The Greenland and Antarctic ice sheets under 1.5 °C global warming (Pattyn et al, 2018)

Flashcards about the Greenland and Antarctic ice sheets under 1.5°C global warming based on lecture notes

What is primarily hampering projections of future sea-level rise (SLR)?

Incomplete knowledge of the contributions of the Greenland and the Antarctic ice sheets (GrIS and AIS)

What is ice-sheet mass balance defined as?

The net result of all mass gains and losses

What is surface mass balance (SMB) defined as?

The net mass balance at the ice-sheet surface, including the firn layer. It does not include dynamical mass loss associated with ice flow or melting at the ice–ocean interface.

What accounts for about one-third of the recent GrIS mass loss?

Increased ice flow

What accounts for all of the recent mass loss in Antarctica?

Increased ice flow

How much has Greenland warmed since the mid-1990s?

∼5 °C in winter and ∼2 °C in summer

What is the mean SLR equivalent from the GrIS for 2012–2016?

0.65–0.73 mm yr−1

What drove the current observed SMB decrease from 2000 to 2012?

Increased melt and subsequent runoff

What atmospheric circulation changes are observed in summer since the 2000s over the GrIS?

A negative North Atlantic Oscillation (NAO) and a concurrent positive phase of the East Atlantic Pattern

How does a decrease in SMB impact the ice-sheet surface?

Lowers the ice-sheet surface, which in turn lowers SMB because at lower elevations, near-surface air temperature is generally higher.

What range of ice-sheet volume change is reported by modelling studies of the GrIS, according to RCP2.6, by 2100?

14–78 mm s.l.e.

What two interrelated feedback mechanisms exist as part of the coupled ice sheet–atmospheric system in the long term?

The SMB–elevation feedback and the melt–albedo feedback

What range of regional summer temperature threshold leading to GrIS decline?

1.1–2.3 °C above pre-industrial, with a best estimate of 1.8 °C

When did the AIS start losing mass?

Since the mid-1990s

What is the average contribution of the AIS to SLR between 1992 and 2017?

0.15–0.46 mm yr−1 s.l.e.

Where does major ice loss from the AIS stem from?

An increased discharge of grounded ice into the ocean

What role do ice shelves play in major ice loss from the AIS?

The buttressing provided by ice shelves can affect inland ice hundreds of kilometres away, and hence controls grounding-line retreat and associated ice flow acceleration.

What is the major limiting factor in projecting the future AIS response?

How global warming relates to ocean dynamics that bring CDW onto and across the continental shelf, potentially increasing sub-shelf melt.

What is MISI?

Marine Ice Sheet Instability; thinning and eventual flotation of the ice near the grounding line, which moves the latter into deeper water where the ice is thicker leading to increased ice flux.

What is MICI?

Marine Ice Cliff Instability; rapid disintegration of ice shelves due to hydrofracturing leading to an acceleration of ice discharge in Antarctica.