Ibun abadi: Perbedaan antara revisi

Dalam [[geologi]], '''ibun abadi'''<ref name="KBBI">{{Cite web |url=https://kbbi.kemdikbud.go.id/entri/ibun%20abadi |title=KBBI Daring |author=Badan Pengembangan dan Pembinaan Bahasa |date= |website=KBBI V |publisher=Kementerian Pendidikan dan Kebudayaan Republik Indonesia |access-date=23 Mei 2020}}</ref> ({{lang-en|permafrost}}) adalah lapisan tanah beku yang berada di bawah suhu 0&nbsp;°C selama beberapa tahun. Ibun abadi terbentuk dari es-es yang menggenggam berbagai macam tanah, pasir, dan bebatuan.<ref name="NASAClimateKids">{{Cite web |url=https://climatekids.nasa.gov/permafrost/ |title=What Is Permafrost? |author=Doyle, Heather |date=23 April 2020 |website=NASA Climate Kids |publisher= |access-date=23 Mei 2020}}</ref>

Ibun abadi umumnya terletak di lintang tinggi, yaitu dekat [[Kutub Utara|kutub utara]] dan [[Kutub Selatan|selatan]].<ref name="NRDC">{{Cite web |url=https://www.nrdc.org/stories/permafrost-everything-you-need-know |title=Permafrost: Everything You Need to Know |author=Denchak, Melissa |date=26 Juni 2018 |website=NRDC |publisher= |access-date=23 Mei 2020}}</ref> Ibun abadi biasa terbentuk dalam iklim dengan suhu udara rata-rata tahunan kurang dari titik beku air.

Ibun abadi tidak selalu terbentuk dalam satu lapisan utuh. Ada dua jenis distribusi ibun abadi, yaitu kontinu (sinambung) dan diskontinu (tidak sinambung).<ref name="NationalGeographic">{{Cite web |url=https://www.nationalgeographic.org/encyclopedia/permafrost/ |title=Permafrost - Encyclopedic Entry |author= |date= |website=National Geographic Society |publisher= |access-date=23 Mei 2020}}</ref>

Para ilmuwan memperkirakan bahwa hingga 10²¹ [[Mikroorganisme|mikroba]] berasal dari pencairan es per tahun. Seringkali, mikroba tersebut langsung lepas ke laut. Karena sifat migrasi banyak spesies ikan dan burung, kemungkinan mikroba ini memiliki tingkat transmisi yang tinggi.<ref>{{Cite journal |lastlast1=Smith |firstfirst1=Alvin W. |last2=Skilling |first2=Douglas E. |last3=Castello |first3=John D. |last4=Rogers |first4=Scott O. |date=1 Januari 2004-01-01 |title=Ice as a reservoir for pathogenic human viruses: specifically, caliciviruses, influenza viruses, and enteroviruses|url=http://www.sciencedirect.com/science/article/pii/S0306987704003500 |journal=Medical Hypotheses|language=en |volume=63 |issue=4 |pages=561 |doi=10.1016/j.mehy.2004.05.011 |issn=0306-9877 |language=en |url=http://www.sciencedirect.com/science/article/pii/S0306987704003500 |quote=Both freshwater ice (e.g., glaciers and ice sheets) and sea ice may entrap and preserve enormous numbers of viruses. We estimate that 1017–1021 viable microbes (including fungi, bacteria, and viruses) are released from melting ice annually.}}</ref>

Ibun abadi di timur [[Swiss]] dianalisis oleh para peneliti pada tahun 2016 di situs yang disebut "Muot-da-Barba-Peider". Situs ini memiliki beragam mikroba dengan berbagai bakteri dan kelompok [[eukariota]]. Kelompok bakteri yang menonjol termasuk filum Acidobacteria, [[Actinobacteria]], AD3, [[Bacteroidetes]], [[Chloroflexi]], Gemmatimonadetes, OD1, Nitrospirae, Planctomycetes, [[Proteobacteria]], dan Verrucomicrobia. Jamur eukariotik yang menonjol adalah [[Alveolata]], [[Ascomycota]], [[Basidiomycota]], [[Chlorophyta]] dan [[Zygomycota]]. Pada spesies-spesies tersebut, para ilmuwan mengamati berbagai adaptasi untuk kondisi hidup di bawah suhu nol, termasuk proses metabolisme tereduksi dan [[anaerobik]].<ref>{{Cite journal |lastlast1=Frey |firstfirst1=Beat |last2=Rime |first2=Thomas |last3=Phillips |first3=Marcia |last4=Stierli |first4=Beat |last5=Hajdas |first5=Irka |last6=Widmer |first6=Franco |last7=Hartmann |first7=Martin |date=1 Maret 2016-03-01 |title=Microbial diversity in European alpine permafrost and active layers|url=https://academic.oup.com/femsec/article/92/3/fiw018/2470103 |journal=FEMS Microbiology Ecology|language=en |volume=92 |issue=3 |pages=5 |doi=10.1093/femsec/fiw018 |issn=0168-6496 |url=https://academic.oup.com/femsec/article/92/3/fiw018/2470103 |language=en |quote=The most abundant bacterial groups across all samples included candidate phylum AD3 (20%), Proteobacteria (18%), Verrucomicrobia (13%), Acidobacteria (12%), OD1 (9%), Chloroflexi (7%), Planctomycetes (5%), Actinobacteria (4%), Gemmatimonadetes (4%), Bacteroidetes (2%) and Nitrospirae (1%); all other groups had a relative abundance below 1% (Table 3; Fig. 1c). Only few archaeal sequences (0.5%) were detected in this dataset. The most abundant eukaryotic groups included the fungal phyla Ascomycota (46%), the former Zygomycota (22%) and Basidiomycota (7%), as well as Alveolata (6%) and Chlorophyta (3%).}}</ref>

Wabah [[antraks]] tahun 2016 di [[Semenanjung Yamal]], [[Rusia]], diyakini disebabkan oleh pencairan lapisan es.<ref>{{Cite web|last=Doucleff|first=Michaeleen|date=3 Agustus 2016|title=Anthrax Outbreak In Russia Thought To Be Result Of Thawing Permafrost|url=https://www.npr.org/sections/goatsandsoda/2016/08/03/488400947/anthrax-outbreak-in-russia-thought-to-be-result-of-thawing-permafrost |last=Doucleff |first=Michaeleen |date=3 Agustus 2016 |title=Anthrax Outbreak In Russia Thought To Be Result Of Thawing Permafrost |website=NPR.org |language=en |access-date=31 Desember 2020}}</ref> Di daerah ibun abadi [[Siberia]] secara umum, terdapat dua spesies virus, [[Pithovirus|Pithovirus sibericum]] dan Mollivirus sibericum, yang berusia sekitar 30.000 tahun dan dianggap virus raksasa karena ukurannya lebih besar daripada kebanyakan bakteri dan memiliki genom lebih besar daripada virus lain. Kedua virus tersebut masih bersifat infektif, terlihat dari kemampuannya menginfeksi [[Acanthamoeba]], salah satu genus [[Amoeba (genus)|amuba]].<ref>{{Cite journal |lastlast1=Legendre |firstfirst1=Matthieu |last2=Lartigue |first2=Audrey |last3=Bertaux |first3=Lionel |last4=Jeudy |first4=Sandra |last5=Bartoli |first5=Julia |last6=Lescot |first6=Magali |last7=Alempic |first7=Jean-Marie |last8=Ramus |first8=Claire |last9=Bruley |first9=Christophe| date=2015-09-22 September 2015 |title=In-depth study of Mollivirus sibericum, a new 30,000-y-old giant virus infecting Acanthamoeba|url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4586845/ |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=112 |issue=38 |pages=E5327–E5335 |doi=10.1073/pnas.1510795112 |issn=0027-8424 |pmc=4586845 |pmid=26351664 |url=https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4586845/ |quote=The saga of giant viruses (i.e. visible by light microscopy) started in 2003 with the discovery of Mimivirus. Two additional types of giant viruses infecting Acanthamoeba have been discovered since: the Pandoraviruses (2013) and Pithovirus sibericum (2014), the latter one revived from 30,000-y-old Siberian permafrost. We now describe Mollivirus sibericum, a fourth type of giant virus isolated from the same permafrost sample. These four types of giant virus exhibit different virion structures, sizes (0.6–1.5 µm), genome length (0.6–2.8 Mb), and replication cycles. Their origin and mode of evolution are the subject of conflicting hypotheses. The fact that two different viruses could be easily revived from prehistoric permafrost should be of concern in a context of global warming.}}</ref>

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[[Kategori:Geografi fisik]]