Study On Isopycnal Cabbeling Convection In Greenland Sea Produced By Water Masses Of Arctic Ocean

In Greenland sea, the convection produced by isopycnal cabbeling is animportant type of convection. But there is no direct and especial estimate to theintensity of the isopycnal cabbeling convection in Greenland Sea at present. To estimatethe intense of cabbeling convection, August data of HydroBase grid data of monthlymean of temperature and salinity is used to calculate the cabbeling velocity in GINsea on four neutral surfaces. Average cabbeling velocity of GIN sea through direct andsimple calculation is about8.7×10^-6m/s, and spatially varies a lot, especially inhorizontal plane in which the difference is108times. Buoyancy frequency andpotential temperature by interpolation is discontiguous and unsmooth, which leads tothe huge horizontal difference. Results for the statistic show that, on each surface,2%maximal velocity contributes to30%of flux. The average vertical velocity is6.47×10^-6m/s if the2%maximal velocity is limited. This means that the sparse pointswith maximal velocity have a great influence on the estimation of the cabbeling flux.The average velocity of1.19×10^-7m/s is got though three order polynomialfitting of potential temperature and removing singular value of buoyancy frequency,which is two magnitude smaller than the directly calculated one. This velocity havethe same magnitude to that in the low and middle latitude area of north Atlantic Ocean,and is2.5times bigger than it. The result also shows that cabbeling velocity of surfacelayer and deep layer is lager than the middle layer, which means that middle layer ofocean have the smallest cabbeling velocity. That is to say, there are two main mixingcircumstances in which cabbeling may contribute significantly to vertical advection inGIN sea, through isopycnal mixing across strong near-surface and through epineutralmixing of different water masses in the deep ocean. This is also proved by thecalculation though limitation of2%maximal velocity. As small scale mixing processesgreatly contribute to the cabbeling convection, and the polynomial fitting of potentialtemperature will neglect some small scale processes, so this cabbeling velocity is underestimated. The cabbeling velocity of10^-710^-6m/s is supported by this paper. Butattention is required that, it is also just a conservative estimation.The above calculations all support that cabbeling convection produced by ArcticOcean water have larger velocity than the average cabbeling velocity in GIN sea,which is an important vertical circulation.As in Greenland Sea, Recirculating Atlantic Water and water masses from ArcticOcean are the main water masses that involved in the cabbeling convection. TheArctic Ocean is experiencing intense and rapid changes, in which the changes ofwater masses and circulation system will alter isopycnal cabbeling convection ofGreenland Sea, and further affect the global climate system. So this paper thendiscusses the possible effects of various water masses in different regions of ArcticOcean to Greenland Sea cabbeling convection. In this paper, Effective CabbelingConvection Velocity is defined, which is1.73m/d. The rang of salinity and potentialtemperature of masses which could make Effective Cabbeling Convevtion throughmixing with Recirculating Atlantic Water is obtained. In Greenland sea, various watermasses involved in the isopycnal cabbeling convection all originate from AtlanticOcean. Some of them are Recirculating Atlantic Water recirculating in Greenland Sea,the others are Atlantic Water of Arctic which experience recirculating and diving inArctic Ocean. If the later water masses stay in the Arctic Ocean longer, thetemperature gradient will be greater, and the convection will be intenser. While, thewater masses from Pacific Ocean which cross the Arctic Ocean could not be involvedin isopycnal cabbeling convection for its low density. In the Arctic Mediterranean,deep-water temperature varies between the different basins, so these deep watermasses may produce Effective Cabbeling Convection through mixing with GreenlandSea Deep Water. But in the deep and bottom layer of ocean, the current velocity is low,turbulent mixing is weak and temperature gradiant is small, so at present it’s not surewhether the deep convection exists. Through this study, we obtain a qualitativeknowledge of the possible effects of various water masses in Arctic Ocean toGreenland Sea isopycnal cabbeling convection.