The Influence of Arctic Amplification on Mid-latitude Summer Circulation

Accelerated warming in the Arctic, as compared to the rest of the globe, might have profound impacts on mid-latitude weather. Most studies analyzing Arctic links to mid-latitude weather focused on winter, yet recent summers have seen strong reductions in sea-ice extent and snow cover, a weakened equator-to-pole thermal gradient and associated weakening of the mid-latitude circulation. We review the scientific evidence behind three leading hypotheses on the influence of Arctic changes on mid-latitude summer weather: Weakened storm tracks, shifted jet streams, and amplified quasi-stationary waves. We show that interactions between Arctic teleconnections and other remote and regional feedback processes could lead to more persistent hot-dry extremes in the mid-latitudes. The exact nature of these non-linear interactions is not well quantified but they provide potential high-impact risks for society

Tracking Iberian heatwaves from a new perspective

This paper presents a new heatwave (HW) detection algorithm that identifies spatially coherent HW patterns on synoptic scales and their temporal evolution, yielding the main characteristics (extension, intensity or persistence) of HW events (HWEs). The algorithm has been applied to temperature data from the ERA-Interim reanalysis in order to derive a catalogue of Iberian HWEs for the extended summers (June to September) of the 1979–2017 period. The results indicate mean frequencies of five Iberian HWEs and 16 summer days with HW conditions over Iberia (Iberian HWDs), with significant positive trends in both diagnostics. The analysis of the life-cycle reveals that more than half of the HWEs correspond to events that originated within the region. Although Iberian HWEs last more than one week on average, they tend to be transient, persisting for about three days in the region (Iberian phase), where they reach maximum intensity and extension, and evolving later to other areas. In order to identify recurrent patterns of occurrence, a clustering of Iberian HWEs was performed based on their mean temperature fields. Four clusters were obtained: Atlantic, Subtropical, European and Mediterranean events, which display distinctive characteristics and spatio-temporal evolution, causing HW conditions in western, southern, northern and eastern Iberia, respectively. Interestingly, Mediterranean events largely explain the overall trends in Iberian HWEs and HWDs. The connection between Iberian HWEs and atmospheric circulation patterns as summarized in four Weather Regimes (WRs) was also investigated. During the Iberian phase, HWEs are preferentially associated with ridge conditions in western Europe, with small variations in this WR determining different regional HWEs. However, the four types of regional Iberian HWEs tend to occur under different WRs during their pre- and post-Iberian phases, and show different relationships with WRs on seasonal scales. Using an impact-oriented metric for HWEs that accumulates the intensity of HW conditions over the areas affected by the event through its life-cycle, the top 10 Iberian HWEs were identified. They include well-known recent events such as those of August 2003, and June 2017. Flow analogues of the most outstanding Iberian HWEs reveal that recent warming has contributed to double their extension and intensity, making them more exceptional than they would have been in the past

Caracterización de la dinámica atmosférica mediante tipos de circulación y su relación con la variabilidad climática en la península ibérica

Tesis doctoral presentada en la Universidad De Murcia, Facultad de Biología.[ES]El clima a lo largo de toda su historia ha sufrido modificaciones importantes con un alto impacto en las sociedades y ecosistemas. Por ello, el estudio y análisis de las causas que provocaron dichos cambios presenta un gran interés, y más hoy en día, cuando las proyecciones de cambio climático, ligadas a una gran incertidumbre pero con una tendencia compartida en todos los estudios relacionados, nos informan de la posibilidad de cambios muy profundos en el clima a lo largo del presente siglo. No obstante, en el siglo pasado ya han empezado a producirse cambios significativos. Uno de los más destacados es el aumento de la temperatura media global del planeta, sobre el que los estudios de atribución señalan como principal culpable al aumento de las concentraciones en la atmósfera de Gases de Efecto Invernadero (GEI), provocado fundamentalmente por el mayor desarrollo de las actividades humanas desde principios de la revolución industrial. No obstante, tanto los cambios observados como las proyecciones de cambio climático reflejan comportamientos regionales diferenciados a lo largo del planeta. Así pues, algunos trabajos donde se emplearon simulaciones climáticas de épocas pasadas, han demostrado que el patrón espacial de calentamiento global que reflejan las proyecciones de cambio climático es el mismo en el que se proyectaron los cambios en el pasado, aunque con algunas diferencias regionales que podrían estar relacionadas con cambios en la circulación atmosférica inducidos por el forzamiento antrópico.[EN]Climate has suffered important changes along its history causing large impacts on society and ecosystems. Therefore, the analysis of the causes provoking such changes has a great interest, and much more nowadays, when climate change projections inform about the possibility of deep changes on climate along this century. Important climate changes have been occurred during the past century. One of the most significant is the global warming. Many studies point out to the human activities as the main responsible of such warming due to the huge anthropogenic Green House Gases (GHGs) emissions since the beginning of the industrial period. As the changes observed in the last decades as those projected for future, show regional behaviors overall the planet. Some works employing paleosimulations have demonstrated that the spatial warming pattern projected by the climate change simulations, is the same than that obtained for paleosimulations in the past, but with some regional differences maybe related to changes in the atmosphere circulation caused by anthropogenic forcing

Recent increases in winter snowfall provide resilience to very small glaciers in the Julian Alps, Europe

Very small glaciers (<0.5 km2) account for more than 80% of the total number of glaciers and more than 15% of the total glacier area in the European Alps. This study seeks to better understand the impact of extreme snowfall events on the resilience of very small glaciers and ice patches in the southeastern European Alps, an area with the highest mean annual precipitation in the entire Alpine chain. Mean annual precipitation here is up to 3300 mm water equivalent, and the winter snow accumulation is approximately 6.80 m at 1800 m asl averaged over the period 1979–2018. As a consequence, very small glaciers and ice/firn patches are still present in this area at rather low altitudes (1830–2340 m). We performed repeated geodetic mass balance measurements on 14 ice bodies during the period 2006–2018 and the results show an increase greater than 10% increase in ice volume over this period. This is in accordance with several extreme winter snow accumulations in the 2000s, promoting a positive mass balance in the following years. The long-term evolution of these very small glaciers and ice bodies matches well with changes in mean temperature of the ablation season linked to variability of Atlantic Multidecadal Oscillation. Nevertheless, the recent behaviour of such residual ice masses in this area where orographic precipitation represents an important component of weather amplification is somehow different to most of the Alps. We analysed synoptic meteorological conditions leading to the exceptional snowy winters in the 2000s, which appear to be related to the influence and modification of atmospheric planetary waves and Arctic Amplification, with further positive feedbacks due to change in local sea surface temperature and its interactions with low level flows and the orography. Although further summer warming is expected in the next decades, we conclude that modification of storm tracks and more frequent occurrence of extreme snowfall events during winter are crucial in ensuring the resilience of small glacial remnants in maritime alpine sectors

The fingerprint of the summer 2018 drought in Europe on ground-based atmospheric CO2 measurements

During the summer of 2018, a widespread drought developed over Northern and Central Europe. The increase in temperature and the reduction of soil moisture have influenced carbon dioxide (CO2) exchange between the atmosphere and terrestrial ecosystems in various ways, such as a reduction of photosynthesis, changes in ecosystem respiration, or allowing more frequent fires. In this study, we characterize the resulting perturbation of the atmospheric CO2 seasonal cycles. 2018 has a good coverage of European regions affected by drought, allowing the investigation of how ecosystem flux anomalies impacted spatial CO2 gradients between stations. This density of stations is unprecedented compared to previous drought events in 2003 and 2015, particularly thanks to the deployment of the Integrated Carbon Observation System (ICOS) network of atmospheric greenhouse gas monitoring stations in recent years. Seasonal CO2 cycles from 48 European stations were available for 2017 and 2018.The UK sites were funded by the UK Department of Business, Energy and Industrial Strategy (formerly the Department of Energy and Climate Change) through contracts TRN1028/06/2015 and TRN1537/06/2018. The stations at the ClimaDat Network in Spain have received funding from the ‘la Caixa’ Foundation, under agreement 2010-002624

Summer weather becomes more persistent in a 2 °C world

Heat and rainfall extremes have intensified over the past few decades and this trend is projected to continue with future global warming1–3. A long persistence of extreme events often leads to societal impacts with warm-and-dry conditions severely affecting agriculture and consecutive days of heavy rainfall leading to flooding. Here we report systematic increases in the persistence of boreal summer weather in a multi-model analysis of a world 2 °C above pre-industrial compared to present-day climate. Averaged over the Northern Hemisphere mid-latitude land area, the probability of warm periods lasting longer than two weeks is projected to increase by 4% (2–6% full uncertainty range) after removing seasonal-mean warming. Compound dry–warm persistence increases at a similar magnitude on average but regionally up to 20% (11–42%) in eastern North America. The probability of at least seven consecutive days of strong precipitation increases by 26% (15–37%) for the mid-latitudes. We present evidence that weakening storm track activity contributes to the projected increase in warm and dry persistence. These changes in persistence are largely avoided when warming is limited to 1.5 °C. In conjunction with the projected intensification of heat and rainfall extremes, an increase in persistence can substantially worsen the effects of future weather extremes

Explaining Extreme Events of 2012 from a Climate Perspective

Attribution of extreme events is a challenging science and one that is currently undergoing considerable evolution. In this paper are 19 analyses by 18 different research groups, often using quite different methodologies, of 12 extreme events that occurred in 2012. In addition to investigating the causes of these extreme events, the multiple analyses of four of the events, the high temperatures in the United States, the record low levels of Arctic sea ice, and the heavy rain in northern Europe and eastern Australia, provide an opportunity to compare and contrast the strengths and weaknesses of the various methodologies. The differences also provide insights into the structural uncertainty of event attribution, that is, the uncertainty that arises directly from the differences in analysis methodology. In these cases, there was considerable agreement between the different assessments of the same event. However, different events had very different causes. Approximately half the analyses found some evidence that anthropogenically caused climate change was a contributing factor to the extreme event examined, though the effects of natural fluctuations of weather and climate on the evolution of many of the extreme events played key roles as well.Peer Reviewe

Letter from the soils I have designed with

In my practice and recently completed PhD, I have been investigating possible relationships between humans and their ecosystems that nurture the resilience of both, with a specific focus on plant communities. The methodology is a reflective process integrated within the practice of built and grown architectures. It defined an ecological practice as a secular form of architectural animism that conceives of places as beings with agency, that we garden with. Soils, although not in the foreground, were regularly mentioned for the definition of a site’s propensity through defining the levels of nutrients and water, and structural capacity... This paper reflects on a selection of the same case studies but this time from the point of view of soils. Soils are analysed as characters, persons, connecting the life and rhythms of humans, as well as other animals and plants, to geological and climatic temporalities. Of particular interest is how we can transfer to the future the varied forms of heritage embedded in the rituals of soil care, the biological (genetic), the ecological, the cultural. Simultaneously, the lens of “new materialism” is applied on this practice. The fields previously connected in the research were other architectural and art practices, ecology, landscape conservation, systems theory, as well as Taoist and Zen philosophies. The form of this reflection will grow into a weave of multiple letters, within which artefacts are embedded. It is conceived as much as a work of art as an academic piece of writing

Warming of the Willamette River, 1850–Present: The Effects of Climate Change and Direct Human Interventions

Using archival research methods, we found and combined data from multiple sources to produce a unique, 140 year record of daily water temperature (Tw) in the lower Willamette River, Oregon (1881–1890, 1941–present). Additional daily weather and river flow records from the 1850s onwards are used to develop and validate a statistical regression model of Tw for 1850–2020. The model simulates the time-lagged response of Tw to air temperature and river flow, and is calibrated for three distinct time periods: the late 19th, mid 20th, and early 21st centuries. Results show that Tw has trended upwards at ~1.1 °C /century since the mid-19th century, with the largest shift in January/February (1.3 °C /century) and the smallest in May/June (~ 0.8 °C /century). The duration that the river exceeds the ecologically important threshold of 20 °C has increased by ~20 days since the 1800s, to ~60 d yr-1. Moreover, cold water days below 2 °C have virtually disappeared, and the river no longer freezes. Since ~1900, changes are primarily correlated with increases in air temperature (Tw increase of 0.81 ±0.25 °C) but also occur due to increased reservoir capacity, altered land use and river morphology, and other anthropogenic changes (0.34 ±0.12 °C). Managed release of water influences Tw seasonally, with an average reduction of 0.27 °C and 0.56 °C estimated for August and September. System changes have decreased daily variability (σ) by 0.44 °C, increased thermal memory, and reduced interannual variability. These system changes fundamentally alter the response of Tw to climate change, posing additional stressors on fauna