Changes in the annual sea ice freeze–thaw cycle in the Arctic Ocean from 2001 to 2018
<p>The annual sea ice freeze–thaw cycle plays a crucial role in the Arctic atmosphere—ice–ocean system, regulating the seasonal energy balance of sea ice and the underlying upper-ocean. Previous studies of the sea ice freeze–thaw cycle were often based on limited accessible in situ or easily a...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2022-12-01
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| Series: | The Cryosphere |
| Online Access: | https://tc.copernicus.org/articles/16/4779/2022/tc-16-4779-2022.pdf |
| Summary: | <p>The annual sea ice freeze–thaw cycle plays a crucial role in the
Arctic atmosphere—ice–ocean system, regulating the seasonal energy balance
of sea ice and the underlying upper-ocean. Previous studies of the sea ice
freeze–thaw cycle were often based on limited accessible in situ or easily
available remotely sensed observations of the surface. To better understand
the responses of the sea ice to climate change and its coupling to the upper
ocean, we combine measurements of the ice surface and bottom using
multisource data to investigate the temporal and spatial variations in the
freeze–thaw cycle of Arctic sea ice. Observations by 69 sea ice mass balance
buoys (IMBs) collected from 2001 to 2018 revealed that the average ice basal
melt onset in the Beaufort Gyre occurred on 23 May (<span class="inline-formula">±6</span> d),
approximately 17 d earlier than the surface melt onset. The average ice
basal melt onset in the central Arctic Ocean occurred on 17 June (<span class="inline-formula">±9</span> d), which was comparable with the surface melt onset. This difference was
mainly attributed to the distinct seasonal variations of oceanic heat
available to sea ice melt between the two regions. The overall average onset
of basal ice growth of the pan Arctic Ocean occurred on 14 November (<span class="inline-formula">±21</span> d), lagging approximately 3 months behind the surface freeze
onset. This temporal delay was caused by a combination of cooling the sea
ice, the ocean mixed layer, and the ocean subsurface layer, as well as the
thermal buffering of snow atop the ice. In the Beaufort Gyre region, both
(Lagrangian) IMB observations (2001–2018) and (Eulerian) moored upward-looking sonar (ULS) observations (2003–2018) revealed a trend towards
earlier basal melt onset, mainly linked to the earlier warming of the
surface ocean. A trend towards earlier onset of basal ice growth was also
identified from the IMB observations (multiyear ice), which we attributed to
the overall reduction of ice thickness. In contrast, a trend towards delayed
onset of basal ice growth was identified from the ULS observations, which
was explained by the fact that the ice cover melted almost entirely by the
end of summer in recent years.</p> |
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| ISSN: | 1994-0416 1994-0424 |