Antarctic iceberg impacts on future Southern Hemisphere climate

Schloesser, Fabian; Friedrich, Tobias; Timmermann, Axel; DeConto, Robert M.; Pollard, David

doi:10.1038/s41558-019-0546-1

Cited by 48 publications

(61 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…There are also structural errors in the CMIP models, notably their coarse resolution, which prevents representation of important processes on the Antarctic continental shelf, and the absence of feedbacks between freshwater released through ice-shelf and iceberg melting and the ocean components of CMIP models. Recent studies suggested that the ocean subsurface may warm by a few tenths of a degree by 2100 in response to large freshwater released by the Antarctic Ice Sheet (Bronselaer et al, 2018;Golledge et al, 2019;Schloesser et al, 2019). There are also more local feedbacks that are not represented in our framework.…”

Section: Discussionmentioning

confidence: 94%

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Jourdain¹,

Asay‐Davis²,

Hattermann³

et al. 2019

Preprint

View full text Add to dashboard Cite

Abstract. Climate model projections have previously been used to compute ice-shelf basal melt rates in ice-sheet models, but the strategies employed – e.g. ocean input, parameterization, calibration technique, and corrections – have varied widely and are often ad-hoc. Here, a methodology is proposed for the calculation of circum-Antarctic basal melt rates for floating ice, based on climate models, that is suitable for ISMIP6, the Ice Sheet Model Intercomparison Project for CMIP6 (6th Coupled Model Intercomparison Project). The past and future evolution of ocean temperature and salinity is derived from a climate model by estimating anomalies with respect to the modern day, which are added to an present-day climatology constructed from existing observational datasets. Temperature and salinity are extrapolated to any position potentially occupied by a simulated ice shelf. A simple formulation is proposed for a basal-melt parameterization in ISMIP6, constrained by the observed temperature climatology, with a quadratic dependency on either the non-local or local thermal forcing. Two calibration methods are proposed: 1) based on the mean Antarctic melt rate (MeanAnt) and 2) based on melt rates near Pine Island's deep grounding line (PIGL). Future Antarctic mean melt rates are an order of magnitude greater in PIGL than in MeanAnt. The PIGL calibration, and the local parameterization, result in more realistic melt rates near grounding lines. PIGL is also more consistent with observations of interannual melt rate variability underneath Pine Island and Dotson ice shelves. This work stresses the need for more physics and less calibration in the parameterizations, and for more observations of hydrographic properties and melt rates at interannual and decadal time scales.

show abstract

Section: Discussionmentioning

confidence: 94%

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Jourdain¹,

Asay‐Davis²,

Hattermann³

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…While variation in ice shelf basal melting is not the only external forcing that can affect the Antarctic ice sheet, the loss of buttressing due to ice shelf thinning from increased basal melting, in particular of deep ice near the grounding line, is thought to be the primary driver of the increased ice discharge (e.g., Pritchard et al, 2012;Gudmundsson, 2013;Seroussi et al, 2014). Other ocean-driven changes, such as calving induced by ocean waves (MacAyeal et al, 2006;Massom et al, 2018), may also influence ice shelf stability, but there is presently little evidence of their impact on long-term variations in the ice sheet mass balance.…”

Section: Approachmentioning

confidence: 99%

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

et al. 2020

View full text Add to dashboard Cite

Abstract. Climate model projections have previously been used to compute ice shelf basal melt rates in ice sheet models, but the strategies employed – e.g., ocean input, parameterization, calibration technique, and corrections – have varied widely and are often ad hoc. Here, a methodology is proposed for the calculation of circum-Antarctic basal melt rates for floating ice, based on climate models, that is suitable for ISMIP6, the Ice Sheet Model Intercomparison Project for CMIP6 (6th Coupled Model Intercomparison Project). The past and future evolution of ocean temperature and salinity is derived from a climate model by estimating anomalies with respect to the modern day, which are added to a present-day climatology constructed from existing observational datasets. Temperature and salinity are extrapolated to any position potentially occupied by a simulated ice shelf. A simple formulation is proposed for a basal melt parameterization in ISMIP6, constrained by the observed temperature climatology, with a quadratic dependency on either the nonlocal or local thermal forcing. Two calibration methods are proposed: (1) based on the mean Antarctic melt rate (MeanAnt) and (2) based on melt rates near Pine Island's deep grounding line (PIGL). Future Antarctic mean melt rates are an order of magnitude greater in PIGL than in MeanAnt. The PIGL calibration and the local parameterization result in more realistic melt rates near grounding lines. PIGL is also more consistent with observations of interannual melt rate variability underneath Pine Island and Dotson ice shelves. This work stresses the need for more physics and less calibration in the parameterizations and for more observations of hydrographic properties and melt rates at interannual and decadal timescales.

show abstract

“…While those findings provide useful insights into likely future changes driven by increased Antarctic melt, the results depend on the assumed future emissions scenario and do not account for meltwater entering the ocean at depth or with a nonuniform spatial distribution, which is likely to impact local sea ice. A study by Schloesser et al (2019) highlights the importance of icebergs to the distribution of meltwater entering the Southern Ocean. An ice sheet model was used to partition Antarctic mass loss between icebergs and meltwater entering the ocean at the coastal ice shelves.…”

Section: Introductionmentioning

confidence: 99%

Climate Response to Increasing Antarctic Iceberg and Ice Shelf Melt

et al. 2020

View full text Add to dashboard Cite

Mass loss from the Antarctic continent is increasing, however climate models either assume a constant mass loss rate, or return snowfall over land to the ocean to maintain equilibrium. Numerous studies have investigated sea ice and ocean sensitivity to this assumption and reached different conclusions, possibly due to different representations of melt fluxes. The coupled atmosphere-land-ocean-sea ice model, HadGEM3-GC3.1, includes a realistic spatial distribution of coastal melt fluxes, a new ice shelf cavity parametrization and explicit representation of icebergs. This makes it appropriate to revisit how increasing melt fluxes influence ocean and sea ice, and to assess whether responses to melt from ice shelves and icebergs are distinguishable. We present results from simulated scenarios of increasing meltwater fluxes and show that these drive sea ice increases and, for increasing ice shelf melt, a decline in Antarctic Bottom Water formation. In our experiments, the mixed layer around the Antarctic coast deepens in response to rising ice shelf meltwater, and shallows in response to stratification driven by iceberg melt. We find similar surface temperature and salinity responses to increasing meltwater fluxes from ice shelves and icebergs, but mid-layer waters warm to greater depths and further north when ice shelf melt is present. We show that as meltwater fluxes increase, snowfall becomes more likely at lower latitudes, and Antarctic Circumpolar Current transport declines. These insights are helpful for interpretation of climate simulations that assume constant mass loss rates, and demonstrate the importance of representing increasing melt rates for both ice shelves and icebergs.

show abstract

Antarctic iceberg impacts on future Southern Hemisphere climate

Cited by 48 publications

References 42 publications

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections

Climate Response to Increasing Antarctic Iceberg and Ice Shelf Melt

Contact Info

Product

Resources

About