An ice mass balance buoy (IMB) allows scientists studying sea ice to measure its temperature and the evolution of its interfaces remotely. The autonomous mass balance buoys usually consist of a data controller module and a temperature string. Some ice mass balance buoys also include acoustic sounders above and below ice measuring the positions of the snow-ice and ice-water interfaces.
The main types of ice mass balance buoys include
The CRREL-Dartmouth Ice Mass Balance Buoy (IMB) includes two ice-facing acoustic rangefinders, a vertical temperature string, and air temperature and pressure sensors. These sensors are connected to a non-floating satellite-connected transmission package. Seasonal Ice Mass Balance Buoy (SIMB-1). The SIMB-1,2,3 instruments have the same sensor package as the CRREL-Dartmouth IMB but are enclosed in a spar-type buoy hull to improve their performance during the melt season. The lower-budget Snow and Ice Mass Balance Array (SIMBA) from SAMS includes only a vertical temperature string and a non-floating satellite-connected transmission package.
The main part of IMBs is a vertical chain of thermistors. The vertical spacing of the thermistors at modern IMBs is usually around 2–4 cm. The accuracy of each sensor is generally within 0.1–0.5°C. Many modern IMBs measure in-situ temperatures and temperatures after a cycle of internal heating. In experimental fluid dynamics, such a mode is called a “hot-wire anemometer”. In IMBs, the heat is added by applying an excitation voltage to the resistor bonded to the temperature sensor. The temperature response of the sensor during heating depends on the thermal diffusivity of the surrounding medium (for solids like snow or ice) and the flow rate of the medium (for fluids like seawater or air). The heat transfer in fluids depends on the fluid velocity, and the response usually varies over time scales. The measurements of the temperature response to heating may be used to discriminate different layers within the air-snow-ice-ocean system.
The thermistor chain is usually installed in a standard hole produced by a 2-inch auger. A weight is attached to the bottom end to keep it straight. The data is returned after each sample using the Iridium SBD system. During the deployment, the manual measurements of snow thickness, ice draft and freeboard, and location of IMB sensors are usually made. The IMB deployment disturbs the system around sea ice. For example, snow may have poor contact with the thermistor chain. Additionally, the 2-inch hole may refreeze very slowly if the air temperatures are high or the snow is deep. In summer, the presence of the chain may lead to receiving additional solar energy absorption, which may influence the rates of snow and ice melt.
IMBs were used in several Arctic and Antarctic expeditions, including the SHEBA expedition in Beaufort Gyre, N-ICE2015 expedition north of Svalbard, and the MOSAiC expedition across Transpolar drift.
The usage of IMBs revealed that in the Central Arctic regions with high sea ice concentration, surface and bottom ice melt are comparable. In contrast, in regions with low sea ice concentration, the amount of ice bottom melt is substantially larger. [5] IMBs can be also used to show spatial and temporal variability of sea ice growth and melt, also providing an estimate of ocean heat fluxes [6] IMBs can also be used for studying pressure ridges for analysis of their winter consolidation rates, [7] for analysis of ridge consolidation during their warming, [8] and to study effects of snow slush contribution to the ridge consolidation. [2] IMBs also allow the study of the temporal evolution of under-ice meltwater layers, conditions of false bottom formation, and their effect on ice melt rates. [1]
The cryosphere is an all-encompassing term for the portions of Earth's surface where water is in solid form, including sea ice, lake ice, river ice, snow cover, glaciers, ice caps, ice sheets, and frozen ground. Thus, there is a wide overlap with the hydrosphere. The cryosphere is an integral part of the global climate system with important linkages and feedbacks generated through its influence on surface energy and moisture fluxes, clouds, precipitation, hydrology, atmospheric and oceanic circulation.
Sastrugi, or zastrugi, are features formed by erosion of snow by wind. They are found in polar regions, and in snowy, wind-swept areas of temperate regions, such as frozen lakes or mountain ridges. Sastrugi are distinguished by upwind-facing points, resembling anvils, which move downwind as the surface erodes. These points usually lie along ridges parallel to the prevailing wind; they are steep on the windward side and sloping to the leeward side. Smaller irregularities of this type are known as ripples or wind ridges.
Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface. Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans. Much of the world's sea ice is enclosed within the polar ice packs in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, including the ocean's ecosystems. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean. Depending on location, sea ice expanses may also incorporate icebergs.
An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The boundary between the floating ice shelf and the anchor ice that feeds it is the grounding line. The thickness of ice shelves can range from about 100 m (330 ft) to 1,000 m (3,300 ft).
The Greenland ice sheet is a body of ice with the thickness of about 1.67 km (1.0 mi) on average, and almost 3.5 km (2.2 mi) at its thickest point. It is almost 2,900 kilometres (1,800 mi) long in a north–south direction, with the greatest width of 1,100 kilometres (680 mi) at a latitude of 77°N, near its northern margin. It covers 1,710,000 square kilometres (660,000 sq mi), around 80% of the surface of Greenland, and is the second largest body of ice in the world, after the East Antarctic ice sheet. It is sometimes referred to as an ice cap, or under the term inland ice, or its Danish equivalent, indlandsis. The acronyms GIS or GrIS are also frequently used in the scientific literature.
Ice algae are any of the various types of algal communities found in annual and multi-year sea, and terrestrial lake ice or glacier ice.
The Cold Regions Research and Engineering Laboratory (CRREL) is a United States Army Corps of Engineers, Engineer Research and Development Center research facility headquartered in Hanover, New Hampshire, that provides scientific and engineering support to the U.S. government and its military with a core emphasis on cold environments. CRREL also provides technical support to non-government customers.
A pressure ridge, when consisting of ice in an oceanic or coastal environment, is a linear pile-up of sea ice fragments formed in pack ice by accumulation in the convergence between floes.
Major environmental issues caused by contemporary climate change in the Arctic region range from the well-known, such as the loss of sea ice or melting of the Greenland ice sheet, to more obscure, but deeply significant issues, such as permafrost thaw, as well as related social consequences for locals and the geopolitical ramifications of these changes. The Arctic is likely to be especially affected by climate change because of the high projected rate of regional warming and associated impacts. Temperature projections for the Arctic region were assessed in 2007: These suggested already averaged warming of about 2 °C to 9 °C by the year 2100. The range reflects different projections made by different climate models, run with different forcing scenarios. Radiative forcing is a measure of the effect of natural and human activities on the climate. Different forcing scenarios reflect things such as different projections of future human greenhouse gas emissions.
Polar meteorology is the study of the atmosphere of Earth's polar regions. Surface temperature inversion is typical of polar environments and leads to the katabatic wind phenomenon. The vertical temperature structure of polar environments tends to be more complex than in mid-latitude or tropical climates.
The climate of the Arctic is characterized by long, cold winters and short, cool summers. There is a large amount of variability in climate across the Arctic, but all regions experience extremes of solar radiation in both summer and winter. Some parts of the Arctic are covered by ice year-round, and nearly all parts of the Arctic experience long periods with some form of ice on the surface.
The Arctic Ocean is the smallest and shallowest of the world's five major oceans. It spans an area of approximately 14,060,000 km2 (5,430,000 sq mi) and is known as one of the coldest of oceans. The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea. It has also been described as an estuary of the Atlantic Ocean. It is also seen as the northernmost part of the all-encompassing World Ocean.
Measurement of sea ice is important for safety of navigation and for monitoring the environment, particularly the climate. Sea ice extent interacts with large climate patterns such as the North Atlantic oscillation and Atlantic Multidecadal Oscillation, to name just two, and influences climate in the rest of the globe.
Frost flowers are ice crystals commonly found growing on young sea ice and thin lake ice in cold, calm conditions. The ice crystals are similar to hoar frost, and are commonly seen to grow in patches around 3–4 cm in diameter. Frost flowers growing on sea ice have extremely high salinities and concentrations of other sea water chemicals and, because of their high surface area, are efficient releasers of these chemicals into the atmosphere.
Sea ice is a complex composite composed primarily of pure ice in various states of crystallization, but including air bubbles and pockets of brine. Understanding its growth processes is important for climate modellers and remote sensing specialists, since the composition and microstructural properties of the ice affect how it reflects or absorbs sunlight.
The Surface Heat Budget of the Arctic Ocean (SHEBA) study was a National Science Foundation-funded research project designed to quantify the heat transfer processes that occur between the ocean and the atmosphere over the course of a year in the Arctic Ocean, where the sun is above the horizon from spring through summer and below the horizon the rest of the time. The study was designed to provide data for use in global climate models, which scientists use to study global climate change.
The Arctic ice pack is the sea ice cover of the Arctic Ocean and its vicinity. The Arctic ice pack undergoes a regular seasonal cycle in which ice melts in spring and summer, reaches a minimum around mid-September, then increases during fall and winter. Summer ice cover in the Arctic is about 50% of winter cover. Some of the ice survives from one year to the next. Currently, 28% of Arctic basin sea ice is multi-year ice, thicker than seasonal ice: up to 3–4 m (9.8–13.1 ft) thick over large areas, with ridges up to 20 m (65.6 ft) thick. Besides the regular seasonal cycle there has been an underlying trend of declining sea ice in the Arctic in recent decades as well.
The Multidisciplinary drifting Observatory for the Study of Arctic Climate expedition was a one-year-long expedition into the Central Arctic. For the first time a modern research icebreaker was able to operate in the direct vicinity of the North Pole year round, including the nearly half year long polar night during winter. In terms of the logistical challenges involved, the total number of participants, the number of participating countries, and the available budget, MOSAiC represents the largest Arctic expedition in history.
Jacob Sebastian Haugaard Mernild is a Danish professor in climate change, glaciology and hydrology, who is the pro-vice-chancellor of the University of Southern Denmark. Mernild has been an Intergovernmental Panel on Climate Change (IPCC) author for the United Nations since 2010. Initially a contributing author on the IPCC Fifth Assessment Report, he was lead author on the IPCC Sixth Assessment Report.
False bottom is a form of sea ice that forms at the interface between meltwater and seawater via the process of double-diffusive convection of heat and salt.