Day 4

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Paper title Fresh Water fluxes from Iceberg (
Authors
  1. Jean Tournadre Ifremer Speaker
Form of presentation Poster
Topics
  • A8. Ocean
    • A8.07 Oceanographic Change of the Arctic Ocean From Space
Abstract text Basal melting of floating ice shelves and iceberg calving constitute the two almost equal paths of freshwater flux (FWF) between the Antarctic ice cap and the Southern Ocean. For the Greenland ice cap the figure are quite similar even if surface melting plays a more significant role.
Basal meltwater and surface melt water are distributed over the upper few hundred meters of the coastal water column while icebergs drift and melt farther away from land.
While the northern hemisphere icebergs are, except for rare exception small (less than10km2), In the southern ocean large icebergs (larger than 100km2) act as a reservoir to transport ice far away from the Antarctic coast into the ocean interior, while fragmentation acts as a diffusive process. It generates plumes of small icebergs that melt far more efficiently than larger ones.
OGCM that include iceberg show that basal ice-shelf and iceberg melting have different effects on the ocean circulation and that icebergs induce significant changes in the modeled ocean circulation and sea-ice conditions around Antarctica or in the northern Atlantic. The transport of ice away from the coast by icebergs and the associated FWF cause these changes. These results highlight the important role plaid by icebergs and their associated FWF play in the climate system. However, there is actually no direct reliable estimate of the iceberg FWF to either validate or constrain the models.
Since 2008 the ALTIBERG project maintains a small iceberg (less than 10km2) database (North and South) using a detection method based on the analysis of satellite altimeter waveforms (http://cersat.ifremer.fr/data/products/catalogue). The archive of positions, areas, dates of icebergs as well as the monthly mean volume of ice icebergs covers now the 1992-present period.
Using classical iceberg's motion and thermodynamics equations constrained by AVISO currents, ODYSEA SST's and Wave Watch 3 wave heights, the trajectories and melting of all detected ALTIBERG icebergs are computed. The results are used to compute the daily FWF.
The FWF's temporal and spatial distribution from 1993 to 2019 are presented as well as the estimation method. The north Atlantic FWF, which has also been estimated, will also be analyzed.
Figure 1 presents the mean daily FWF, the mean daily volume of ice as well as the mean surface and thickness of the icebergs for the 1993-2019 period on a 50x50km grid.