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Latitude, longitude, and direction
Explains the concepts of latitude and longitude as well as the purpose of the compass rose on a map.
Book
Climate warming as a driver of tundra shrubline advance
1. Climate warming is predicted to alter ecological boundaries in high-latitude ecosystems including the elevational or latitudinal extent of tall shrubs in Arctic and alpine tundra. Over 60 studies from 128 locations around the tundra biome have investigated shrub expansion in tundra ecosystems; however, only six studies test whether shrublines are actually advancing up hill-slopes or northward into tundra where tall shrubs are currently absent. 2. We test the hypothesis that willow shrublines have expanded to higher elevations in relation to climate across a 50 × 50 km area in the Kluane Region of the southwest Yukon Territory, Canada by surveying of 379 shrubs at 14 sites and sampling of 297 of the surveyed shrubs at 10 sites. We compared growth and recruitment to climate variables to test the climate sensitivity of shrub increase using annual radial growth analysis, age distributions and repeat field surveys to estimate the current rate of shrubline advance. 3. We found consistent and increasing rates of recruitment of alpine willows, with estimates of faster advancing shrublines on shallower hill-slopes. Mortality was extremely low across the elevation gradient. Aspect, elevation and species identity did not explain variation in recruitment patterns, suggesting a regional factor, such as climate, as the driver of the observed shrubline advance. 4. Annual radial growth of willows was best explained by variation in summer temperatures, and recruitment pulses by winter temperatures. Measured recruitment rates are ~20 ± 5 individuals per hectare per decade (M ± SE) and measured rates of increased shrub cover of ~5 ± 1% per decade (M ± SE) measured at the Pika Camp site between field surveys in 2009 and 2013. Our results suggest that shrubline will continue to advance over the next 50 years, if growing conditions remain suitable. However, if future conditions differ between summer and winter seasons, this could lead to contrasting trajectories for recruitment vs. growth, and influence the vegetation change observed on the landscape. 5. Synthesis. Our findings in the context of a review of the existing literature indicate that elevational and latitudinal shrublines, like treelines, are advancing in response to climate warming; however, the trajectories of change will depend on the climate drivers controlling recruitment vs. growth.
Journal Article
Earth's hemispheres
The division of the Earth into hemispheres isn t the easiest concept to teach or grasp. It involves geography, spatial awareness, map-reading abilities, and more. This volume makes it easy for any reader to develop a solid comprehension of this critical social studies lesson! Vivid, full-color maps and photographs are integrated with accessible main text to aid young readers understanding of this sometimes-tough topic. This essential book is a useful and valuable addition to any library s collection!
Book
Genetic diversity within populations of an arctic–alpine species declines with decreasing latitude across the Northern Hemisphere
Aim: We identified and evaluated general latitudinal trends in genetic diversity within populations of a widespread arctic–alpine plant, Dryas octopetala, to examine the applicability to this species of the dominant hypothesis that intraspecific genetic diversity is highest in the tropics and declines towards the poles. Location: The circumpolar Arctic and northern temperate alpine ranges, with a focus on high altitude mountains at the species lowest latitudinal margin in the Japanese archipelago. Methods: Within-population genetic diversity was assessed using genotypes determined at nine microsatellite loci (n = 489), chloroplast DNA sequences (atpB-rbcL and trnV-ndhC spacers, n = 181) and a nuclear gene sequence (LEAFY, n = 173) of 18 populations, as well as a previously published amplified fragment length polymorphism data-set for 26 populations, across the distributional range of the species. The latitudinal pattern of intra-population genetic diversity was modelled at hemispheric scale to discriminate linear latitudinal and quadratic central-marginal trends in genetic diversity. Population genetic structure was assessed by Bayesian clustering analyses. Results: At hemispheric scale, we identified two interacting effects: a general latitudinal decline in genetic diversity towards the equator and a central–marginal effect, whereby genetic diversity decreases towards the margins of a species' range. This decrease was more marked in low-latitude marginal populations than in high-latitude marginal populations. Populations at the lowest latitudes in the Japanese archipelago showed the lowest level of genetic diversity but exhibited distinctive genetic variation. Main conclusion: The latitudinal decline in genetic diversity within populations of this arctic–alpine plant across its range was opposite to the commonly observed trend. A significant part of the equator-ward latitudinal decline in genetic diversity in this arctic–alpine species may be attributable to a \"sky island\" effect, which played a greater role at low latitudes.
Journal Article
Oceanic Feedback to the Atmosphere for Anomalous SST Events Peaking in Early Winter in the Northeast Pacific
In the past decade, large‐scale and persistent warm sea surface temperature anomalies (SSTA) occurred frequently in the mid‐latitude Northeast Pacific (NEP), offering a valuable opportunity to further illuminate the oceanic feedback to the atmosphere, which has been a complex issue for mid‐latitude ocean‐atmosphere interaction. Previous studies reported that the prolonged warm SSTAs in the NEP are usually passively triggered by atmospheric high‐pressure anomalies. In this study, results show that the early winter positive SSTAs can actively reverse the high‐pressure anomalies into low‐pressure anomalies within the whole troposphere through diabatic heating and transient eddy vorticity forcing. However, when the positive SSTAs appear in mid‐winter, the atmospheric preconditioning of warm air temperature anomalies related to the high‐pressure anomalies prevents oceanic thermodynamic and dynamics feedback onto the atmosphere, which results in no reversal of the high‐pressure anomalies. Therefore, the atmospheric state is an important factor in initiating the mid‐latitude oceanic feedback to the atmosphere.
Journal Article
High‐Latitude Joule Heating in TIE‐GCM 3.0: Evaluation of Different Plasma Convection Forcing Models
We systematically evaluate the high‐latitude Joule heating of the recently released version 3.0 Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE‐GCM) by comparison to EISCAT incoherent scatter radar measurements. The model performance is examined using normalized root mean square deviations derived from test runs driven by different convection patterns from empirical and data‐assimilated models. The following features are revealed: (a) Data‐assimilated geomagnetic forcing improves the agreement between modeled and EISCAT‐derived Joule heating rates by 8%, 28%, and 54% for low, moderate, and high geomagnetic activity. (b) Increasing model grid resolution from 2.5° to 1.25° leads to ∼ ${\\sim} $20% higher Joule heating rates. (c) AMIE‐driven runs better reproduce the magnitude of the Joule heating rates, AMGeO‐driven runs the vertical profile. (d) Internal model time step resolution has no effect on the Joule heating rates.
Journal Article
Compound Dry–Hot Conditions in South and Southeast Asia Modulated by the Arctic Stratospheric Polar Vortex
Compound dry–hot conditions increasingly threaten South and Southeast Asia, highlighting the need to understand drivers. Observations and numerical simulations reveal a robust polar–low‐latitude teleconnection: the March Arctic stratospheric polar vortex (ASPV) strongly modulates March–April compound dry–hot conditions across the region. When the March ASPV weakens, anomalous easterlies in the lower Arctic stratosphere induce corresponding tropospheric easterlies and persist through April, cooling Siberia and accelerating the mid‐latitude westerlies. The resulting anticyclonic shear drives an anomalous anticyclone over northern South and Southeast Asia. Combined with the region's climatologically dry–hot season, these processes promote compound dry–hot conditions further amplified by positive soil moisture–atmosphere feedback. Moreover, the March ASPV outweighs the preceding winter tropical sea surface temperature in shaping compound dry–hot variability in this northern sector. Our results highlight the critical role of the Arctic stratospheric anomalies in driving low‐latitude climate, helping improve risk mitigation.
Journal Article
The Mother's Day Geomagnetic Storm on 10 May 2024: Aurora Observations and Low Latitude Space Weather Effects in Mexico
On 10 May 2024, a severe geomagnetic storm coinciding with Mother's Day in Mexico lasted over 40 hr and produced polar auroras observable at low latitudes. This storm, the most intense since 2003, resulted from a series of solar flares and coronal mass ejections from active region 3664. The event was significant for space weather studies in Mexico, marking a milestone by enabling comprehensive measurements of its effects. The Mexico Space Weather Service (SCIESMEX) and the National Space Weather Laboratory (LANCE) had prepared for such an event since their inception. LANCE's instrument networks recorded solar chromospheric images, solar radio bursts, geomagnetic variations, Schumann resonances, ionospheric disturbances, and energetic particle flows. They also monitored Geomagnetically Induced Currents (GICs) in three strategic substations of the national electrical system. This provided unprecedented insights into the dynamics of severe space weather events at the North‐American low‐latitude environment. Citizen science efforts documented auroras and regional responses, capturing variations in geomagnetic indices, ionospheric disturbances, cosmic ray fluxes, GICs, and technological impacts. SCIESMEX worked with the National Civil Protection System (SINAPROC) to issue warnings, ensuring public awareness and preparedness. This coordination underscores the importance of effective communication and collaboration in mitigating impacts. The May 2024 geomagnetic storm demonstrated the critical role of preparedness, research, and public education in reducing the effects of future space weather events in Mexico.
Journal Article
How Has the Ferrel Cell Contributed to the Maintenance of Antarctic Sea Ice at Low Levels From 2016 to 2022?
This study investigates the specific circulation anomalies that have sustained the low Antarctic sea ice state since 2016. Firstly, we find a significant strengthening and southward shift in the Ferrel Cell (FC) during 2016–2022, resulting in a marked increase in southward transport of heat and moisture. Secondly, this enhanced FC is closely associated with a stronger mid‐latitude wave pattern. This pattern is zonally asymmetric and greatly amplifies the poleward advections of heat and moisture, leading to the increased downward longwave radiation, more liquid precipitation and sea ice retreat in specific regions, including the western Pacific and Indian Ocean sectors, Ross and northern Weddell Seas. The mechanism deduced from the short‐term period is further supported by the results of 40 ensemble members of simulations. The southward expansion of the FC and sea ice decline are closely linked to La Niña‐like conditions but may also be driven by anthropogenic global warming. Plain Language Summary Following the sudden decline in 2016, the Antarctic sea ice extent has persisted at historically low levels. In 2023, it reached unprecedented record lows. However, the specific atmospheric circulation anomalies that have sustained the Antarctic sea ice at low levels are still unknown. It is well‐established that the Ferrel Cell, a mid‐latitude atmospheric meridional circulation, plays a pivotal role in the energy exchange between the high‐ and mid‐latitudes. Our findings indicate that the enhanced Ferrel Cell zonally intensified southward transport of heat and moisture over the sea ice regions, which sustains the overall low Antarctic sea ice state. Additionally, in the horizontal plane, the enhanced mid‐latitude wave pattern is responsible for the regional sea ice retreat over the western Pacific sector, Ross Sea, Indian Ocean sector, and northern Weddell Sea, and is also closely associated with the enhanced Ferrel Cell. The effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations. Therefore, this study suggests that concurrent with the southward shifting of the Ferrel Cell, the stronger warm and moist air intrusions, and the increased liquid precipitation, restrict the Antarctic sea ice expansion following its sudden decline. Key Points Since 2016, the low Antarctic sea ice extent has persisted, consistent with heat and moisture accumulation over the sea ice edges The Ferrel Cell was enhanced and shifted southward, leading to the increased southward heat/moisture advection, and liquid precipitation The effects of the enhanced Ferrel Cell on Antarctic sea ice decline are further supported by the results of large ensemble simulations
Journal Article
The Future of Midlatitude Cyclones
Purpose of Review
This review brings together recent research on the structure, characteristics, dynamics, and impacts of extratropical cyclones in the future. It draws on research using idealized models and complex climate simulations, to evaluate what is known and unknown about these future changes.
Recent Findings
There are interacting processes that contribute to the uncertainties in future extratropical cyclone changes, e.g., changes in the horizontal and vertical structure of the atmosphere and increasing moisture content due to rising temperatures.
Summary
While precipitation intensity will most likely increase, along with associated increased latent heating, it is unclear to what extent and for which particular climate conditions this will feedback to increase the intensity of the cyclones. Future research could focus on bridging the gap between idealized models and complex climate models, as well as better understanding of the regional impacts of future changes in extratropical cyclones.
Journal Article