Landfast ice thickness in the Canadian Arctic Archipelago from observations and models

Abstract

Abstract. Observed and modelled landfast ice thickness variability and trends spanning more than 5 decades within the Canadian Arctic Archipelago (CAA) are summarized. The observed sites (Cambridge Bay, Resolute, Eureka and Alert) represent some of the Arctic's longest records of landfast ice thickness. Observed end-of-winter (maximum) trends of landfast ice thickness were statistically significant at Cambridge Bay (−4.31 ±1.4 cm decade −1 ), Eureka (−4.65 ±1.7 cm decade −1 ) and Alert (−4.44 ±1.6 cm decade −1 ) but not at Resolute. Over the 50+-year record, the ice thinned by ∼ 0.24-0.26 m at Cambridge Bay, Eureka and Alert with essentially negligible change at Resolute. Although statistically significant warming in spring and fall was present at all sites, only low correlations between temperature and maximum ice thickness were present; snow depth was found to be more strongly associated with the negative ice thickness trends.Comparison with multi-model simulations from Coupled Model Intercomparison project phase 5 (CMIP5), Ocean Reanalysis Intercomparison (ORA-IP) and Pan-Arctic Ice-Ocean Modeling and Assimilation System (PIOMAS) show that although a subset of current generation models have a "reasonable" climatological representation of landfast ice thickness and distribution within the CAA, trends are unrealistic and far exceed observations by up to 2 orders of magnitude. ORA-IP models were found to have positive correlations between temperature and ice thickness over the CAA, a feature that is inconsistent with both observations and coupled models from CMIP5.

Thermodynamic and Dynamic Ice Thickness Changes in the Canadian Arctic Archipelago in NEMO-LIM2 Numerical Simulations

“…Note that neither ANHA4 or ANHA12 has the capability to resolve the difference between YLT and LT1, thus, the same simulated values are shown on the figure for both YLT and LT1. At YLT/LT1, both ANHA4-CGRF (blue line) and ANHA12-CGRF (red line) show similar inter-annual trends to that in GLORYS2v3 (which extends back to 1993, greenline), meaning it is likely a pure initial value problem rather than the model equilibrium issue mentioned in Howell et al (2016). In addition, the seasonal cycle is not clear in the GLORYS2v3 product.…”

“…Landfast ice exists widely in the CAA (Melling, 2002;Galley et al, 2012;Haas and Howell, 2015;Howell et al, 2016). The sea ice model utilized here does produce zero-motion sea ice (e.g., Fig.…”

“…Interpolation is needed to do the comparison between simulated fields and observations. This is also mentioned in Howell et al (2016). To interpolate simulated fields onto the nearest water point (x k , y k ) of each observation site (x obs , y obs ), we utilized a modified inverse distance weighting (IDW) method (eq.…”

“…In addition, the lack of horizontal resolution in these models were also pointed out in Howell et al (2016).…”

“…In this paper, we will focus on the simulated CAA sea ice thickness over recent years (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016), and address the skill of a sea ice model, including but not limited to those mentioned in Howell et al (2016). To be more specific, this paper will discuss 1) the relative importance of thermodynamic and dynamic processes in sea ice growth/melting in simulating the possible 5 variability of sea ice and ocean surface fields in the CAA; 2) high frequency changes in ice growth/melting processes.…”