**3. Weddell Sea**

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 Arctic [53].

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 hydrate stability zone.

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.

**11**

Ross Sea (**Figure 8**).

*Gas Hydrates in Antarctica*

**4. Wilkes Land margin**

**5. The Ross Sea**

driven glacial history [23].

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

BSRs that could be associated to zones with gas hydrate.

[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

Clearly, additional data are required to confirm and eventually characterize the

In the last two decades, the Ross Sea Embayment area has been considered a laboratory of growing interest for the reconstruction of the past Antarctic environment, the onset of Antarctic Eocene-Paleocene glaciation, climates studies, the understanding of the tectonic deformation and global sea level changes that all have

The main Ross Sea elongated N-S sedimentary troughs, such as the Victoria Land Basin, the Drigalsky Basin, the northern continuation of the Northern Basin, the Central Basin, the Joides Basin and the Eastern Basin are bounded by basement highs and morphological banks. They were formed during the late Cretaceous major rifting phase and later during the Cenozoic, while a widespread igneous activity

The potential presence of gas hydrate is supported by the identification of hydrocarbons in the Ross Sea area. In fact, in the central and eastern Ross Sea, the cored Miocene muddy sediments at the DSDP sites showed high contents of total hydrocarbon gas (mainly methane; [61]). In the western Ross Sea, analysis of sediments from gravity cores showed the presence of hydrocarbon gases with low concentrations of methane [62] and in the McMurdo Sound, both CIROS-1 and MSSTS-1 wells, detected small amount of organic carbon [63, 64]. Moreover, [65] supposed the presence of a BSR, an indirect indication of the presence of gas hydrate, on a seismic line, located in the Victoria Land Basin. Moreover, in the same part of the Ross Sea, an extensive field of pockmarks at 450–500 m depth and unusual flat-topped seafloor mounds was identified on a detailed multibeam dataset [66, 67]. One hypothesis discussed by the authors is that these features may be carbonate banks because of their proximity to the inferred subsurface gas hydrate, although their preferred interpretation is that the features are of volcanic origin. At this stage, to confirm or refuse the presence of gas hydrate in the Ross Sea more measurements are necessary. Recently, [23] performed a modeling of the base of gas hydrate stability based on the steady-state approach by using literature data, such as bathymetric and well data, sea bottom temperature, a variable geothermal gradient and assuming that the natural gas is methane, in order to identify the areas where the gas hydrate stability is verified The modeling was performed in the whole

The results from the modeling suggested that depth and distribution of the base of the gas hydrate stability zone are correlated with the bathymetry. In fact,

affected the West Antarctic Rift System ([23] and references therein).

presence and the distribution of gas hydrate in the Wilkes Land Margin.
