarios would then consider the whole species stock (e.g. Nephrops) rather that local populations independently.

Lipid-biomarker-based sea surface temperature record offshore Tasmania over the last 23 million years

Abstract. The Neogene (23.04–2.58 Ma) is characterised by progressive buildup of ice volume and climate cooling in the Antarctic and the Northern Hemisphere. Heat and moisture delivery to Antarctica is, to a large extent, regulated by the strength of meridional temperature gradients. However, the evolution of the Southern Ocean frontal systems remains scarcely studied in the Neogene. Here, we present the first long-term continuous sea surface temperature (SST) record of the subtropical front area in the Southern Ocean at Ocean Drilling Program (ODP) Site 1168 off western Tasmania. This site is, at present, located near the subtropical front (STF), as it was during the Neogene, despite a 10∘ northward tectonic drift of Tasmania. We analysed glycerol dialkyl glycerol tetraethers (GDGTs – on 433 samples) and alkenones (on 163 samples) and reconstructed the paleotemperature evolution using TEX86 and U37k′ as two independent quantitative proxies. Both proxies indicate that Site 1168 experienced a temperate ∼ 25 ∘C during the early Miocene (23–17 Ma), reaching ∼ 29 ∘C during the mid-Miocene climatic optimum. The stepwise ∼ 10 ∘C cooling (20–10 ∘C) in the mid-to-late Miocene (12.5–5.0 Ma) is larger than that observed in records from lower and higher latitudes. From the Pliocene to modern (5.3–0 Ma), STF SST first plateaus at ∼ 15 ∘C (3 Ma), then decreases to ∼ 6 ∘C (1.3 Ma), and eventually increases to the modern levels around ∼ 16 ∘C (0 Ma), with a higher variability of 5∘ compared to the Miocene. Our results imply that the latitudinal temperature gradient between the Pacific Equator and the STF during late Miocene cooling increased from 4 to 14 ∘C. Meanwhile, the SST gradient between the STF and the Antarctic margin decreased due to amplified STF cooling compared to the Antarctic margin. This implies a narrowing SST gradient in the Neogene, with contraction of warm SSTs and northward expansion of subpolar conditions.

Spatio‐temporal patterns of ichthyoplankton in southern Chilean Patagonia: β‐diversity and associated environmental factors

AbstractFjords play an important role in biological productivity worldwide but are vulnerable to climate/anthropogenic effects. Chilean Patagonia (41°S–55°S) is one of the largest fjord ecosystems in the world, characterized by a complex geography with highly heterogeneous hydrographic conditions and a permanent input from oceanic water mass, both of which influence the ichthyoplankton distributional patterns. In this study, we analysed the distributional patterns of ichthyoplankton and its diversity during austral spring from 1996, 2009 and 2019 in the southern Chilean fjords (47°S–54°S). The area shows important latitudinal gradients of sea surface temperature (from 15°C to 5°C), fjord‐ocean variability in salinity (from 23 to 33) and water column temperature (3°C to 9°C). Spatial (but not temporal) variations in the composition and abundance of ichthyoplankton were recorded, caused mainly by differences in the abundance of larval Sprattus fuegensis, Maurolicus australis and Sebastes oculatus. Richness was higher on continental shelf and the lowest nearby fjord's head and ice fields. At the spatial scale, β‐diversity showed an increased species replacement (turnover) across areas, suggesting an important role of environmental conditions (e.g., salinity and water stratification) on the larval fish structure in this region. Ordination analysis indicates that changes in salinity and temperature, caused by ice melting, is the main environmental factor influencing the abundance of larval Thysanopsetta naresi (1996), Cataetyx messieri (2009) and Bathylagichthys parini (2019). Finally, this study highlights the importance of the conservation and protection of the Chilean Patagonia and monitoring ichthyoplankton communities, which are vital biomarkers of ecosystem health.

Биомная дифференциация российской Арктики

The article discusses various aspects of the biome division of the Russian Arctic and its significance for assessing climatic and anthropogenic changes in ecosystems. Different authors base the biome differentiation of the Arctic on the zonal-provincial principle, which takes into account the latitudinal temperature gradient and the meridional gradient of the continentality of the climate. As a result, from 6 to 20 or more biomes are allocated directly for the Russian Arctic to assess conveniently biodiversity, the response of ecosystems to climate change, to form a representative network of protected natural areas, etc. To characterize the climate and biodiversity, the authors use the schemes of biome division of the Russian Arctic, presented on the existing versions of maps of Russian biomes [10; 18]. They give quantitative characteristics of biomes that are important in relation to the regulation of economic activity and optimization of the territorial protection of biota and ecosystems in the Arctic.

How does lake primary production scale with lake size?

Kleiber’s 3/4-scaling law for metabolism with mass is one of the most striking regularities in biological sciences. Kleiber’s law has been shown to apply not only to individual organisms but also to communities and even the whole-ecosystem properties such as the productivity of estuaries. Might Kleiber’s law also then apply to lake ecosystems? Here, we show that for a collection of whole-lake primary production measurements, production scales to the 3/4 power of lake volume, consistent with Kleiber’s law. However, this relationship is not explicable by analogy to theories developed for individual organisms. Instead, we argue that dimensional analysis offers a simple explanation. After accounting for latitudinal gradients in temperature and insolation, whole-lake primary production scales isometrically with lake area. Because Earth’s topography is self-affine, meaning there are global-scale differences between vertical and horizontal scaling of topography, lake volume scales super-linearly with lake surface area. 3/4 scaling for primary production by volume then results from these other two scaling relationships. The identified relationship between the primary production and temperature- and insolation-adjusted area may be useful for constraining lakes’ global annual productivity and photosynthetic efficiency. More generally, this suggests that there are multiple paths to realizing the 3/4 scaling of metabolism rather than a single unifying law, at least when comparing across levels of biological organization.

Origination of the modern-style diversity gradient 15 million years ago.

The latitudinal diversity gradient (LDG) is a prevalent feature of modern ecosystems across diverse clades1-4. Recognized for well over a century, the causal mechanisms for LDGs remain disputed, in part because numerous putative drivers simultaneously covary with latitude1,3,5. The past provides the opportunity to disentangle LDG mechanisms because the relationships among biodiversity, latitude and possible causal factors have varied over time6-9. Here we quantify the emergence of the LDG in planktonic foraminifera at high spatiotemporal resolution over the past 40 million years, finding that a modern-style gradient arose only 15 million years ago. Spatial and temporal models suggest that LDGs for planktonic foraminifera may be controlled by the physical structure of the water column. Steepening of the latitudinal temperature gradient over 15 million years ago, associated with anincreased vertical temperature gradient at low latitudes, may have enhanced niche partitioning and provided more opportunities for speciation at low latitudes. Supporting this hypothesis, we find that higher rates of low-latitude speciation steepened the diversity gradient, consistent with spatiotemporal patterns of depth partitioning by planktonic foraminifera. Extirpation of species from high latitudes also strengthened the LDG, but this effect tended to be weaker than speciation. Our results provide a step change in understanding the evolution of marine LDGs over long timescales.

Globally invariant metabolism but density-diversity mismatch in springtails

Soil life supports the functioning and biodiversity of terrestrial ecosystems. Springtails (Collembola) are among the most abundant soil arthropods regulating soil fertility and flow of energy through above- and belowground food webs. However, the global distribution of springtail diversity and density, and how these relate to energy fluxes remains unknown. Here, using a global dataset representing 2470 sites, we estimate the total soil springtail biomass at 27.5 megatons carbon, which is threefold higher than wild terrestrial vertebrates, and record peak densities up to 2 million individuals per square meter in the tundra. Despite a 20-fold biomass difference between the tundra and the tropics, springtail energy use (community metabolism) remains similar across the latitudinal gradient, owing to the changes in temperature with latitude. Neither springtail density nor community metabolism is predicted by local species richness, which is high in the tropics, but comparably high in some temperate forests and even tundra. Changes in springtail activity may emerge from latitudinal gradients in temperature, predation and resource limitation in soil communities. Contrasting relationships of biomass, diversity and activity of springtail communities with temperature suggest that climate warming will alter fundamental soil biodiversity metrics in different directions, potentially restructuring terrestrial food webs and affecting soil functioning.

Sea surface temperature evolution of the North Atlantic Ocean across the Eocene–Oligocene transition

Abstract. A major step in the long-term Cenozoic evolution toward a glacially driven climate occurred at the Eocene–Oligocene transition (EOT), ∼34.44 to 33.65 million years ago (Ma). Evidence for high-latitude cooling and increased latitudinal temperature gradients across the EOT has been found in a range of marine and terrestrial environments. However, the timing and magnitude of temperature change in the North Atlantic remains highly unconstrained. Here, we use two independent organic geochemical palaeothermometers to reconstruct sea surface temperatures (SSTs) from the southern Labrador Sea (Ocean Drilling Program – ODP Site 647) across the EOT. The new SST records, now the most detailed for the North Atlantic through the 1 Myr leading up to the EOT onset, reveal a distinctive cooling step of ∼3 ∘C (from 27 to 24 ∘C), between 34.9 and 34.3 Ma, which is ∼500 kyr prior to Antarctic glaciation. This cooling step, when compared visually to other SST records, is asynchronous across Atlantic sites, signifying considerable spatiotemporal variability in regional SST evolution. However, overall, it fits within a phase of general SST cooling recorded across sites in the North Atlantic in the 5 Myr bracketing the EOT. Such cooling might be unexpected in light of proxy and modelling studies suggesting the start-up of the Atlantic Meridional Overturning Circulation (AMOC) before the EOT, which should warm the North Atlantic. Results of an EOT modelling study (GFDL CM2.1) help reconcile this, finding that a reduction in atmospheric CO2 from 800 to 400 ppm may be enough to counter the warming from an AMOC start-up, here simulated through Arctic–Atlantic gateway closure. While the model simulations applied here are not yet in full equilibrium, and the experiments are idealised, the results, together with the proxy data, highlight the heterogeneity of basin-scale surface ocean responses to the EOT thermohaline changes, with sharp temperature contrasts expected across the northern North Atlantic as positions of the subtropical and subpolar gyre systems shift. Suggested future work includes increasing spatial coverage and resolution of regional SST proxy records across the North Atlantic to identify likely thermohaline fingerprints of the EOT AMOC start-up, as well as critical analysis of the causes of inter-model responses to help better understand the driving mechanisms.