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第288回 大気海洋物理学・気候力学セミナー のおしらせ

日　時： 10月 20日(木) 9:30 - 12:00
Date ： Thu., 20 Oct. 9:30−12:00　　
場　所： 低温科学研究所　2階　講義室 (215)　
Place ： ILTS 2F lecture room (Room No. 215)　

発表者： アンドレアス・プルーサー（外国人特別研究員/低温研）
Speaker:Andreas Preuser （JSPS fellow /ILTS)
題名：Pan-Arctic polynya and salt flux dynamics between 2002/2003 and 2010/2011 - a multi-sensor intercomparison project

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Pan-Arctic polynya and salt flux dynamics between 2002/2003 and 2010/2011 
- a multi-sensor intercomparison project　
（アンドレアス・プルーサー、Andreas Preuser） 



発表要旨: 
An accurate knowledge of wintertime sea-ice production in Arctic polynyas is of vital interest 
for the understanding of atmosphere ? ice ? ocean interactions and the evaluation of climate 
and ocean models. In the framework of a JSPS-funded research stay at the Institute of Low 
Temperature Science (Hokkaido University), a high-resolution (~2km) MODIS thermal infrared 
satellite data set featuring spatial and temporal characteristics of 17 prominent coastal polynya 
regions over the entire Arctic basin (Preuser et al., 2016) is directly compared to a similar data 
set based on AMSR-E passive microwave data (Iwamoto et al., 2014) for the period 2002/2003 
to 2010/2011. 
While the MODIS data set is based on a 1D energy balance model, where thin-ice thicknesses 
up to 20cm are directly derived from ice-surface temperature swath data and ERA-Interim 
atmospheric reanalysis data on a daily basis, the AMSR-E data set is based on an empirical approach 
that utilizes a distinct polarization ratio (PR) ? thin-ice thickness relationship. 
In both data sets, the daily pan-Arctic mapping of thin-ice thicknesses allows for the derivation 
of polynya area and potential thermodynamic ice production. 
Contrary to earlier expectations, the difference in polynya area and ice production estimates is 
smaller when using equal reference areas and time-frames, and for certain regions it showed 
that the passive microwave numbers even exceed their MODIS derived equivalents in 
several years (Fig.1). 
We see that discrepancies between both data sets originate primarily from sensor-specific 
differences in the acquired signal (e.g. open water detection), varying spatial resolutions 
(2km vs. 6.25km) of the used data sets and a varying influence of cloud cover. 
Hence, a possible bias between both data sets mainly depends on the distribution of thin ice 
within the footprint of AMSR-E, potential land spillover effects and the performance of the 
applied cloud-cover correction scheme (Spatial Feature Reconstruction ? SFR) in the MODIS data set. 
In wintertime, the formation of new sea ice in polynyas provides feedback to the underlying ocean 
through brine rejection, i.e. increased salt fluxes into the water column. 
A new panArctic estimation of salt-fluxes based on high resolution MODIS ice production estimates 
will be presented, thereby providing enhanced spatial detail of salt flux dynamics in the Arctic shelf 
seas for the period 2002/2003 to 2014/2015. 

Iwamoto, K.; Ohshima, K.I.; Tamura, T. (2014): Improved mapping of sea ice production in the 
Arctic Ocean using AMSR-E thin ice thickness algorithm. 
Journal of Geophysical Research: Oceans, 119, 3574?3594, doi: 10.1002/2013JC009749. 
Preuser, A., Heinemann, G., Willmes, S., and Paul, S. (2016): Circumpolar polynya regions and 
ice production in the Arctic: Results from MODIS thermal infrared imagery for 2002/2003 to 
2014/2015 with a regional focus on the Laptev Sea, The Cryosphere Discuss., 
doi:10.5194/tc-2016-133, in review

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