Preface

Glaciers and polar regions provide important clues to understanding the past and present status of the Earth system, as well as to predict future forms of our planet.

In particular, Antarctica, composed of an ice-covered continent in its center and surrounded by the Southern Ocean, has been gradually investigated during the last half century by all kinds of scientific branches; bioscience, physical sciences, geosciences, oceanography, environmental studies, together with technological components. Antarctica is now affected by remarkable changes in its temperature and sea-ice extent, mass loss of ice-sheets, variations in marine and terrestrial ecosystems including human activities. Since the most exciting initiative in the polar regions was the International Polar Year (IPY) in 2007-2008, conducted as the 50th anniversary of the International Geophysical Year (IGY 1957-1958). The initiative greatly enhanced the exchange of ideas across nations and scientific disciplines to unveil the status and changes of planet Earth. This kind of inter-disciplinary exchange helps us understand and address grand challenges such as rapid environmental change and its impact on society. In these regards, this book partially aims to compile the achievements of involved projects by the IPY and post era, especially focusing on surface environmental variations associated with climate change.

On the other hand, mountain glaciers are primary sources of freshwater for the population and they sustain the local economies in terms of water supply for agriculture, energy production, and tourism activities. They are suffering due to global warming at a large extent and many low-altitude glaciers are expected to disappear within the next decades. The rapid reduction of the glaciated areas threatens to enhance potential draughts and to modify the distribution, frequency, and magnitude of glacier-related hazards. Moreover, glacial ecosystems and biodiversity might be strongly damaged. For these reasons, the glacier environment has to be carefully studied and monitored, in order to evaluate their possible recent evolution and to implement strategies of resilience, adaptation, and mitigation.

This book covers topics on recent developments of all kinds of scientific research involving glaciers and Antarctica, in the context of currently on-going processes in the extreme environment in polar regions.

**II**

**Chapter 9 167**

Variations of Lys Glacier (Monte Rosa Massif, Italy) from the Little Ice Age

*by Fugazza Davide, Senese Antonella, Azzoni Roberto Sergio, D'Agata Carlo, Cat Berro Daniele, Mercalli Luca, Ventura Fabiano, Smiraglia Claudio* 

to the Present from Historical and Remote Sensing Datasets

*and Diolaiuti Guglielmina Adele*

**Masaki Kanao** Associate Professor, National Institute of Polar Research, Tokyo, Japan

**Danilo Godone and Niccolò Dematteis** Research Institute for Geo-Hydrogeological Protection, National Research Council, Turin, Italy

**1**

**Chapter 1**

**Abstract**

**1. Introduction**

Gas Hydrates in Antarctica

Few potential distributing areas of gas hydrates have been recognized in literature in Antarctica: the South Shetland continental margin, the Weddell Sea, the Ross Sea continental margin and the Wilkes Land continental margin. The most studied part of Antarctica from gas hydrate point of view is the South Shetland margin, where an important gas hydrate reservoir was well studied with the main purpose to determine the relationship between hydrate stability and environment effects, including climate change. In fact, the climate signals are particularly amplified in transition zones such as the peri-Antarctic regions, suggesting that the monitoring of hydrate system is desirable in order to detect potential hydrate dissociation as predicted by recent modeling offshore Antarctic Peninsula. The main seismic indicator of the gas hydrate presence, the bottom simulating reflector, was recorded in few parts of Antarctica, but in some cases it was associated to opal A/ CT transition. The other areas need further studies and measurements in order to

**Keywords:** gas hydrate, BSR, Antarctic Peninsula, climate change, opal A/CT

Gas hydrate is a solid component (clathrates) composed of water and natural gas of low molecular weight (mainly methane), forming under particular condition of low temperature, high pressure, and proper gas concentration [1]. Pressure and temperature define the stability field of gas hydrate, which is affected by gas mixture and pore-fluids composition (salinity). Moreover, the presence of only a small percentage of higher hydrocarbons (such as ethane and propane) shifts the phase boundary to higher temperature (at constant pressure). Generally, hydrates accumulate anywhere in the ocean-bottom sediments where water depth exceeds about 400 m (**Figure 1**). In Polar Regions, in presence of sub-seawater permafrost, the hydrate could be stable at shallower water as demonstrated recently by [2, 3]. Very deep (abyssal) sediments are generally not thought to house hydrates in large quantities due to the lack of high biologic productivity (necessary to produce the organic matter that is converted to methane) and rapid sedimentation rates (necessary to bury the organic matter), both necessary for hydrate formation on the continental shelves. The conditions for gas hydrate stability are verified also in seawater, but gas

Gas hydrates were discovered in 1810 by Humphry Davy [4] and, since then, they became the interest of scientific and engineering research studies. In fact, the stability of methane hydrates on the sea floor has several implications (i.e., "in [5, 6]"). First, they are considered a huge energy resource (i.e., "in [7]"). Second, natural and anthropogenic disturbances may cause their destabilization causing the

*Michela Giustiniani and Umberta Tinivella*

confirm or refuse the gas hydrate presence.

concentration is always not sufficient for their formations.
