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$BBj!!L\!'(BSea Ice Dynamics: Recent Results on Spectra and Scaling
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$B@VF;%1%k%S%sGH$KH<$&@.AX7w!]BPN.7wBg5$8r492aDx$H(B ($BF#86@5CR(B) $BH/I=MW;](B :
$BG.BSBPN.7w3&LLNN0h$OBPN.7wBg5$$,@.AX7w$X91>oE*$KM"Aw$5$l$F$$$kl(B $B=j$G$"$k$H9M$($i$l$F$*$j!"@.AX7w$NBg5$HyNL@.J,G;EY!&J,I[$r5,Dj$7$F$$$k(B $B=EMW$JNN0h$G$"$k!#Nc$($P!"$3$3(B40$BG/$N4V$K@.AX7w$N?e>x5$G;EY$OG/#1!s$N3d(B $B9g$G5^B.$KA}2C$7$F$$$k$3$H$,:G6a9-$/CN$i$l$k$h$&$K$J$j!"$=$l$,%*%>%sAX(B $B2sI|$NCY1d$r$b$?$i$7$F$$$k$3$H$,7|G0$5$l$F$$$k$,!"$=$b$=$bG.BSBPN.7w3&(B $BLLNN0h$K$*$$$F@.AX7w$XF~$k?e>x5$G;EY$,$I$N$h$&$JNO3X2aDx$G7h$^$C$F$$$k(B $B$N$+$K$D$$$F$O!"D9G/5DO@$5$l$F$-$F$$$k$K$b4X$o$i$:L$$@$K7hCe$7$F$$$J$$!#(B $B$3$l$^$G e>:N.$K$h$k0z$->e$2$H!"(B $B@>B@J?MN$+$iEl%$%s%IMN0h$J$ICO0hE*$K8BDj$5$l$F$$$kGX$N9b$$@QMp1@3hF0$K(B $BH<$&2aDx$G$"$C$?$,!"FC$K8e Z5r$r$H$i$($k$3$H$,MF0W$G$J$$$?$a!"(B $B35G0E*D>4QE*8&5f$N0h$r$J$+$J$+=P$k$3$H$,=PMh$F$$$J$$$h$&$KH/I= %s$dJ| \:Y$K8+D>$9$3$H(B $B$K$h$C$F!"BPN.7w3&LL$rLL$G$O$J$/?t(Bkm$B$N8|$_$r;}$C$?AX!&NN0h$H$H$i$($?J}(B $B$,$$$$$N$G$O$J$$$+$H$$$&?7$7$$9M$(J}!J(BTTL$B!a(BTropical Tropopause Layer$B!K(B $B$,?;F)$7$D$D$"$k!#(BTTL$BFb$K$*$1$k=`?eJ?M"Aw$NLr3d$KCeL\$9$k8&5f $l$NF@0U5;$H$=$l$>$l$N;kE@$r;}$C$F(BTTL$B$K$^$D$o(B $B$k5DO@$KD)$s$G$$$k$H$$$C$?>u67$G$"$k!#(B $B;d<+?H$O!"(B1995$BG/$K%s%>%s%G=8Cf4QB,$N7k(B $B2L$+$i!"BPN.7w3&LLNN0h$rEA$o$k@VF;%1%k%S%sGH!"$D$^$jOG@15,LO>qMp$NLr3d(B $B$KCmL\$9$k$h$&$K$J$C$?(B[Fujiwara et al., JGR, 1998]$B!#(BSOWER$B%W%m%8%'%/%H(B $B$K$h$k%,%i%Q%4%9$K$h$k?e>x5$%>%s%G4QB,$N7k2L$+$i$O!"@VF;%1%k%S%sGH$,BP(B $BN.7w3&LLNN0h$r4%Ag2=$5$;$k%a%+%K%:%`$r;}$C$F$$$k$3$H$r8+=P$7(B[Fujiwara et al., GRL, 2001]$B!"Bg5$Bg=[4D%b%G%k$rMQ$$$??tCM qMp$G$"$k$3$H$r3NG'$7!"$=$N3h(B $BF0EY$N5(@a@-!&7PEY0MB8@-$r;XE&$7$?(B[Fujiwara and Takahashi, JGR, 2001]$B!#(B $B:G6a$G$O!"%$%s%I%M%7%"$G2TF/$7;O$a$F$$$k@VF;Bg5$%l!<%@!u$r35(B $B4Q$7!"<+$i$,Ds0F$7$F$-$?OG@15,LO>qMp$NLr3d$rAm3g$7$?>e$G!"?7E7CO$G$"$k(B $B;%KZ$K$*$$$F:#8e$3$N2]Bj$K Sea Ice Dynamics: Recent Results on Spectra and Scaling (Matti Lepparanta) $BH/I=MW;](B :
A brief introduction is given first into the dynamics of sea ice, consisting the description of mechanical state of drift ice, rheology, and the conservation laws of ice and momentum. Recent results are then presented on two themes: scaling of sea ice dynamics and the variance spectra of ice velocity. The momentum equation is analysed for scaling and key non- dimensional quantities. So-called free drift is governed by the roughness ratio of the upper and lower ice surfaces, while for drift in the presence of internal friction the ratio ice strength to external forcing provides a length scale, which classifies the dynamics in different basins. The use of ice tanks to study mechanical properties of drift ice floe fields is discussed with examples shown of uniaxial compression tests. The frequency spectra of sea ice is analysed based on analytical sea ice - ocean boundary layer (OBL) modelling. The principal time scales are the response times of ice and OBL, Coriolis period, and adjustment time of the ice volume. The full two-body problem needs to be solved: an ice-only model gives too weak inertial signal while a locked ice-ocean model puts the general variance level too much down for the ice. The dominant property of internal dynamics is to conserve energy in the feeded frequency since the ice stress is at on/off state for converging/diverging motion but the general sub- linear nature sea ice rheology has an additional tendency to transfer kinetic energy toward lower frequencies.-----
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mail-to:momoko@ees.hokudai.ac.jp / Tel: 011-706-2359