**2.4 Modeling of gas hydrate versus climate change**

In the past years, scientists are taking an interest in modeling warming-induced hydrate dissociation in the Antarctic region. Over the period 1958 to 2008, the Antarctic Peninsula shows an unusually high rate of warming [42], the strongest of the Southern Hemisphere and one of three strongest on Earth [43]. Predicting future warming in this area is challenging because of the lack of a sound physical mechanism that explains the present regional warming [43], but some models predict that in the 21st century the Antarctic Peninsula may not experience the strongest warming of Antarctica [44]. Ocean warming in West Antarctica is predicted to be of 0.5 ± 0.4° C by 2100, about half of global mean warming, considering the A1B scenario [45], which assumes modest reductions in greenhouse-gas emissions after mid-21st century. A long-term ocean warming similar to that predicted in West Antarctica may be sufficient to trigger dissociation of a shallow hydrate reservoir in the SSM. This hypothesis has been preliminary tested by [22] based on steady-state modeling of the evolution of the base of the hydrate stability zone assuming a 1.4° C increase by the end of the 21st century.

**9**

**Figure 7.**

Successively, it was modeled the transient response to ocean warming of the hydrate system in the SSM between 375 and 450 mwd for the period 1958–2100 CE,

using constraints in input parameters from seismic observations [22, 46].

*Map of the gas hydrate concentrations at different depth from seafloor (in meters).*

*Gas Hydrates in Antarctica*

*DOI: http://dx.doi.org/10.5772/intechopen.94306*

*Glaciers and the Polar Environment*

underlined between the HP values and the distance from the hinge of the anticline: the HP increases toward the limbs of anticline. The microfracturing model supports the idea that the synclines favors the hydrate accumulation above the BSR, while the anticlines favors the free gas accumulation below the BSR, when important faults

*Example of ancient slides highlighted with a black dash lines on the bathymetric data. The position of the two* 

All available seismic profiles and OBS data were analyzed in order to obtain 2D seismic velocity models, then translated in terms of concentrations of gas hydrate and free gas in the pore space by using Tinivella theoretical models [37, 38]. The jointly interpolation of the 2D models allowed obtaining a 3D model of gas hydrate concentration from the seafloor to the BSR, as shown in **Figure 7**. The total volume

. The gas hydrate concentration is affected by error estimated equal to

of free gas in standard conditions, the total free gas trapped in this

about ±25%, as deduced from sensitivity tests and from error analysis related to the interpolation procedure. The estimated amount of gas hydrate can vary in a range

. Moreover, considering that 1 m3

into account the free gas contained within pore space below the hydrate layer, so

hydrate dissociation in the Antarctic region. Over the period 1958 to 2008, the Antarctic Peninsula shows an unusually high rate of warming [42], the strongest of the Southern Hemisphere and one of three strongest on Earth [43]. Predicting future warming in this area is challenging because of the lack of a sound physical mechanism that explains the present regional warming [43], but some models predict that in the 21st century the Antarctic Peninsula may not experience the strongest warming of Antarctica [44]. Ocean warming in West Antarctica is predicted to be of 0.5 ± 0.4° C by 2100, about half of global mean warming, considering the A1B scenario [45], which assumes modest reductions in greenhouse-gas emissions after mid-21st century. A long-term ocean warming similar to that predicted in West Antarctica may be sufficient to trigger dissociation of a shallow hydrate reservoir in the SSM. This hypothesis has been preliminary tested by [22] based on steady-state modeling of the evolution of the base of the hydrate stability zone assuming a 1.4° C

In the past years, scientists are taking an interest in modeling warming-induced

) where the interpolation is reliable, is

of gas hydrate corresponds

. This estimation does not take

acting as preferential path-way for fluids escapes [40].

*zoom is reported in Figure 3. The bathymetric data scale is reported in Figure 3.*

of hydrate, estimated in the area (600 km2

m3

this values could be underestimated [41].

increase by the end of the 21st century.

reservoir ranges between 1.68 × 1012 and 2.8 × 1012 m3

**2.4 Modeling of gas hydrate versus climate change**

16 × 109

**Figure 6.**

of 12 × 109

to about 140 m3

m3

–20 × 109

**8**

#### **Figure 7.**

*Map of the gas hydrate concentrations at different depth from seafloor (in meters).*

Successively, it was modeled the transient response to ocean warming of the hydrate system in the SSM between 375 and 450 mwd for the period 1958–2100 CE, using constraints in input parameters from seismic observations [22, 46].

TOUGH-HYDRATE (T-H) code [47] was employ for the modeling, with past temperatures given by the US National Oceanographic Data Center and two future temperature scenarios given by extrapolation of the temperature trends over the periods 1960–2010 and 1980–2010. The result of the transient modeling shows that methane emissions may occur at water depths between 375 m and 425 m if the future seabed temperatures follow a similar trend to that over the period 1980 to 2010 of 0.0238° C y-1), while emissions would not occur with a seabed warming rate an order of magnitude smaller [46]. Hydrate dissociation would initiate at the top of the hydrate layer, and the overpressure generated would not be sufficient to cause, by itself, shallow slope failures or shallow vertical fractures over the 21st century. Hydrate-sourced methane emissions at 375 mwd would start at ca. 2028 and may extend to deeper waters at an average rate of 0.91 mwd y−1. Over the 21st century, the potential amount of dissociated methane liberated to the ocean may be between 1.06 and 1.21–103 mol y−1 per meter along the margin [46]. This modeling underlines that the SSM is one of the key areas to observe and understand the effects of warming-induced hydrate dissociation in the Southern Hemisphere during the coming decades [46].
