Estimation of iceberg draft

Abstract

ABSTRAm P r e v i o u s s t u d i e s t o c o r r e l a t e i c e b e r g d r a f t w i t h i t s above water dimensions are reviewed. Their f i n d i n g s are t e s t e d u s i n g d a t a on measurements of over 200 icebergs. The correlation between the d r a f t and t h e l e n g t h , w i d t h , h e i g h t and mass of each of t h e s e i c e b e r g s i s presented. The anal y s i s i n d i c a t e d t h a t t h e u p p e r limit of iceberg d r a f t is i t s l e n g t h , 1.5 times i t s width, or 10.5 times i t h e i g h t . The lower limit was 0.25 i t s l e n g t h , 0.4 i t s w i d t h , o r i t s h e i g h t . A simple e m p i r i c a l e x p r e s s i o n t o r e l a t e t h e h e i g h t of an i c e b e r g t o i t s d r a f t / h e i g h t r a t i o f o r each type of iceberg was obtained, based on t h e measured d a t a . The e x p e c t e d e r r o r i n v o l v e d i n e s t i m a t i n g i c e b e r g d r a f t u s i n g t h e e m p i r i c a l e x p r e s s i o n s and t h e d e g r e e of c o n f i d e n c e i n t h e e s t i m a t e d v a l u e a r e e v a l u a t e d .

First-Order Estimates of Coastal Bathymetry in Ilulissat and Naajarsuit Fjords, Greenland, from Remotely Sensed Iceberg Observations

“…The much larger difference between the two ratio values in the Upernavik region is likely the result of differences in the calving processes of the source glaciers (Sermeq and Naajarsuit Sermiat), though our value’s similarity to that calculated by Hotzel and Miller [32] suggests it is within the expected range of iceberg depth–width ratios. Among the other studies of Arctic icebergs and their size characteristics (e.g., [34,55]) we were unable to find additional published median depth–width (or height–width) ratios with which to compare our data, though El-Tahan and El-Tahan [55] provided potential upper and lower bounds for establishing a depth–width relationship.…”

Exceptionally Large Icebergs and Ice Islands in Eastern Canadian Waters: A Review of Sightings from 1900 to Present

“…However, an estimate of draft can be obtained if the height is known. Based on published draft-to-height ratios for tabular icebergs (El-Tahan and El-Tahan, 1982;Danish Hydrological Institute, 1979), it is clear that exceptionally long tabular icebergs in the highest height category considered (>40 m high) would represent a low risk for a structure situated in water depths less than 100 m. Conversely, an iceberg or ice island in the lowest height category (< 10 m high) would represent a danger to a fixed structure on all but the shallowest offshore banks. The danger from icebergs in the intermediate height category would vary with the nature of the iceberg and the water depth.…”

Surveying a Floating Iceberg With the USV SEADRAGON

“…Complementary to direct measurements, artificial intelligence algorithms may be developed to predict the "missing" portion based on the survey data. The algorithm would reconstruct the unsurveyed portion based on established iceberg stability conditions and empirical equations, such as the stability theories discussed by EL-Tahan and EL-Tahan (1982). For iceberg deterioration studies, we suggest performing more CTD casts in the downstream in order to quantify the water mass at increased spatial and temporal resolution.…”

“…The above-water shape is normally measured using photogrammetry (Farmer and Robe, 1975). Statistical equations (EL-Tahan and EL-Tahan, 1982;Barker et al, 2004) have been developed to estimate iceberg draft and crosssectional areas based on the above-water characteristics, such as the height, length, and width. However, the lack of available data results in low-confidence in these models compared to direct measurements.…”