Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns
This paper targets three, diverse audiences: persons calculating ice loads on structures, persons navigating ice-covered waters, and persons using remotely sensed data to estimate ice thickness. The most extensive set of drilling measurements to have been made on thick multi-year ice since the 1980s...
Published in: | Cold Regions Science and Technology |
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Format: | Article in Journal/Newspaper |
Language: | English |
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Elsevier
2018
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Online Access: | https://doi.org/10.1016/j.coldregions.2018.10.016 https://nrc-publications.canada.ca/eng/view/object/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 https://nrc-publications.canada.ca/fra/voir/objet/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 |
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ftnrccanada:oai:cisti-icist.nrc-cnrc.ca:cistinparc:73cf6532-ff66-459d-a990-2de9c27e33a1 2023-05-15T14:29:01+02:00 Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns Johnston, M. E. 2018-11-09 text https://doi.org/10.1016/j.coldregions.2018.10.016 https://nrc-publications.canada.ca/eng/view/object/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 https://nrc-publications.canada.ca/fra/voir/objet/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 eng eng Elsevier issn:0165-232X Cold Regions Science and Technology, Volume: 158, Publication date: 2018-11-09, Pages: 30–51 doi:10.1016/j.coldregions.2018.10.016 multi-year ice thickness freeboard draft deformed ice statistics article 2018 ftnrccanada https://doi.org/10.1016/j.coldregions.2018.10.016 2021-09-01T06:16:51Z This paper targets three, diverse audiences: persons calculating ice loads on structures, persons navigating ice-covered waters, and persons using remotely sensed data to estimate ice thickness. The most extensive set of drilling measurements to have been made on thick multi-year ice since the 1980s is presented based upon 22 floes sampled in some of the most remote regions in the world from years 2007 to 2011. Thickness and freeboard measurements from more than 600 drill-holes indicated that mean thicknesses and standard deviations of floes in Nares Strait, the Canadian Arctic Archipelago (CAA) and the Beaufort Sea ranged from 3.4 ± 1.3 m to 14.7 ± 3.8 m. Approximately 23% of the floes had an average thickness of 10 m or more, making them comparable to the 8 to 12 m thick hummock that caused the highest loads ever measured on the offshore structure Molikpaq. The continued presence of thick multi-year ice shows that, although the modal thickness of thermodynamically grown old ice has decreased, driving forces continue to create deformed multi-year ice. The overall thickness distribution of thermodynamically grown and mechanically deformed multi-year ice is lognormally distributed in all of the examined geographic regions. Probability of exceedance curves were used to address underestimated probabilities in the tail. Assessment of first order autocorrelation coefficients showed that drill hole measurements were statistically independent for ~85% of the 100 to 200 m long transects. Linear regressions of freeboard versus thickness had less predictive skill at the point-scale (R² of 0.57, 10 m spacing) than averages at the transect-scale (R² of 0.78, ~100 m) and floe-scale (R² of 0.88, up to ~1 km). The anomalously high freeboard of some drill holes, transects and floes has a number of plausible explanations including loose ice blocks on the underside of relatively level floes, ice blocks in the keel of deformed floes, elevated blocks on the top surface of relatively level ice without a keel, and/or the low density of the elevated and submerged portions of multi-year ice. Peer reviewed: Yes NRC publication: Yes Article in Journal/Newspaper Arctic Archipelago Arctic Beaufort Sea Canadian Arctic Archipelago Nares strait ice covered waters National Research Council Canada: NRC Publications Archive Arctic Canadian Arctic Archipelago Nares ENVELOPE(158.167,158.167,-81.450,-81.450) Cold Regions Science and Technology 158 30 51 |
institution |
Open Polar |
collection |
National Research Council Canada: NRC Publications Archive |
op_collection_id |
ftnrccanada |
language |
English |
topic |
multi-year ice thickness freeboard draft deformed ice statistics |
spellingShingle |
multi-year ice thickness freeboard draft deformed ice statistics Johnston, M. E. Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
topic_facet |
multi-year ice thickness freeboard draft deformed ice statistics |
description |
This paper targets three, diverse audiences: persons calculating ice loads on structures, persons navigating ice-covered waters, and persons using remotely sensed data to estimate ice thickness. The most extensive set of drilling measurements to have been made on thick multi-year ice since the 1980s is presented based upon 22 floes sampled in some of the most remote regions in the world from years 2007 to 2011. Thickness and freeboard measurements from more than 600 drill-holes indicated that mean thicknesses and standard deviations of floes in Nares Strait, the Canadian Arctic Archipelago (CAA) and the Beaufort Sea ranged from 3.4 ± 1.3 m to 14.7 ± 3.8 m. Approximately 23% of the floes had an average thickness of 10 m or more, making them comparable to the 8 to 12 m thick hummock that caused the highest loads ever measured on the offshore structure Molikpaq. The continued presence of thick multi-year ice shows that, although the modal thickness of thermodynamically grown old ice has decreased, driving forces continue to create deformed multi-year ice. The overall thickness distribution of thermodynamically grown and mechanically deformed multi-year ice is lognormally distributed in all of the examined geographic regions. Probability of exceedance curves were used to address underestimated probabilities in the tail. Assessment of first order autocorrelation coefficients showed that drill hole measurements were statistically independent for ~85% of the 100 to 200 m long transects. Linear regressions of freeboard versus thickness had less predictive skill at the point-scale (R² of 0.57, 10 m spacing) than averages at the transect-scale (R² of 0.78, ~100 m) and floe-scale (R² of 0.88, up to ~1 km). The anomalously high freeboard of some drill holes, transects and floes has a number of plausible explanations including loose ice blocks on the underside of relatively level floes, ice blocks in the keel of deformed floes, elevated blocks on the top surface of relatively level ice without a keel, and/or the low density of the elevated and submerged portions of multi-year ice. Peer reviewed: Yes NRC publication: Yes |
format |
Article in Journal/Newspaper |
author |
Johnston, M. E. |
author_facet |
Johnston, M. E. |
author_sort |
Johnston, M. E. |
title |
Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
title_short |
Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
title_full |
Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
title_fullStr |
Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
title_full_unstemmed |
Thickness and freeboard statistics of Arctic multi-year ice in late summer: three, recent drilling campaigns |
title_sort |
thickness and freeboard statistics of arctic multi-year ice in late summer: three, recent drilling campaigns |
publisher |
Elsevier |
publishDate |
2018 |
url |
https://doi.org/10.1016/j.coldregions.2018.10.016 https://nrc-publications.canada.ca/eng/view/object/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 https://nrc-publications.canada.ca/fra/voir/objet/?id=73cf6532-ff66-459d-a990-2de9c27e33a1 |
long_lat |
ENVELOPE(158.167,158.167,-81.450,-81.450) |
geographic |
Arctic Canadian Arctic Archipelago Nares |
geographic_facet |
Arctic Canadian Arctic Archipelago Nares |
genre |
Arctic Archipelago Arctic Beaufort Sea Canadian Arctic Archipelago Nares strait ice covered waters |
genre_facet |
Arctic Archipelago Arctic Beaufort Sea Canadian Arctic Archipelago Nares strait ice covered waters |
op_relation |
issn:0165-232X Cold Regions Science and Technology, Volume: 158, Publication date: 2018-11-09, Pages: 30–51 doi:10.1016/j.coldregions.2018.10.016 |
op_doi |
https://doi.org/10.1016/j.coldregions.2018.10.016 |
container_title |
Cold Regions Science and Technology |
container_volume |
158 |
container_start_page |
30 |
op_container_end_page |
51 |
_version_ |
1766303117515685888 |