{"id":430,"date":"2015-10-12T19:38:17","date_gmt":"2015-10-12T16:38:17","guid":{"rendered":"http:\/\/we.kybi\/wp\/?page_id=430"},"modified":"2015-10-12T19:38:17","modified_gmt":"2015-10-12T16:38:17","slug":"spatial-planning-of-shipping-and-offshore-activities-in-the-baltic-sea-using-lagrangian-trajectories","status":"publish","type":"page","link":"https:\/\/wavelab.taltech.ee\/?page_id=430","title":{"rendered":"Spatial Planning of Shipping and Offshore Activities in the Baltic Sea Using Lagrangian Trajectories"},"content":{"rendered":"

This abstract has also been accepted to ICS 2011<\/strong> conference.<\/p>\n

 <\/p>\n

Authors: Bert Viikm\u00e4e, <\/strong>Tarmo Soomere, <\/strong>Nicole Delpeche-Ellmann<\/strong><\/p>\n

 <\/p>\n

Oil transportation as one of the largest threats to the Baltic Sea has drastically increased over the last 15\u00a0years. The drift of oil spills is influenced by wind stress, waves, and currents. The properties of transport by\u00a0wind and waves are relatively well known, but the prediction of current-induced transport is more challenging.\u00a0The existence of quasi-persistent patterns of currents in various parts of the Baltic Sea and the presence of\u00a0rapid pathways of the current-driven transport opens a new way towards a technology that uses the marine\u00a0dynamics for the reduction of environmental risks stemming from shipping and offshore and coastal\u00a0engineering activities. The key benefit of this particular technology is an increase in the time during which an\u00a0adverse impact (for example an oil spill) reaches the coastal zone. The idea is to identify areas (of reduced\u00a0risk), which are statistically safer to travel to in terms of the probability of the transport of accidental pollution\u00a0to the vulnerable areas.\u00a0The coastal areas usually have the largest ecological value, thus in this study we consider the nearshore as a\u00a0generic example of a valuable area. While the probability of coastal pollution for most of the open ocean\u00a0coasts can be reduced by shifting ship routes to a larger distance from the coast, the problem for narrow bays,\u00a0like the Gulf of Finland, is how to minimize the probability of hitting either of the opposite coasts.<\/p>\n

The first\u00a0order solution to this problem is the equiprobability line, the probability of propagation of pollution from which\u00a0to either of the coasts is equal. The safe fairway would either follow the equiprobability line or cross an area of\u00a0reduced risk.\u00a0Owing to extreme complexity and high variability of the instantaneous patterns of current fields, we use a\u00a0large number of single simulations in order to estimate the pathways of current-induced drift patterns. The\u00a0propagation of pollution is calculated with the use of the Lagrangian trajectory model TRACMASS (Do\u0308o\u0308s, 1995;\u00a0de Vries and D\u00f6\u00f6s, 2001) that uses pre-computed Eulerian velocities calculated by the Rossby Centre global\u00a0circulation model (Regional Ocean model, RCO, Meier, 2001) with a horizontal resolution of 2\u00d72 nautical miles\u00a0and 41 vertical levels.\u00a0The trajectories of pollution (particle) propagation are calculated based on a linear interpolation of the velocity\u00a0field in each point of grid cells. The position of the trajectories is updated every six hours. Trajectories of\u00a0particles are simulated for a few weeks and saved for further analysis. Simulations with the same initial\u00a0positions of particles are restarted from another time instant and the process is repeated over a chosen time\u00a0period 1987-1992.<\/p>\n

Two methods are used for numerical estimation of the spatial distribution of the probability of hitting the\u00a0opposite coasts. Firstly, four particles (Ni = 4, 1 \u2264 i \u2264 N) are placed in each grid cell. If three or all four\u00a0particles reach the nearshore of a particular coast, the cell is assumed the value of c = \u00b1 1 depending on\u00a0which coast was hit. If no more than two tracers reached a coast within the time period, the cell is assumed\u00a0the value c = 0. Secondly, we used another method, involving a certain local smoothing, by dividing the sea\u00a0area into clusters of 3\u00d73 cells and placing one particle in each cell. By tracing nine trajectories in each cluster\u00a0it is established whether or not the majority of the trajectories end up at one of the coasts. The basic idea is\u00a0the same as above; only the values of (Ni = 9, 1 \u2264 i \u2264 N) and the initial positions of the tracer with respect to\u00a0the centres of the grid cells are different.\u00a0Both methods produced qualitatively similar probability maps for coastal hits that show substantial seasonal\u00a0and also certain inter-annual variability. A highly interesting feature of the resulting distributions is that some\u00a0open sea regions contain a clear probability gradient while some other regions of basically the same size\u00a0exhibit extensive areas with very low (and essentially constant) probability of hitting either of the coasts. In the\u00a0former areas it is possible to clearly define the equiprobability line whereas the latter areas can be identified\u00a0as areas of reduced risk. The distance between different estimates for the location of the equiprobability line\u00a0serves as an implicit measure of uncertainty related with this sort of solution. We demonstrate the location of\u00a0the equiprobability line and areas of reduced risk for the Gulf of Finland and the northern Baltic Proper.\u00a0An alternative method for identification of the equiprobability line and the areas of reduced risk consists in\u00a0constructing spatial maps of time necessary for the current-induced transport of adverse impacts to the\u00a0coastal zone. We also provide the analysis of most frequently hit coastal areas from pollution sources occurring\u00a0along the equiprobability line.<\/p>\n

The presented results confirm that it is possible to considerably reduce the probability coastal pollution by\u00a0adverse impacts released from ships by means of optimising the fairways. The relatively small difference in the\u00a0location of the optimum fairways obtained by different methods indicates a reasonable level of uncertainty\u00a0connected with this type of solution. A highly interesting side result is the discovery of substantially different\u00a0regions in the underlying spatial distributions of the probability of coastal hits. This feature probably reflects\u00a0certain intrinsic difference in the dynamics of sea currents and the corresponding pollution transport between\u00a0different sea areas.<\/p>\n

Bibliography:<\/h3>\n

Andrejev, O., Myrberg, K., Alenius, P. and Lundberg, P. A., Mean circulation and water exchange in the Gulf of\u00a0Finland – a study based on three-dimensional modelling, Boreal Env. Res. 9(1), 1-16 2004<\/p>\n

Soomere, T. and Quak, E, On the potential of reducing coastal pollution by a proper choice of the fairway, J.\u00a0Coast. Res., Special Issue 50, 678-682 2007<\/p>\n

Soomere, T., Viikm\u00e4e, B., Delpeche, N., Myrberg, K., Towards identification of areas of reduced risk in the Gulf\u00a0of Finland, Proceedings of the Estonian Academy of Sciences, 59 (2), 156\u2013165 2010<\/p>\n","protected":false},"excerpt":{"rendered":"

This abstract has also been accepted to ICS 2011 conference.   Authors: Bert Viikm\u00e4e, Tarmo Soomere, Nicole Delpeche-Ellmann   Oil transportation as one of the largest threats to the Baltic Sea has drastically increased over the last 15\u00a0years. The drift of oil spills is influenced by wind stress, waves, and currents. The properties of transport by\u00a0wind and waves are relatively …<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-430","page","type-page","status-publish","hentry","archive-loop-container"],"_links":{"self":[{"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=\/wp\/v2\/pages\/430","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=430"}],"version-history":[{"count":0,"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=\/wp\/v2\/pages\/430\/revisions"}],"wp:attachment":[{"href":"https:\/\/wavelab.taltech.ee\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=430"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}