Prospects for seasonal forecasting of iceberg distributions in the North Atlantic

Abstract

An efficient approach to ocean-iceberg modelling provides a means for assessing prospects for seasonal forecasting of iceberg distributions in the northwest Atlantic, where icebergs present a hazard to mariners each spring. The stand-alone surface (SAS) module that is part of the Nucleus for European Modelling of the Ocean (NEMO) is coupled with the NEMO iceberg module (ICB) in a "SAS-ICB" configuration with horizontal resolution of 0.25°. Iceberg conditions are investigated for three recent years, 2013-2015, characterized by widely varying iceberg distributions. The relative simplicity of SAS-ICB facilitates efficient investigation of sensitivity to iceberg fluxes and prevailing environmental conditions. SAS-ICB is provided with daily surface ocean analysis fields from the global Forecasting Ocean Assimilation Model (FOAM) of the Met Office. Surface currents, temperatures and height together determine iceberg advection and melting rates. Iceberg drift is further governed by surface winds, which are updated every 3 h. The flux of icebergs from the Greenland ice sheet is determined from engineering control theory and specified as an upstream flux in the vicinity of Davis Strait for January or February. Simulated iceberg distributions are evaluated alongside observations reported and archived by the International Ice Patrol. The best agreement with observations is obtained when variability in both upstream iceberg flux and oceanographic/atmospheric conditions is taken into account. Including interactive icebergs in an ocean-atmosphere model with sufficient seasonal forecast skill, and provided with accurate winter iceberg fluxes, it is concluded Electronic supplementary material The online version of this article (https://doi.org/10.1007/ s11069-017-3136-4) contains supplementary material, which is available to authorized users.

Using Vertically Integrated Ocean Fields to Characterize Greenland Icebergs' Distribution and Lifetime

“…This is important both in permanently covered regions (such as north of Greenland), where keeping icebergs longer leads to increasing iceberg lifetime due to sea ice damping effect on waves, and in seasonally covered regions such as Baffin Bay, where the seasonal freezing and melting of sea ice controls the timing of icebergs that reach the Grand Banks (Marko et al, ). Marsh et al () showed that variations in this timing may cause icebergs to move more onshore or offshoreward. Introducing sea ice locking could, therefore, fix the double‐peak seasonal cycle in VERT and, consequently, change the icebergs' average distance from the coast. Icebergs only slow down in shallow regions instead of being completely grounded.…”

Evidence for iceberg fertilization of the NW Atlantic

“…While ~ 80% of the former's iceberg Fe will be transported in icebergs calving from Greenland (Bigg et al, 1997), most such icebergs will melt, either entirely or in large part, before they enter the Labrador Current. Marsh et al (2018) estimated that only ~ 2.5% of the calved iceberg flux reaches the red box of the main area in Fig. 3.…”

Forecasting the severity of the Newfoundland iceberg season using a control systems model

“…The forecasts could be used as input to ocean-iceberg models, forced by atmospheric forecast fields, to provide forecast iceberg density maps as well as the bulk estimate made here. Indeed, this has already been trialled in a hindcast study (Marsh et al 2017). These various options will be investigated in future work.…”

“…Previous work had suggested that the dominant terms in the WERR model of recent decades had a lag of 8 months or longer (Zhao et al 2016;Marsh et al 2017 1977-2006 up to 1987-2016 to form our ensemble. This allows us to seek the impact of the evolution of the model relationship between I48N and the forcing variables on our prediction.…”