An iceberg drift and decay model to compute the ice-rafted debris and iceberg meltwater flux: Application to the interglacial North Atlantic

An iceberg drift and decay model that computes the long-term ice-rafted debris (IRD) and iceberg meltwater flux over an entire ocean basin is presented. The model requires atmospheric and oceanic flow fields and has three main operations: iceberg drift, decay, and debris release. Using present atmospheric and oceanic flow fields in the North Atlantic, the model is able to reproduce modern iceberg drift paths and seasonal iceberg occurrences. Using the same flow fields, IRD and iceberg meltwater flux to the North Atlantic are computed. Core-top data do not preserve an adequate record of present-day IRD distribution on the ocean floor; thus modeled IRD results are compared with IRD results from marine isotopic stage 5e (the last interglacial), a period most similar to present interglacial conditions. Similarity between the modeled and observed IRD patterns confirms that present ocean surface conditions affecting iceberg drift and decay are similar to those of stage 5e. Detailed comparison reveals icebergs from stage 5e reaching as far east as 20 degrees W, which is not reproduced by the model under existing oceanographic conditions. This discordance suggests that the 5e IRD data set includes deposits from times colder than today, either because of truly colder intervals in 5e or because of dating uncertainties in the data. Modeled meltwater flux to the North Atlantic exhibits large seasonal and spatial variations. Using results from a recent study of North Atlantic Deep Water (NADW) circulation sensitivity to freshwater forcing and assuming a steady Greenland ice volume, iceberg meltwater forcing is insufficient during interglacial conditions to produce even a partial NADW collapse.