El positivismo jurídico y las teorías del derecho natural

 THE END OF SNOWY HEIGHTS? Glaciers and Climate Change in the Andean Community

Concerning climate change scenarios for the XXI century and their relation with glacier retreat, general circulation models -under the hypothesis that greenhouse gas concentration double- foresee a generalized increase of temperatures in the Central Andes, which would be even higher above 4.000 masl. This increase in temperature would produce temporary increase of river flows located in glacier watersheds, followed by a drastic decrease of water volume. The hydrological regime will depend more and more on snow and rain as glaciers disappear, starting with the smaller ones and with those of lower altitude.

Although important progress has been made in the study of glaciers and their relation with climate change, it is important to continue with them and expand them all over the region (glaciers from several massifs). It would be very interesting to make an effort to build a Climate Change Scientific Research Agenda for the Andean subregion, that highlights research priorities as a base for policy development, planning tools and guidelines for investment, that take into account possible climate change impacts.

This Agenda would become a guideline for the scientific community and may be used as a reference to concentrate efforts and resources. Some topics that could be prioritized in this agenda are:

• Water availability in glacial basins and estimation of costs of the impacts on population, power generation, farming and productive activities.

• Glacier retreat impact in the Amazon area.

• Glacial lakes inventory and determination of risk for neighbouring populations and activities.

• Documentation of past glacier evolution as a reference to compare projections on their future evolution. • Effect of the Pacific Ocean on the Andean glaciers and

how it combines with atmosphere heating trends. Finally, a basic and priority issue for climate change research and management in the region is to strengthen the hydro-meteorological observation network in the Andean region (with special emphasis on glacial basins) with some monitoring stations located above 5.000 m.a.s.l.

Glossary

25 _{Extract from B.Francou and C.Vincent, op. cit.}

Ablation: The process by which a glacier loses mass. Losses of surface come from an energy input from the atmosphere. Part of the ablation, limited in its amount except in volcanic regions, comes from ground heat (geothermal flow) and mechanical efforts due to deformations undergone by ice. The ablation zone, where ablation exceeds accumulation along the years, makes up the lower part of the glacier. This zone varies from year to year.

Accumulation: The process by which the glacier accumulates mass, essentially thanks to solid falls gathered on its surface. Accumulation also comprises frost input, snow displacement due to wind, avalanches and melts coming from steep walls. The accumulation zone in a glacier is the region where deposits resist ablation along a year. The extension of the glacier accumulation zone varies from year to year with mass balance.

Albedo: It comes from Latin albedo with means whiteness. It designates the power a body has to reflect received radiation. Albedo reaches 1 when all the radiation is reflected, or 0 when all the radiation is absorbed, as a perfectly black body. In a glacier surface, albedo is usually between 0.8 (fresh snow) and 0.4 (ice which has not been covered by mineral or organic detritus). Albedo plays a primary role in a glacier’s energy balance and, more generally, in the Earth’s.

Calving: Glacier substance loss that reaches the sea or a lake due to iceberg release. Calving can have much influence on the glacier’s mass balance or its dynamic.

Emissary Torrent (river): Torrent that comes out from the glacier’s front. In tempered glaciers (ice with fusion temperature at rocky bed level), the torrent is sub-glacier and runs off the rocky bed surface, while in cold glaciers (ice with negative temperature at rocky bed level), the torrent runs off the surface or at little depth.

Energy Balance: This balance consists of quantifying every energy input and loss. These flows maybe radiative (short and long waves), turbulent (linked to atmosphere movement and water phase changes) or conductive (heat condition of the ground). Energy balance on the surface includes snow or ice fusion.

Firn: Firn can be defined as the material which intensity is comprised between 0.55 g/cm3 _{and ice intensity. However,}

some authors call firn a snow that is more than one year old. Firn becomes ice within a density range of 0.8-0.84 g/cm3_.

Front (of a glacier): Last end of the glacier which is subject to progression or regression according to surface mass balance and ice input from the high section. In tempered glaciers a torrent frequently comes out of its front due to contact between ice and rocky bed. A large part of the coarse rocky waste transported by the glacier which is not gathered by the emissary torrent are left at the front making up important frontal moraines when the front stays at the same place for a long time.

Fusion (or melting): Transformation of ice or snow into water. This process requires an energy of 334,000 Joules per kilogram. Fusion is the dominant ablation process in glaciers, mainly when the atmosphere has a positive temperature, when it is humid and several low intensity winds cross it. Glacier: Hectometric or greater ice mass, permanent at human scale, deformed under its own weight. This mass moves at an annual speed estimated in meters or kilometers on the surface. A glacier may be shaped as a dome (glacier cask), a fan, with rocky crests at the summit (circus glacier), a block suspended from a tilted wall (suspended glacier) or forming a very long tongue that snakes into a valley (valley glacier). These shapes can be combined, for example, a cask

 THE END OF SNOWY HEIGHTS? Glaciers and Climate Change in the Andean Community

above which ice evacuates to the borders through individual tongues (exutory glaciers or cask emissions). Glaciers vary constantly in surface, volume and speed, as a response to their mass balance and other local factors.

Glacier equilibrium line: Line joining the point of a glacier where mass balance is null, thus limiting the accumulation zone and the ablation zone of a glacier. Equilibrium Line Altitude (ELA) is negatively correlated with the glacier’s mass balance.

Hydrological Year: Year cut based upon precipitation distribution and river drain off. Hydrological year starts when water reserves in a basin reach their minimum levels. In mid and high altitudes (Alpes, Alaska), the hydrological year in basins with glaciers starts when average accumulation on said glaciers exceeds ablation. Under the tropics and in the regions where rain falls during the summer (Tien Shan, Tibet), the hydrological year starts while accumulation grows in the higher parts of glaciers and ablation also grows in the lower parts of glaciers. Under the Equator (e.g in Ecuador), however, this periodicity can be quite erroneous.

Isotope: Atoms from a same element whose nuclei have different masses. Stable isotopes are used to reconstruct past temperatures or rainfall from the ratio between other isotopes of the same element (example 18_O/16_{º or ratio}

between oxygen isotopes 18 and 16). Radiative isotopes are used as dating tools by measuring disintegration duration (example: 14_{C or isotope 14 of carbon).}

Latent heat flow: Energy flow linked to water phase changes (solid, liquid, gaseous). These changes require a large demand of energy; for example, 334,000 joules are necessary to melt one kilo of ice and 2’834,000 joules to sublimate one kilo of ice (almost 8.5 times more).

Mass Balance: It is defined as the difference between accumulation (solid falls, frost, wind contributions) and ablation (fusion, sublimation, calving) along time, generally a hydrological year. It is expressed in cubic meters, ice or water equivalent tons, estimating snow, firn, or ice material density. Mass balance in a period maybe positive (mass gain), negative (mass loss) or balanced.

Moraine (morrenic): A term designating the detritic mass transported by the glacier and deposited at the borders and in contact with the rocky bed. Moraines make deposits in lengthened and continuous bands on the glacier’s surface, called, according to their position, mid, lateral or frontal moraines. They are called internal moraine in the ice and, under it, bottom moraines. They can also cover the glacier’s surface regularly in its ablation zone (ablation moraine). This happens more in back glaciers. Frontal and lateral moraines are used to rebuild surfaces and eventually the volumes occupied by glaciers after they recede.

Radiation emission wavelength: radiation emitted by the sun (6,000 ºK) and by the earth (255 ºK) distributed in different wavelength bands. Sun radiation is within 0.2-0.4 µm (ultraviolet radiation), 0.4-0.8 µm (visible radiation) and 0.8-5 µm (near infrared). The Earth’s emission is essentially infrared (5-100 µm). The ultraviolet radiation from the sun is stopped by stratosphere ozone, but its visible light is not much filtered by the atmosphere. Infrared radiations coming from the Earth’s surface are stopped by greenhouse effect gases, that is, water vapor, carbon dioxide, methane, nitrogen protoxyde, troposphere ozone, etc.

Radiative Balance: It is the difference between incident solar radiation and radiation emitted by the ground. Making the radiative balance of a glacier or a planet consists of quantifying these exchanges and their balance.

Sensitive heat flow: Heat transferred through conversion between surface and water. This flow is linked to air turbulence (wind) and air temperature.

Sublimation: Ice loss in the vapor phase. This process requires a large amount of energy equivalent to 2,834,000 Joules per kg, that is, approximately 8.5 times more than fusion. Sublimation is very important in media where atmosphere is dry and windy. It participates in shaping ice and snow penitents.

Troposphere: Low atmosphere layer measuring between 7 km (close to the poles) and 15 km (close the equator). Its temperature lowers as one ascends.

Turbulent flows: Sensitive heat and latent heat flow are non-radiative flows linked to air turbulence that are exchanged between atmosphere and ground surface.

 THE END OF SNOWY HEIGHTS? Glaciers and Climate Change in the Andean Community