Answer: The release of methane from thawed permafrost
Explanation:
With increasing global warming, permafrost in the arctic is melting. The carbon and methyl clathrates present in permafrost escape into the atmosphere to form carbon dioxide and methane, both greenhouse gases.
In the Arctic, molecules of methane are trapped in ice crystals as methyl clathrates. When the temperature increases, these crystals release methyl clathrates which become methane when in contact with the atmosphere.
The cause of the increasing atmospheric 
is due to the the thawing of dead organisms present in the permafrost. As the permafrost melts, these organisms decay and release into the atmosphere.
Some meteorites contain organic compounds which may be precursors to today's living cells,<span> provides evidence to support this idea.</span>
The feelings of the indigenous people tend to vary a lot about this topic.
Some of the indigenous people are very hostile to any foreigners in their land, so they would not hesitate to attack, and even in some cases kill.
There are some that feel it as an usurpation of their daily lives, and do not see the tourists very fondly, but are not making any real problems, just avoiding contact.
And there are some indigenous people that actually saw a nice opportunity to modernize and make a profit of the tourists, so they are using their survival skills in the wild in their advantage, and they are very welcoming towards the tourists and encourage them to come.
By siltation, as part of the bed load
