**4. Wilkes Land margin**

*Glaciers and the Polar Environment*

be between 1.06 and 1.21–103

during the coming decades [46].

**3. Weddell Sea**

Arctic [53].

hydrate stability zone.

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

eling 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

The Weddell Sea is considered a potential area for gas hydrate accumulation (i.e., "in [48]"), even if a clear indication of hydrate presence is missed. It is important to underline that, in this part of Antarctica, acquisition of data was very difficult in the past due to presence of ice shelves. Only in the last years, the extraordinary rapid climate warming, which is occurring in the northern tip of the Antarctic Peninsula [49, 50], caused the reduction of land ice along West Antarctica and the ice shelves destruction in the surrounding seas (i.e., "in [51, 52]"). In north-western of Weddell Sea, [53] detected the presence of gaseous hydrocarbons (from methane to n-pentane) in the seabed sediments and the bubbling of methane suggesting the presence of gas accumulations in the substrate of the NW Weddell Sea. They observed a release of methane from the frozen ocean substrate adjacent to Seymour Island, linked to climate instability during Late Cenozoic, when vast areas of the Antarctic continental shelf were flooded during the marine transgression that occurred . 18,000 years ago, after the Last Glacial Maximum. The heat flow from the sea to the marine substrate, now flooded, would have destabilized frozen gas accumulations, which were originally formed into terrestrial permafrost during the Last Glacial Maximum, similarly to what would have happened in the

Seismic data acquired in 1985 over the south-eastern continental shelf and the margin of the South Orkney microcontinent as a site survey for ODP Leg 113 [54], show a BSR lying at 500–800 ms. The widespread cause of the reflection was interpreted as a break-up unconformity associated with the 25–30 Ma opening of the Jane Basin to the east [55]. In places, the detected BSR cuts across beddings, and in this case this physical boundary may be either depositional or of secondary origin related to the diagenesis of biogenic silica, possibly combined with a major variation of the detrital input [56]. So, also in this case, the BSR is not produced by gas hydrate and free gas presence, suggesting that a careful analysis of seismic data is necessary before to interpret a BSR as the base of gas

So, potentially, in this area, all conditions to have gas hydrate are verified, even if

the small amount of data acquired cannot confirm or reject this hypothesis.

mol y−1 per meter along the margin [46]. This mod-

**10**

[57] inferred gas hydrates to be present in sediments offshore Wilkes Land. A multichannel seismic-reflection survey revealed a reflector showing the characteristics of a BSR [58]: (1) the reflector is at a depth consistent with the pressure/ temperature stability field of gas hydrate, and (2) the reflector shows a reversal of polarity. Unfortunately, a third criterion that the subbottom depth of the reflector increases with increasing depth of water is not met, possibly because of oceanward increasing geothermal gradients as in the case of the inferred gas hydrate off Japan [59]. In addition, other seismic data acquired in 1993 by Japan National Oil Corporation in collaboration with Geological Survey of Japan [60] revealed possible BSRs that could be associated to zones with gas hydrate.

Clearly, additional data are required to confirm and eventually characterize the presence and the distribution of gas hydrate in the Wilkes Land Margin.
