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

Abstract

Icebergs represent approximately half of Greenland's yearly mass loss, having important implications for biological productivity, freshwater fluxes in the ocean, and navigation. This study applies an iceberg model that uses integrated ocean fields (from surface to iceberg keel) to simulate the drift and decay of Greenland icebergs. This version of iceberg model (VERT) is compared with a more widely adopted version (SURF) which only uses surface ocean fields in its equations. We show that icebergs in VERT tend to drift along the shelf break, while in SURF they concentrate along the coastline. Additionally, we show that Greenland's southeast coast is the source of ∼60% of the icebergs that cross the interior of the Labrador Sea-a region that stages buoyancy-driven convection and is, therefore, sensitive to freshwater input.Plain Language Summary Thousands of icebergs break off from Greenland every year, threatening navigation along North America's east coast. Since it is difficult to monitor individual icebergs, computer simulations are useful to help us understand their common pathways and, potentially, to predict when and from where icebergs come from. In this study, we use an improved iceberg model (one that uses the variations of ocean currents and temperature with depth to interact with icebergs) to simulate Greenland icebergs' distribution and their persistence in different regions of the North Atlantic. We show that this improved version better reproduces iceberg pathways observed in the past. Moreover, we find that icebergs breaking off from the southeast part of Greenland compose most icebergs reaching the middle of the Labrador Sea-a region where iceberg melt may affect ocean circulation and, consequently, heat distribution from tropics to poles. This means that an increasing volume of icebergs coming out of this particular region in a warmer world might have an effect back on the climate.

Seasonality of Freshwater in the East Greenland Current System From 2014 to 2016

“…Several regions where freshwater deviates into the interior have been identified downstream of our array in observations: the tip of CF (Holliday et al, ) and the unstable West Greenland Current (Bracco et al, ; Myers et al, ; Rykova et al, ; Schmidt & Send, ). Furthermore, several recent modeling studies have found that freshwater originating east of Greenland is more likely to enter the Labrador Sea than freshwater originating west of Greenland (Gillard et al, ; Luo et al, ; Marson et al, ; Tesdal et al, ; Wang et al, ). In particular, water over the slope east of Greenland is more likely to enter the Labrador Sea than water originating on the shelf (Schulze Chretien & Frajka‐Williams, ).…”

“…Freshwater is a key player in the formation of globally significant water masses in the subpolar gyre (Manabe & Stouffer, 1995). In particular, the freshwater flowing east of Greenland, which includes Arctic freshwater and sea ice, as well as Greenland melt and icebergs, has been shown to be the primary source of freshwater for the subpolar gyre interior in recent modeling studies (Gillard et al, 2016;Luo et al, 2016;Marson et al, 2018;Schulze Chretien & Frajka-Williams, 2018;Tesdal et al, 2018;Wang et al, 2018). Freshwater export from the Arctic and Greenland is expected to increase (Alley et al, 2005;Wang & Overland, 2009), with potential consequences for the formation of intermediate North Atlantic Deep Waters and global climate.…”

Drivers for Atlantic-origin waters abutting Greenland

“…Additionally, the study 20 only looked at the impact from the freshwater flux of the GrIS. The inclusion of an iceberg model coupled with an ocean model may give further insight to the heat and freshwater budget in regions of high GrIS discharge, such as explained in Marson et al (2018). Values here correspond to the percentage out of all particles and grid cells that virtual particles can be found in a given grid cell.…”

The Aftermath of Petermann Glacier Calving Events (2008–2012): Ice Island Size Distributions and Meltwater Dispersal

“…The strength of the Atlantic Meridional Overturning Circulation (AMOC) is of concern when considering the increasing freshwater flux from the Greenland Ice Sheet and potential consequences to global ocean circulation and energy transfers (Bamber et al, 2012;Böning et al, 2016;Gillard et al, 2016;Yang et al, 2016). In their modeling studies, Gillard et al (2016), Marson et al (2018), and Wagner and Eisenman (2017) note that direct meltwater input from the Greenland Ice Sheet or via iceberg deterioration could affect deep-water convection in the North Atlantic and potentially lead to a slowdown of the AMOC. However, a sustained freshwater flux anomaly of at least 7 mSv in the North Atlantic is thought to be necessary to substantially slowdown the AMOC (Brunnabrend et al, 2015;Yang et al, 2016).…”