Validation and production of RADARSAT‐1 derived ice‐motion maps in the North Water (NOW) polynya, January ‐ December 1998

Abstract

Monitoring ice motion may provide insight into the atmospheric and oceanic forces acting on ice motion and thus the mechanisms that contribute to polynya dynamics. A study of ice kinematics in the North Water (NOW) region was performed using time sequential and spatially overlapping RADARSAT-1 ScanSAR Wide images (January to December 1998) processed by the Canadian Ice Service (CIS) Ice Tracking Algorithm (Tracker). The objectives of this research were to: 1) validate the NOW region ice motions derived using Tracker; 2) create monthly image-maps that present ice speeds and directions over the NOW region for an entire year (January to December 1998); 3) compare these results to previous ice motion studies done in the NOW region; and 4) develop initial insights into relations between derived ice motion and latent and sensible heat mechanisms in the NOW Polynya. Tracker ice motions were validated using in situ ice beacons deployed between April and November 1998. Tracker magnitude and direction coefficients of determination (R 2 ) were 0.93 and 0.79 respectively, with standard errors of estimate of 3.6 km in magnitude and 38.8° in direction. The monthly ice motion maps describe the annual evolution of the polynya quite accurately and compare well to other studies. High levels of ice export are found which supports the theory that winds or ocean currents continually remove ice from the polynya as it forms. A northward import of ice into the polynya along the Greenland coast shows the recycling of ice into the polynya. Evidence of oceanic (sensible) heat contributing to the open water of the polynya was not evident using the Tracker ice motion methods. RÉSUMÉ [Traduit par la rédaction] La surveillance du mouvement des glaces peut donner un aperçu des forces atmosphériques et océaniques qui déterminent le mouvement des glaces et donc des mécanismes qui participent à la dynamique de la polynie. Une étude de la dynamique des glaces a été réalisée dans la région de la polynie des eaux du Nord à l'aide d'une séquence temporelle d'images qui se chevauchent dans l'espace. Ces images, de type ScanSAR Large, ont été produites de janvier à décembre 1998 par RADARSAT-1 et traitées par l'algorithme de poursuite des glaces (Tracker) du Centre canadien des glaces (CCG). L'étude avait pour objectifs : 1) de valider le mouvement des glaces dérivé par le Tracker dans la région de la polynie des eaux du Nord; 2) de créer des cartes-images mensuelles des vitesses et des directions des glaces dans cette région pour toute l'année (de janvier à décembre 1998); 3) de comparer ces résultats aux études précédentes sur le mouvement des glaces faites dans la région; et 4) de donner une première idée des relations qui existent entre le mouvement dérivé des glaces et les mécanismes de chaleur latente et sensible dans la polynie des eaux du Nord. Les mouvements des glaces donnés par le Tracker ont été validés par des balises à glace déployées sur place entre avril et novembre 1998. Les coefficients de détermination (R 2 ) de la grandeur et de la...

Preferential sinking export of biogenic silica during the spring and summer in the North Water Polynya (northern Baffin Bay): Temperature or biological control?

“…The Polynya starts to open toward the south in early spring and reaches its maximum extent in July, before its southern boundary disappears. Ice cover distribution in the NOW during the spring and summer of 1998 (during this study) is described by Mundy and Barber [2001] and Wilson et al [2001], and nutrient distributions are presented by Tremblay et al [2002a]. In addition, Sea‐viewing Wide Field‐of‐view Sensor (SeaWIFS) data analyses for 1998–2000 show that intense spring blooms taking place in May or early June are a recurring feature in the Polynya [ Bélanger , 2001].…”

The formation and maintenance of the North Water Polynya

“…The ice velocity field in northern Baffin Bay forms a cyclonic gyre, primarily driven by wind stress. There are some indications of a cylconic gyre in ice drift maps from synthetic aperture radar imagery (Wilson et al, 2001). The coastline of north-west Greenland interrupts the gyre.…”

Baffin Bay ice drift and export: 2002–2007

“…Strong northerly winds create the conditions necessary to maintain this polynya where newly-formed ice is swept southward under the combined effects of wind and currents. In one study of the ice motion in the NOW region, Wilson et al [2001] report that large areas of sea ice originate from the polynya. However, we are not aware of any quantitative estimates of its winter ice area production in the published literature.…”