Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland
High spatial resolution CTD profiles and Acoustic Doppler Current Profiler velocity measurements show significant rotational basin-wide, under-ice circulation in May of 2013 and 2014 at Lake Kilpisjärvi, Finland (69°01'N, 20°49'E), a seasonally ice-covered, Arctic lake with negligible thro...
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ftunivbritcolcir:oai:circle.library.ubc.ca:2429/52683 2023-05-15T15:04:50+02:00 Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland Graves, Kelly Elise 2015 http://hdl.handle.net/2429/52683 eng eng University of British Columbia Attribution-NonCommercial-NoDerivs 2.5 Canada http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ CC-BY-NC-ND Text Thesis/Dissertation 2015 ftunivbritcolcir 2019-10-15T18:16:30Z High spatial resolution CTD profiles and Acoustic Doppler Current Profiler velocity measurements show significant rotational basin-wide, under-ice circulation in May of 2013 and 2014 at Lake Kilpisjärvi, Finland (69°01'N, 20°49'E), a seasonally ice-covered, Arctic lake with negligible through-flow. In 2013, a high-pressure horizontal density anomaly with vertically paired rotating circulations was observed. The estimated maximum cyclonic and anti-cyclonic azimuthal velocities magnitudes were 0.03 and 0.02 m s-¹. The Rossby radius (Rri), horizontal length scale at which rotational effects become as important as pressure effects, was estimated to be ∼ 160 m and the Rossby number(R⃘⃘⃘⃘⃘ ), the ratio of the centripetal acceleration to the Coriolis acceleration, ∼ 0.2. It is hypothesized that this circulation was driven by heat flux at the shorelines from warm incoming streams causing a density flow down the slopes to the centre of the lake where the flow converged. This flow was balanced with a shoreward flow beneath the ice. These flows were modified by the earth's rotation, which resulted in the rotational circulation observed. In 2014, a cyclonic, low-pressure horizontal density anomaly was observed near the centre of the lake and was vertically paired with a weak anti-cyclonic anomaly in the top 10 m (mean depth of the lake is 19.5 m). The estimated azimuthal velocities had maximum cyclonic and anti-cyclonic magnitudes of 0.006 and 0.003 m s-¹. The anomaly was estimated to have Rri ∼ 240 m, with R⃘⃘ ∼ 0.12. It is hypothesized that this circulation was driven by sediment release of heat to the overlying water causing a tilt in the isopycnals near the shores of the lake that caused an inward pressure force that was balanced by the Coriolis force and, to a lesser extent, the centripetal acceleration force. The 2013 observations were made immediately prior to ice-off, and the 2014 observations were 12 days prior to ice-off. This time difference allowed for significantly different ice and snow conditions, and the addition of warm inflows, which forced the circulation closer to the ice-off date. These observations add to the growing understanding of the relationship between thermal distribution and circulation under ice. Applied Science, Faculty of Civil Engineering, Department of Graduate Thesis Arctic Kilpisjärvi University of British Columbia: cIRcle - UBC's Information Repository Arctic Arctic Lake ENVELOPE(-130.826,-130.826,57.231,57.231) Kilpisjärvi ENVELOPE(20.767,20.767,69.034,69.034) |
institution |
Open Polar |
collection |
University of British Columbia: cIRcle - UBC's Information Repository |
op_collection_id |
ftunivbritcolcir |
language |
English |
description |
High spatial resolution CTD profiles and Acoustic Doppler Current Profiler velocity measurements show significant rotational basin-wide, under-ice circulation in May of 2013 and 2014 at Lake Kilpisjärvi, Finland (69°01'N, 20°49'E), a seasonally ice-covered, Arctic lake with negligible through-flow. In 2013, a high-pressure horizontal density anomaly with vertically paired rotating circulations was observed. The estimated maximum cyclonic and anti-cyclonic azimuthal velocities magnitudes were 0.03 and 0.02 m s-¹. The Rossby radius (Rri), horizontal length scale at which rotational effects become as important as pressure effects, was estimated to be ∼ 160 m and the Rossby number(R⃘⃘⃘⃘⃘ ), the ratio of the centripetal acceleration to the Coriolis acceleration, ∼ 0.2. It is hypothesized that this circulation was driven by heat flux at the shorelines from warm incoming streams causing a density flow down the slopes to the centre of the lake where the flow converged. This flow was balanced with a shoreward flow beneath the ice. These flows were modified by the earth's rotation, which resulted in the rotational circulation observed. In 2014, a cyclonic, low-pressure horizontal density anomaly was observed near the centre of the lake and was vertically paired with a weak anti-cyclonic anomaly in the top 10 m (mean depth of the lake is 19.5 m). The estimated azimuthal velocities had maximum cyclonic and anti-cyclonic magnitudes of 0.006 and 0.003 m s-¹. The anomaly was estimated to have Rri ∼ 240 m, with R⃘⃘ ∼ 0.12. It is hypothesized that this circulation was driven by sediment release of heat to the overlying water causing a tilt in the isopycnals near the shores of the lake that caused an inward pressure force that was balanced by the Coriolis force and, to a lesser extent, the centripetal acceleration force. The 2013 observations were made immediately prior to ice-off, and the 2014 observations were 12 days prior to ice-off. This time difference allowed for significantly different ice and snow conditions, and the addition of warm inflows, which forced the circulation closer to the ice-off date. These observations add to the growing understanding of the relationship between thermal distribution and circulation under ice. Applied Science, Faculty of Civil Engineering, Department of Graduate |
format |
Thesis |
author |
Graves, Kelly Elise |
spellingShingle |
Graves, Kelly Elise Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
author_facet |
Graves, Kelly Elise |
author_sort |
Graves, Kelly Elise |
title |
Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
title_short |
Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
title_full |
Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
title_fullStr |
Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
title_full_unstemmed |
Under-ice circulation in an Arctic lake : observations from two field seasons in Lake Kilpisjärvi, Finland |
title_sort |
under-ice circulation in an arctic lake : observations from two field seasons in lake kilpisjärvi, finland |
publisher |
University of British Columbia |
publishDate |
2015 |
url |
http://hdl.handle.net/2429/52683 |
long_lat |
ENVELOPE(-130.826,-130.826,57.231,57.231) ENVELOPE(20.767,20.767,69.034,69.034) |
geographic |
Arctic Arctic Lake Kilpisjärvi |
geographic_facet |
Arctic Arctic Lake Kilpisjärvi |
genre |
Arctic Kilpisjärvi |
genre_facet |
Arctic Kilpisjärvi |
op_rights |
Attribution-NonCommercial-NoDerivs 2.5 Canada http://creativecommons.org/licenses/by-nc-nd/2.5/ca/ |
op_rightsnorm |
CC-BY-NC-ND |
_version_ |
1766336563879346176 |