Atmospheric science concerns itself with investigating the physical, chemical and radiative properties of the Earth’s atmosphere. Polar atmospheric science received a great deal of attention in the late 20th century with the 1985 discovery of the Antarctic “Ozone Hole”; a discovery that led to the Montreal Protocol and a comprehensive global ban of chlorofluorocarbons. While the monitoring of CFC’s and studies of polar stratospheric clouds continues, polar atmospheric science has received renewed attention during the IPY because of its important role in global climate.
The atmosphere over Antarctica serves as a laboratory for investigating the remote background atmosphere. Since it is far from anthropogenic pollution sources, short-lived species (e.g. aerosols, VOC’s) are nearly absent. However, the presence of long-lived trace gases (e.g. CO2) is used to study the rate of global redistribution of man-made pollution. We find that the Arctic atmosphere is much different than its antipode. Each spring the Arctic atmosphere is affected by “Arctic Haze”. This winter/spring reduction in visibility within the polar vortex has been observed since at least the 1950’s and is directly attributed to anthropogenic air pollution in the Northern Hemisphere.
The buildup of atmospheric pollution in the Arctic is of particular concern for two reasons. First, atmospheric aerosols scatter and absorb incoming/outgoing solar radiation directly affecting the radiation budget of the Arctic environment. Anthropogenic aerosols typically contain light-absorbing black carbon which can lead to direct heating of the Arctic atmosphere; heating which is in addition to the gradual rise of global temperature due to GHG’s. Second, aerosols serve as cloud and ice condensation nuclei making them a key component of the hydrological cycle. The light-absorbing properties of the aerosol continue once they are deposited with precipitation. This reduction in snow/ice albedo potentially affects the terrestrial hydrological cycle of the Arctic by accelerating the melting of permanent snow and ice. The composition of meltwaters is also affected since trace-gases and aerosols can deposit inorganic salts (e.g. H2SO4, HNO3, NH4+), trace metals (e.g Hg0, Cd), and volatile organic compounds (e.g. benzene, MTBE) which are not ordinarily found in the Polar Regions.
As we so often find in Polar Science, the study of the polar atmospheres is more difficult than at mid-latitudes. Satellites retrievals over the poles are complicated by bright surface targets (i.e. snow, ice) as well as seasonal or persistent cloud cover. Also, there is a dearth of surface-based and vertical column measurements with which to constrain global climate models. Many of these and other issues related to Polar Atmospheric Science were investigated during IPY. And in the years to come, answers to some questions may be found within the IPY data. However, the sparse nature of the observations, their short duration, and the rapidly changing environment of the Polar Regions will ensure that study of the Earth’s Polar Atmospheres will continue for years to come.
What is the difference between Climate and a Climate System?
Climate - The long-term average of conditions in the atmosphere, ocean, and ice sheets and sea ice described by statistics, such as means and extremes.
Climate System - The matter, energy, and processes involved in interactions among Earth’s atmosphere, hydrosphere, cryosphere, lithosphere, biosphere, and Earth-Sun interactions.
What is the difference between Climate Change and Global Warming?
Climate Change - A significant and persistent change in the mean state of the climate or its variability. Climate change occurs in response to changes in some aspect of Earth’s environment: these include regular changes in Earth’s orbit about the sun, re-arrangement of continents through plate tectonic motions, or anthropogenic modification of the atmosphere.
Global Warming - The observed increase in average temperature near the Earth’s surface and in the lowest layer of the atmosphere. In common usage, “global warming” often refers to the warming that has occurred as a result of increased emissions of greenhouse gases from human activities. Global warming is a type of climate change; it can also lead to other changes in climate conditions, such as changes in precipitation patterns.
CLIMATE LITERACY: The Essential Principles of Climate Science
- The Sun is the primary source of energy for Earth’s climate.
- Climate is regulated by complex interactions among components of the Earth system.
- Life on Earth depends on, is shaped by, and affects climate.
- Climate varies over space and time through both natural and man -made processes.
- Our understanding of the climate system is improved through observations, theoretical studies, and modeling.
- Human activities are impacting the system.
- Climate change will have consequences for the Earth system and human lives.
Polar and Alpine Research Areas
The number of research topics covered by Polar and Alpine research is vast and our members are involved in both natural and social sciences disciplines. The aim of this page is to provide someone new to the topic an overview of research areas involved in Polar and Alpine research and provide a snapshot of some disciplines that are being researched by APECS members.
Glaciology is the study of glaciers, from small alpine valley glaciers with complex hydrology and influence over the local environment to large ice sheets with significant importance to global climate and sea-level. The majority of the world's glaciers are found in the polar regions and they have fundamental impacts on almost all areas of polar research. There are strong interdisciplinary links in particular with geology, hydrology, oceanography and atmospheric sciences.
There are a number of sub-disciplines or areas of research within Glaciology, often linking into other disciplines such as earth-sciences and physics. Here are a few; click on them to learn more about these exciting areas of study.
Glacial geomorphology involves the study of glacial landforms. It is important to understand how glaciers have behaved in the past in order to predict what will occur in the future. Glacial geomorphologists combine a knowledge of glacial processes with observation of landforms to infer glacier behaviour over the last decades to millions of years.
Remote sensing is an important technique for observing present day glacier change. Satellite remote sensing has developed rapidly over recent years with the launch of satellites such as ICESat and Cryosat designed specifically for monitoring polar ice. These satellites are complemented by airborne and ground-based remote sensing techniques. Changes in the mass of polar ice sheets can now be measured using satellites such as GRACE to record small variations in the earth's gravity; changes in ice volume are measured by high precisions altimeters and changes in the mass budget of the ice sheets are measured by feature tracking and interferometric synthetic aperture radar (InSAR).
Glacier modelling is used to predict the future of ice sheets and glaciers. Developing useful glacier models is vital in predicted the influence of changing climate on global sea-level and water resources. Ice sheet and glacier models vary in scale from high resolution simulations of iceberg calving and ice shelf fracture mechanisms to full approximations of ice sheet response to climate over thousands of years.
Ice Core Studies:
Permafrost is recognized by the World Climate Research Programme (WCRP/WMO) and Climate and Cryosphere (CliC) as a key element of the Earth System. Permafrost is present in ca. 25% of the Northern Hemisphere continental area and on all the ice-free areas of the Antarctic continent, including wide areas under the ice-sheet. Permafrost is central to the carbon cycle and hence to the climate system, especially due to methane and carbon dioxide release following permafrost degradation. This issue is especially sensitive in the Arctic, but detailed studies are lacking in the Antarctic. Therefore, especially in the ice-free areas, the warming of permafrost (climatic and human-induced) can generate problems to existing or planned research facilities, which can be potentially subject to risk. Permafrost monitoring is therefore also an important issue relating to environmental impact assessment and mitigation in ice-free terrain Antarctic facilities.
Sea ice is defined as ice that grows in the ocean. It is an integral component in an intricate ecosystem that provides stability and nourishment in the food web in the Arctic and Antarctic regions. Though this is a significant component in ecological, biogeochemical, and geophysical systems at the poles, it also influences oceanic and atmosphere interaction on a global level. The physical structure of sea ice provides a significant contribution to Earth's ability to reflect and absorb incoming solar radiation. The reflectivity studied is known as albedo, which is the ratio of outgoing reflected radiation from the surface to incoming radiation. Optical properties in the different sea ice types, such as brine inclusions, air, and solid salts, govern the portion of incoming radiation that is reflected,absorbed, and scattered. Another important aspect of sea ice thickness pertains to the sea ice brine flux and its effect on thermohaline circulation (THC) affecting deepwater formation and upper ocean stability through saltwater and freshwater fluxes.
Within the past few decades, global climate change has led to widespread changes in the mass and aerial extent of the Earth's glaciers, ice sheets, and sea ice as well as changes in the temperature and circulation of the oceans. This research feature focuses on the interactions between glaciers, ice sheets, sea ice and the oceans, the feedbacks inherent to the coupled systems, and the broader impacts of changes in ice-ocean interactions. The following two sections provide a brief overview of ice-ocean interactions at/near glacier margins and beneath sea ice.
Glacier ice-ocean interactions: Glaciers that terminate in the ocean (i.e., marine-terminating or tidewater glaciers) lose mass at their marine margins through iceberg calving, meltwater runoff and submarine melting. The stability of a glacier is dependent on a balance between mass entering and exiting a catchment. In contrast with land-terminating glaciers, marine-terminating glaciers are able to undergo rapid changes in mass because changes in ocean forcing can lead to rapid changes in the calving and/or submarine melt rates, which can influence glacier flow dynamics by controlling the location and shape of the glacier terminus (which can be grounded or floating). The location and shape of the terminus influences the balance of stresses controlling ice flow; thus, changes in ice-ocean interactions have the potential to strongly influence a glacier’s mass balance.
The magnitude and timing of iceberg calving can be quantified using remote sensing and in situ observations (e.g., satellite imagery, time lapse photography, scanning lidar, and seismic measurements), however the processes controlling calving are poorly understood. Observations and modeling suggest that calving is a two-stage process: (1) fracture/detachment and (2) seaward transport. Transport of the detached ice can be influenced by both the thickness of the glacier relative to the depth of the neighboring ocean and the rigidity of ice mélange (a mixture of sea ice and icebergs).
Due to the difficulty in predicting the magnitude and timing of calving events, the proglacial environment of a tidewater glacier is not easily accessible and direct measurements of submarine melting and subglacial runoff are difficult to collect. Numerical and physical models used to look at this relationship have found that the enhancement of submarine melting occurs when cold fresh buoyant meltwater from the subglacial system entrains warm saline ocean water as it moves up the glacier terminus towards the ocean surface. As such, the magnitude of submarine melting will vary with both the ocean water temperature and the strength of the rising subglacial meltwater plume. Estimated melt rates suggest that submarine melting can be on the order of meters per day for some glaciers but vary widely between glaciers. It has also been suggested that an increase in submarine melt rates in the 1990s and 2000s may have triggered the recent rapid changes in ice flow at numerous outlet glaciers draining the Greenland and West Antarctic ice sheets. However, the construction of submarine melt rate time series is hindered by the scarcity of in situ hydrographic observations and the limitations of remote sensing techniques, preventing a thorough analysis of temporal changes in submarine melting with respect to changes in glacier behavior.
Tidewater glacier stability and the impact of tidewater glaciers on their environment is complex due to the numerous feedbacks occurring in the glacier ice-ocean system. The impact of changes in the glacier-ocean system is not only limited to sea level rise, but also smaller scale changes such as local biologic communities that rely on calved icebergs for breeding or nutrient-rich meltwater plumes for food. Thus, it is imperative that research efforts continue to focus on developing a better understanding of glacier ice-ocean interactions.
Sea Ice-ocean interactions: Sea ice is a key indicator of the global climate change. Recent decades have been marked by rapid sea ice decline in the Arctic Ocean. In contrast, no significant decrease in Southern Ocean sea ice has been observed. Although the widespread changes in sea ice are concurrent with changing atmospheric and oceanographic conditions, sea ice-climate models are generally not capable of properly simulating the observed variability of Arctic and Antarctic sea ice cover. The failure of these models is likely due to the poor understanding of processes governing sea ice-ocean interactions. As such, a better understanding of sea ice-ocean interactions and an improved parameterization in climate and sea ice in Earth system models must be developed.
An important aspect of sea ice-ocean interactions that warrants further exploration and model development is the interaction of sea ice and the ocean with the atmospheric boundary layer. The formation and melting of sea ice in the polar regions are critical processes that must be included in Earth system models because the associated heat, moisture, momentum and gas exchanges at the ocean-sea ice-atmosphere interface are strongly influenced by changes in sea ice cover. Additionally, changes in sea ice cover influence the penetration of solar radiation and wind-induced turbulent mixing of the upper ocean layer, which will influence the biogeochemical cycling and ecosystem functioning in the upper ocean layer and lower atmosphere.
It is important to remember that the current state of knowledge regarding sea ice-ocean interactions was developed over the past several decades; a time period marked by a shift from relatively stable sea ice cover to the most recent period of declining sea ice extent and thickness. As such, the recent changes in sea ice extent, thickness, and distribution (particularly in the Arctic Ocean) have revealed knowledge gaps that must be addressed by the scientific community in a timely manner. For example, the recent transition from widespread multi-year sea ice towards predominantly first-year ice in the Arctic may enable the penetration of a more solar radiation beneath the ice than observed in the past. Consequently, the upper-ocean warming associated with increased penetration of solar radiation can contribute to enhanced melting of sea ice, further enhancing absorption of solar radiation by the upper ocean layer (i.e., positive feedback loop). Changes in sea ice cover and associated changes in the upper ocean temperature and salinity can lead to changes in sea ice algae/phytoplankton productivity, which will in turn influence the marine food web and carbon cycling. Interconnections such as these make the study of sea ice-ocean interactions an inherently multidisciplinary task.
While polar terrestrial ecosystems appear to be snow and ice deserts most of the time, their marine counterparts bustle with life throughout the year. Vast amounts of plankton and ice-associated organisms sustain the marine, but also major parts of the terrestrial food web, all the way up to the highest predators, including penguins, seals and polar bears. Their annual cycles are extremely seasonal, but the strong plankton blooms in the spring set off a feeding extravaganza that does not only sustain the local fish, bird and sea mammal life, but even causes huge whales to travel to the polar regions over thousands of miles to feast there. Although the planktonic community is generally not very species-rich, its high abundance provides food input for an astonishing diverse and colourful benthic fauna as well. However, systems with low numbers of species are at the same time more vulnerable for impacts of global changes. International and interdisciplinary research efforts attempt to understand the biological responses to warming, sea ice retreat, freshwater input and other anthropogenic impacts such as ocean acidification and pollutants. Various types of models are developed to predict changes in the marine community structure that will impact greatly on these ecosystems and may have major repercussions on a global scale. These predictions can only be made in close collaboration with other disciplines such as physical oceanography and atmospheric sciences.
The ocean does not only cover two thirds of the Earth’s surface thereby linking polar regions and the tropics but it is also home to a multitude of microbial species, fish and mammals, it provides food for many people, and it buffers climate change.
Already now scientists observe rapid sea ice decrease and sea level rise endangering rare species like the polar bear but also entire human settlements in shallow coastal regions. What will happen to the CO2 storage capacity of the ocean with increasing water temperatures? And how will fish, penguins, albatross and seals survive if humans keep harvesting krill? All these questions, concerns, and much more is addressed in the various fields of research related to polar marine science.
Limnology is the study of inland waters ranging in size from large lakes down to puddles, as well as wetlands and running-water systems such as streams, rivers and estuaries. Inland waters range from very fresh glacier- or groundwater-fed systems, to brackish saline waters in isolated or ocean-influenced basins. Inland water bodies can be permanent features of the landscape, or may be ephemeral features that are only present seasonally. The wide variation in possible sizes, physicochemical characteristics and permanence of inland waters makes limnology a very diverse field of study!
Studying limnology in polar regions adds even more complexity – there are extreme variations in light, nutrient availability and temperature amongst seasons. The presence of a seasonal ice cover, near-desert conditions in surrounding tundra landscape, and very low temperatures all exert strong influences on polar inland waters.
Limnology is an important field of study in the polar regions because lakes and rivers are abundant in the arctic, and in some parts of Antarctica as well. Understanding the processes that occur within a catchment gives a better perspective on interactions within the landscape. For instance, biogeochemical processes generally occur more rapidly in water than they do in polar soils or terrestrial vegetation, making aquatic habitats hot spots for biodiversity and productive aquatic food webs. In the arctic, processes occurring in inland waters also have important impacts on the world’s oceans, because riverine outflow to the Arctic Ocean influences the global thermohaline circulation.
Microbial ecology is the study of interrelationships between microorganisms and the living and non-living aspects of the environments that they inhabit. Microorganisms are important players in Polar habitats, where they are major drivers of biogeochemical cycles in aquatic and terrestrial ecosystems. In the Arctic, for example, the thawing of permafrost could lead to increases in microbial activities and carbon decomposition, resulting in accelerated release of greenhouse gases. In the Antarctic, microorganisms are important in mediating nutrient cycling in surface lakes and subglacial environments, which are thought to carry important nutrients to the surrounding Southern Ocean. Additionally, studies focusing on the survival mechanisms of microbes exposed to sub-zero conditions or freeze-thaw cycles contribute to our understanding of the resilience of life and to advances in the fields of biotechnology and astrobiology. Answering basic questions about microbial ecosystems can be difficult, as the systems cannot be observed directly, but recent technological advances allow the construction of molecular “blueprints”, which are keys to describing and understanding microbial ecosystems. Large quantities of these molecular data help inform our understanding of microbial population structures and metabolic activities, as well as how these elements interact with the environment as a whole. Combining current molecular approaches with field-based measurement and laboratory-based culture studies allows today’s microbial ecologists to examine important issues ranging from the impact of changing climate on nutrient cycling to life’s ability to survive in extreme environments.
Anthropology is the scientific study of the origin and behavior of man, including the development of societies and cultures. Traditionally anthropology is divided into two fields, biological anthropology and cultural anthropology, both of which have their own sub-branches.
Biological anthropology focuses on the study of human populations using an evolutionary framework. Biological anthropologists have theorized about how the globe has become populated with humans, as well as tried to explain geographical human variation.
Cultural anthropology is the study of culture based on methodology that heavily relies on participant-observation. Cultural anthropologists use ethnographic examples to defend their theories. Ethnography is the product of research, a monograph or book describing in detail a specific culture. Indeed, the process of participant-observation can be especially helpful to understanding a culture from an emic point of view; which would otherwise be unattainable by simply reading from a book. The study of kinship and social organization is a central focus of cultural anthropology, as kinship is a human universal. Cultural anthropology also covers economic and political organization, law and conflict resolution, patterns of consumption and exchange, material culture, technology, infrastructure, gender relations, ethnicity, childrearing and socialization, religion, myth, symbols, values, etiquette, worldview, sports, music, art, nutrition, recreation, games, food, festivals, and language.
Because of the holistic nature of anthropological research, all branches of anthropology have widespread practical application in diverse fields. This is known as applied anthropology. Thus military expeditions employ anthropologists to discern strategic cultural footholds; marketing professionals employ anthropology to determine propitious placement of advertising; and humanitarian agencies depend on anthropological insights as means to fight poverty. Examples of applied anthropology are ubiquitous.
Antarctica encompasses a rich range of human interactions that is increasingly becoming inseparable from its natural environment. Although no indigenous populations live on Antarctica, the continent is home to scientific research stations from 30 different countries and is the destination of choice for an increasing number of tourists. Understanding the history of human presence, its social and anthropological dynamics, its politics and its shared cultural constructions are important themes in Antarctica Social Science research and management. The Antarctic Treaty was ratified in 1961 to ensure “in the interests of all humankind that Antarctica shall continue forever to be used exclusively for peaceful purposes and shall not become the scene or object of international discord”. However, as several countries have overlapping territorial claims, future geopolitical tensions could jeopardize the treaty. Millions of people have been exposed to Antarctica through its popularization in the media (books, film, TV, art) and this has prompted curiosity and questions of value. The costs of human presence in Antarctic are remarkable from economical, environmental and cultural points of view. Therefore, Antarctica has become the object of innumerable debates and balancing these different viewpoints could have global implications particularly when they affect climate and international policy. Thus, Antarctic Social Science provides a vital contribution to the region's future.
What do Antarctic Social Scientists research? Below you can find a list of the wide variety of topics researched by APECS members, together with a brief explanation of the topic. To find out more about experts in each field, visit the SCAR Humanities and Social Sciences web page at http://antarctica-ssag.org/ :
Anthropology: For Sociocultural Anthropology, Antarctica is an emerging scenario of practices and associations between humans and non-humans, spatially located and specifically built and experienced by men and women who live and work in Antarctica. From ethnographic work in Antarctica, anthropologists have established their everyday relationships in the field, with scientists and military personnel mainly, trying to understand in situ, how the practices and techniques of everyday life that human beings establish and run, give substance and senses to the associations and networks which build the exceptional values and uses of Antarctica and the Antarctic Treaty System. It is from the ethnographic study of this process by which Anthropology aims to understand the modes, powers and tensions of inter-trans-nationals that characterize the processes of human colonization of Antarctica. Antarctica is an exciting research field for anthropologists. Still, it was not explored enough by this discipline. Only five known anthropologists studied the Antarctic: Palinkas, O'Reilly, Resende de Assis, Soto and Salazar. But if anthropologists in the Antarctic are few, their work open the field of research, attracting readers and students. By using ethnography as a method they research settlements and Antarctic National Programs (USA, Brazil, New Zealand, Chile and Australia) they grow elemental data for the understanding of micro-societies, socio-environmental dwelling strategies, transnational networks and local movements to implement the Antarctic Treaty System. They also produce pioneer research over scientific, military and logistical practices in the ice, gender and labor relations, the emergence of gateway cities (e.g. Ushuaia and Christchurch) and arising symbolic and moral values connected to the Antarctic.
International Law: Exploration of Antarctica began in earnest when the classical era of Imperialism was beginning to come to a close, with the emergence of the two Cold War-era superpowers following suit. This led to the emergence of a singular legal regime superseding previously accepted notions such as effective occupation, with science at its core and an attempt to limit both geopolitical competition and environmental impact. The study of the 1959 Antarctic Treaty and the wider “Antarctic Treaty System” is of interest to legal scholars not only in and by themselves, but also to reflect on some of the possible directions international law may take in the future. In this regard, it may be of particular interest to those working on territorial disputes, natural resources law, and space law. At the same time, technological change, thirst for resources, continued competition and tensions among nations, and the (re)emergence of powers not associated with the birth of the regime, are putting added strains on the system. To sum it up, just like many fields in modern science have benefited from that giant laboratory called Antarctica, so can more than a few areas of the law. Stay tuned to learn more!
International Relations: Antarctica is by definition an international arena, given the combination of (sometimes overlapping) territorial claims, an international legal regime, and scientific activities by many countries. Cooperation and competition takes place hand by hand, and while the latter has taken a peaceful form in the continent herself, we cannot forget that the surrounding area has sometimes been home to armed conflict, as in the 1982 Falklands War. Antarctica is essential in terms of soft power for any country wishing to appear as a leading nation in the eyes of the world, while at the same time providing some hope to those voices wishing to leave behind territorial conflicts and zero-sum competition for resources in favor of greater understanding and cooperation. The region also shows how international civil society is coming to have a greater voice in global affairs, no longer the exclusive domain of the nation-state. For these, and many other reasons, no serious student of international affairs can afford to ignore Antarctica. Make sure to follow us!
Sociology: Environmental forces, animal life, or natural events are no longer the only ones that need to be taken into consideration for those who aim to understand Antarctica. Nowadays, social relations inside and outside Antarctica, produce effects on its wilderness that can no longer be ignored, as the region now encompasses a broad range of human relations and interactions that must be understood in order to comprehend and preserve its whole existence. Social interactions are held by visitors, tourists, researchers, policy makers, and all who build and share common perceptions about this place and their experience on it. Besides, host societies get informed about Antarctica, creating and reproducing different collective imaginaries by these reports. Consequently, they directly influence the region’s outcomes as well. Therefore, as Antarctic development is deeply intertwined with human interaction, social studies on Antarctic practices are vital for those who want to understand it as a whole.
Polar research involves knowledge gathering and information integration from many sources. In the Polar Regions, Traditional Knowledge (TK) plays a central and important role. The notion and definition of traditional knowledge varies across geography, disciplines, and peoples, however, is becoming increasingly recognized as valuable information and knowledge in the area of polar science in particular. Discussions pertaining to traditional knowledge also relate to local knowledge, indigenous knowledge or traditional ecological knowledge.
Traditional Knowledge has many definitions, however the core definition is well described by an elder fromjpg Tuktoyaktuk in the Inuvialuit Settlement Region: Traditional Knowledge is the pride in knowing your culture and knowing how to survive in your surroundings. Traditional Knowledge is a rich knowledge base, it is knowledge gained from the experience of living on the land and knowledge passed down by ancestors, and it takes a holistic approach to understanding the environment. As science often takes a reductionist approach to understanding the environment, using Traditional Knowledge and scientific knowledge together creates a more in-depth understanding of ecosystems or species of study.
See some of our additional pages on this topic:
Ecological research in polar regions explores interactions between various groups of organisms, as well as relations that they have with respect to their environment. Despite the apparent harshness of the Arctic and Antarctic, many creatures are well adapted to living "at the edge". Ecosystems of the tundra biom are not as simple and primitive as it may seem!
Polar organisms are now facing a threat much more difficult to cope with than extreme cold, drought and darkness - a rapidly changing climate. Increasing air temperature causes melting of glaciers and permafrost, changes in water relation and growing season. These changes affect all ecosystem components. New ecosystems are forming in areas uncovered from under the ice, whereas at the southern borders of the Arctic shrub and tree expansion is underway, reducing the extent of the tundra. Great research effort is put to monitor the speed and direction of these changes, to provide effective conservation of the fragile tundra ecosystems.