Polar (change) Explorer

Cloud-aerosol interactions

Aerosol particles change cloud properties by acting as cloud condensation nuclei and ice-nucleating particles, thus influencing the Antarctic climate system.
PolarRES is investigating the importance of persistent localised areas of open water as sources of aerosols (e.g., polynyas and leads) and their potential to alter properties such as cloud droplet number, and whether this has an impact on clouds and subsequently the climate.

Albedo & surface energy balance

The balance between the amount of solar radiation reflected and absorbed by the Earth's surface, which is determined by albedo, plays an essential role in regulating global temperature and climate. The positive albedo feedback due to the reduction of sea ice and more open water (lower albedo, less reflection of solar radiation) is one of the main drivers of the so-called Arctic warming amplification.
By coupling at high resolution polar regional atmospheric climate models with regional ocean models, PolarRES is developing a better understanding and quantifications of how the sea-ice-atmosphere interactions, including the albedo feedback, will enhance the Arctic warming.

Internal melting of Antarctic landfast sea ice resulting in gap layer formationCharacteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19

Wind forcing on sea ice drift

Sea ice, including snow on top of it, is primarily driven by winds. As a result, sea ice is typically being formed in a different location than where it melts. Additionally, snow drifts with wind forming sastruga and a portion ending to open water between ice floes. In the Antarctic, it is common that ice motion is divergent and the role of internal ice stress is small.

Impacts of strong wind events on sea ice and water mass properties in Antarctic coastal polynyas.

Atmospheric boundary layer (ABL) turbulence

The ABL is the lowermost layer of the atmosphere, which reacts to changes in Earth surface properties (such surface temperature and roughness) on time scales shorter than a day. In the Antarctic, the ABL depth varies from a few tens of hundred metres to 1 km. The state of the ABL depends on the radiative and turbulent energy fluxes at the Earth’s surface and on the heat conduction from the snow, ice or ground. Over snow and ice in the Antrctic, the ABL is often stably stratified (weak turbulence), but over areas of open water (coastal polynyas and leads in the sea ice zone, and glacial lakes on the continent) a convective ABL (stronger turbulence) is typical.

Evaporation over a glacial lake in AntarcticaThe generation of linear and nonlinear internal waves forced by sub-inertial tides over the Yermak Plateau, Arctic Ocean

Extreme temperature & precipitation events

The coastal zone of the Antarctic Peninsula and West Antarctica are influenced by extreme precipitation, temperature, and surface melt episodes, which are poorly understood. The objective of PolarRES work is to disentangle the role of large-scale forcing (i.e., warm/moist air advection) versus local dynamics (e.g., induced by the complex coastal orography).

Characteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19Characteristics of surface “melt potential” over Antarctic ice shelves based on regional atmospheric model simulations of summer air temperature extremes from 1979/80 to 2018/19Climate projections over the Antarctic Peninsula region to the end of the 21st century. Part III: clouds and extreme precipitationVariability of extreme precipitation in West Antarctica and its response to the Amundsen Sea Low changes

Heat, water vapour and aerosol fluxes

In coastal polynyas, the latent heat from forming sea ice is discharged to cold winter atmosphere. At the same time, brine is rejected from forming sea ice to the upper ocean where, together with the freezing temperatures, the formation of the densest watermass in the World Ocean, the Antarctic Bottom Water occurs. This water mass is an important component of the global overturning circulation.

A change in the relation between the Subtropical Indian Ocean Dipole and the South Atlantic Ocean Dipole indices in the past four decades

Katabatic winds

The katabatic wind is a drainage wind, a wind that carries high-density air from a higher elevation down a slope under the force of gravity.

Impacts of strong wind events on sea ice and water mass properties in Antarctic coastal polynyas.Seasonal and interannual variability of the landfast ice mass balance between 2009 and 2018 in Prydz Bay, East Antarctica.

Ocean acidification

The process of decreasing ocean pH, and carbonate ion content, occurring when CO2 gas reacts with sea water. Ocean acidification is today a problem due to the high rate of increase in atmospheric CO2, and the ocean’s inability to replenish the carbonate ion reservoir quickly enough. Ocean acidification is in particular a problem for a variety of calcifying marine organisms, such as coccolithophores and corals, bivalves, fish, and crustaceans, which will struggle to form and repair their exoskeletons.

Status, Change, and Futures of Zooplankton in the Southern Ocean

Basal melt of ice shelves

The basal melt of ice shelves is a key factor governing ice discharge from the Antarctic Ice Sheet. The melting point of water decreases under pressure, meaning that water melts at a lower temperature under thicker glaciers.

Opening & closing of coastal polynyas

Coastal polynyas represent areas of increased biological productivity in ice-covered seas and form a vital habitat for many Antarctic species. The life cycles of many zooplankton, marine mammals, and seabirds are closely associated with the timing of their opening and closing.

Status, Change, and Futures of Zooplankton in the Southern Ocean The thermodynamic and dynamic control of the sensible heat polynya in the western Cosmonaut Sea.Impacts of strong wind events on sea ice and water mass properties in Antarctic coastal polynyas.The response of sea ice and high-salinity shelf water in the Ross Ice Shelf Polynya to cyclonic atmosphere circulations

Antarctic bottom water

Antarctic bottom water is an important water mass that forms on the Antarctic continental shelf as a cold, dense residual brine during the formation of sea ice.

Status, Change, and Futures of Zooplankton in the Southern OceanThe response of sea ice and high-salinity shelf water in the Ross Ice Shelf Polynya to cyclonic atmosphere circulations

CO2 flux

The rate of exchange of CO2 between Earth's surface and the atmosphere.

Polar jet stream

The polar jet stream is a belt of powerful upper-level winds that sits atop the polar front. The winds are strongest in the tropopause, which is the upper boundary of the troposphere, and move in a generally westerly direction in mid-latitudes.

Linking the Antarctic sea ice extent changes during 1979-2020 to seasonal modes of Antarctic sea ice variability.

Stratospheric polar vortex

A large-scale low pressure system between ~10-50 km altitude centred over the pole. This feature is characterised by westerly winds surrounding the Antarctic continent for much of the year, except in summer. The polar vortex is likely to strengthen in the future due to an enhanced pole-to-equator temperature gradient, as well as breakdown later in late spring/early summer, but climate models disagree by how much. This impacts the strength and location of the jet stream in the troposphere, which in turn influences the climate change response in the Antarctic.

Future Antarctic Climate: Storylines of Southern Hemisphere mid-latitude jet strengthening and shift emergent from CMIP6

Antarctic Circumpolar Current (ACC)

The Southern Ocean flows clockwise around the Antarctic continent and is dominated by the Antarctic Circumpolar Current (ACC). This is the worlds coldest, biggest, and fastest current, and the only current that flows completely around the globe. The ACC is characterised by a series of frontal systems, which separate the colder surface waters of the Southern Ocean from the warmer waters and oceans north of it. These physical features are key drivers of biology and ecological connectivity across the Southern Ocean, signifying the vulnerability of Southern Ocean biota, including zooplankton, to climate change.

Status, Change, and Futures of Zooplankton in the Southern Ocean

Dynamical stratosphere-troposphere coupling

The dynamical coupling between the stratosphere and the troposphere (via various atmospheric waves and the large-scale circulation) is an important source of atmospheric variability, as well as extreme weather.