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LONG DISTANCE POLLEN TRANSPORT TO SOUTHERN GREENLAND: IS THERE A REGULAR PATTERN?

ROUSSEAU, DENIS-DIDIER  Université Montpellier II.
Schevin, Patrick  Université Montpellier II.
Duzer, Danielle  Université Montpellier II.
Jolly, Dominique  Université Montpellier II.
Cambon, Genevieve  Université Montpellier II.

The on going EPILOBE project, monitoring the pollen transport to the Greenland coast, is based on several stations where filters are trapping all year long the pollen grains present in the air. A previous record of long distance pollen transport to southern Greenland, at Narsarsuaq, have been observed in 2002 through the capture of pollen grains from trees, hickory and hemlock, oak, beech, hornbeam, walnut, growing in North America. This transport was in agreement with the dates of pollen production measured in southern Canada in the Toronto area, at the northern range of the common distribution of these trees (Fig. 1). The pattern of the transport had been described by using the HYSPLIT application from NOAA, which allows determining backward trajectories.

A new transport to Narsarsuaq has been observed in the filters exposed in Narsarsuaq at about the same timing than in 2003. The filters exposed during weeks 21 (20 - 26 May) and 22 (27 May - 2 June) indicate the occurrence in the Greenland air of pollen grains from trees, which again are better growing in eastern North America (Fig. 2). Despite the plants already observed in 2002, which absolutely indicate North America as a potential source of the pollen, other trees, also growing in eastern North America have been noticed. These are poplar, yew, ash, plane tree, and spruce. The backward air trajectories, computed by the HYSPLIT application for the concerned weeks, show mostly a similar pattern for most of the transport over the Great Lakes area.

Conversely, the total number of pollen grains present in the atmosphere in southern Greenland (total number per cubic meter of air, computed with the available Danish Meteorological Institute) was higher in 2002 than in 2003. It appears then that a regular pattern of air masses responsible for the transport of pollen grains from North America to Greenland should be constant, as already described for anthropogenic pollutants.

REFERENCES
Rousseau, D.D., D. Duzer, G. Cambon, D. Jolly, U. Poulzen, J. Ferrier, P. Schevin, and R. Gros, Long distance transport of pollen to Greenland, Geophysical Research Letters, 30 (14), 1766, 2003.

Rousseau, D.D., D. Duzer, J.L. Etienne, G. Cambon, D. Jolly, J. Ferrier, and P. Schevin, Pollen record of rapidly changing air trajectories to the North Pole, Journal of Geophysical Research, 109 (in press), 2004.



Figure 1. Figure 1. Long distance transport to Narsarsuaq in 2002 (from Rousseau et al. 2002 modified)

A) Backward trajectories provided by the HYSPLIT model [HYSPLIT4Model, 1997] of air masses reaching Narsarsuaq (61.15° N, 45.43° W, 1 m asl) at different altitudes: ground level (red), 1000 m (blue) and 3000 m (green) on June 4th of 2002.The grey area in eastern USA and south-eastern Canada represents the zone where "exoctic" trees are all growing [from Thompson et al., 1999a; Thompson et al., 1999b]. The ?3000m? air mass passed over this area. L: London, P: Peterborough, S: Sudbury, T: Toronto.

B) Altitude variation of the three air masses used in the backward trajectories analysis. The "3000 m" air mass over Narsarsuaq on June 4th, 2002, was at a lower elevation on June 1st, when it passed over the area where "exoctic" trees are growing.


Figure 2. Figure 2. Long distance transport to Narsarsuaq in 2003.

A) Backward trajectories provided by the HYSPLIT model [HYSPLIT4Model, 1997] of air masses reaching Narsarsuaq (61.15° N, 45.43° W, 1 m asl) at different altitudes: ground level (red), 1000 m (blue) and 3000 m (green) on May 20th of 2003.The grey area in eastern USA and south-eastern Canada represents the zone where "exoctic" trees are all growing [from Thompson et al., 1999a; Thompson et al., 1999b].

B) Altitude variation of the three air masses used in the backward trajectories analysis. The "3000 m" air mass over Narsarsuaq on may 20th, 2003, was at a lower elevation on May 14 to 16st, when it passed over the area where the "exoctic" trees are growing.


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