Impact of sea ice floe size distribution on seasonal fragmentation and melt of Arctic sea ice
<p>Recent years have seen a rapid reduction in the summer Arctic sea ice extent. To both understand this trend and project the future evolution of the summer Arctic sea ice, a better understanding of the physical processes that drive the seasonal loss of sea ice is required. The marginal ice z...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2020-02-01
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| Series: | The Cryosphere |
| Online Access: | https://www.the-cryosphere.net/14/403/2020/tc-14-403-2020.pdf |
| Summary: | <p>Recent years have seen a rapid reduction in the summer
Arctic sea ice extent. To both understand this trend and project the future
evolution of the summer Arctic sea ice, a better understanding of the
physical processes that drive the seasonal loss of sea ice is required. The
marginal ice zone, here defined as regions with between 15 % and 80 % sea
ice cover, is the region separating pack ice from the open ocean. Accurate
modelling of this region is important to understand the dominant mechanisms
involved in seasonal sea ice loss. Evolution of the marginal ice zone is
determined by complex interactions between the atmosphere, sea ice, ocean,
and ocean surface waves. Therefore, this region presents a significant
modelling challenge. Sea ice floes span a range of sizes but sea ice models
within climate models assume they adopt a constant size. Floe size
influences the lateral melt rate of sea ice and momentum transfer between
atmosphere, sea ice, and ocean, all important processes within the marginal
ice zone. In this study, the floe size distribution is represented as a
power law defined by an upper floe size cut-off, lower floe size cut-off,
and power-law exponent. This distribution is also defined by a new tracer
that varies in response to lateral melting, wave-induced break-up, freezing
conditions, and advection. This distribution is implemented within a sea ice
model coupled to a prognostic ocean mixed-layer model. We present results to
show that the use of a power-law floe size distribution has a spatially and
temporally dependent impact on the sea ice, in particular increasing the
role of the marginal ice zone in seasonal sea ice loss. This feature is
important in correcting existing biases within sea ice models. In addition,
we show a much stronger model sensitivity to floe size distribution
parameters than other parameters used to calculate lateral melt, justifying
the focus on floe size distribution in model development. We also find that
the attenuation rate of waves propagating under the sea ice cover modulates
the impact of wave break-up on the floe size distribution. It is finally
concluded that the model approach presented here is a flexible tool for
assessing the importance of a floe size distribution in the evolution of sea
ice and is a useful stepping stone for future development of floe size
modelling.</p> |
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| ISSN: | 1994-0416 1994-0424 |