Relating ocean temperatures to frontal ablation rates at Svalbard tidewater glaciers: Insights from glacier proximal datasets

Felicity A Holmes,Jakob Kuttenkeuler,Jari Krützfeldt,Nina Kirchner,Riko Noormets

doi:10.1038/s41598-019-45077-3

Abstract

Fjord-terminating glaciers in Svalbard lose mass through submarine melt and calving (collectively: frontal ablation), and surface melt. With the recently observed Atlantification of water masses in the Barents Sea, warmer waters enter these fjords and may reach glacier fronts, where their role in accelerating frontal ablation remains insufficiently understood. Here, the impact of ocean temperatures on frontal ablation at two glaciers is assessed using time series of water temperature at depth, analysed alongside meteorological and glaciological variables. Ocean temperatures at depth are harvested at distances of 1 km from the calving fronts of the glaciers Kronebreen and Tunabreen, western Svalbard, from 2016 to 2017. We find ocean temperature at depth to control c. 50% of frontal ablation, making it the most important factor. However, its absolute importance is considerably less than found by a 2013–2014 study, where temperatures were sampled much further away from the glaciers. In light of evidence that accelerating levels of global mass loss from marine terminating glaciers are being driven by frontal ablation, our findings illustrate the importance of sampling calving front proximal water masses.

Highlights

The rates of frontal ablation at tidewater glaciers are a key uncertainty in future sea level rise projections[1], but direct observations of calving and submarine melt, two processes collectively referred to as frontal ablation, are difficult to obtain
We present a 376 day time series of water temperature, collected by a LoTUS buoy moored at 67 m water depth in Kongsfjorden, ca 1 km from the calving front of Kronebreen, western Svalbard to assess drivers of frontal ablation between 25 August 2016 and 4 September 2017
Sound velocity profiles (SVP) taken at various calving front proximal sites between 23 and 26 August 2016 show that 55% of observations fall into the Atlantic water (AW) classification range, suggesting a high proportion of warm water in the inner part of Kongsfjorden

Summary

Introduction

The rates of frontal ablation at tidewater glaciers are a key uncertainty in future sea level rise projections[1], but direct observations of calving and submarine melt, two processes collectively referred to as frontal ablation, are difficult to obtain. For sites in Svalbard and Greenland, previous studies have found that ocean temperatures at depth exert a primary control on the frontal ablation rate of marine-terminating glaciers[2,3]. In the wake of the recently observed atlantification of the Arctic Ocean and the Barents Sea[13,14,15] some of Svalbard’s tidewater glaciers have become exposed to increasingly warmer waters at their marine ice fronts[14], rendering them ideal sites for investigating controls on frontal ablation. We present a 376 day time series of water temperature, collected by a LoTUS buoy moored at 67 m water depth in Kongsfjorden, ca 1 km from the calving front of Kronebreen, western Svalbard to assess drivers of frontal ablation between 25 August 2016 and 4 September 2017 (see Fig. 1). Results relating to Kronebreen will be compared to a calculated value for submarine melt

Methods

Results

Discussion

Conclusion