Saturday, August 25, 2018

Antarctica 2.0 - 7

Fig. 1 WOD Zone 3611 in Area B
I. Background

Regular readers are familiar with the Dredd Blog series concerning Antarctica (Antarctica 2.0, 2, 3, 4, 5, 6 [& supplements A, B, C, D, E, F]).

It details tidewater glaciers of Antarctica.

The most recent work in that series was Antarctica 2.0 - 6 [& supplements A, B, C, D, E, F], which listed tidewater glaciers all around Antarctica by ocean area and by WOD Zone.

The gist of the set of posts in the series is that extremely cold water can melt tidewater glaciers so long as that water is less cold ("warmer") than the tidewater glacier it is in contact with.

The paper mentioned in Section II below uses typical language, in that, "warm" is not the warm we usually think of as fuzzy warm:
"warm, modified, circumpolar deep water [p. 7010]" is further defined as "(0∘ C to 0.5∘ C) [p.7011]"
It is the kind of "warm" (32∘ F ... 0∘ C) water where hypothermia and death would take place ... if you stayed in this "warm" water too long (Hypothermia Table).

Nevertheless, such hypothermia causing water temperatures can still melt even colder tidewater glacial ice (Antarctica 2.0 - 5).

II. New Scientific Evidence @ Two Glaciers

A relatively recent paper supports the notion of this Dredd Blog series which argues that Antarctica has been melting for a decade or so longer than commonly believed.

That recent paper was published in Geophysical Research Letters under the title "Mass Loss of Totten and Moscow University Glaciers, East Antarctica, Using Regionally Optimized GRACE Mascons" (PDF).

The two glaciers we are discussing in today's post and in that recent paper "cover a large area, especially Totten glacier (537,900 km2 (Li et al., 2015) versus 221,600 km2 for Moscow University)" (ibid, page 7011).

We constantly hear "West Antarctica" when sea level change is mentioned, but hardly ever "East Antarctica" because of the old "it is gaining mass and is not melting" myth (see Antarctica 2.0).

But as the paper points out:
"There are, however, large drainage sectors in EAIS [East Antarctica Ice Sheet] that exhibit a significant mass loss and hold potential for major sea level rise. In particular, Totten glacier has a sea level rise potential of 3.9 m (Li et al., 2015) versus 3.3 m for the entire marine sector of WAIS [West Antarctica Ice Sheet] (Bamber et al., 2009). Totten is the largest outlet glacier in EAIS (Li et al., 2016; Pritchard et al., 2009) in terms of its grounding line discharge of 71 ± 3 Gt/yr between 2003 and 2008 (Rignot et al., 2013). Li et al. (2016) reported a significant mass loss for this glacier and linked its temporal variability to changes in oceanic forcing from warm ["(+0∘ C to +0.5∘ C)" - p. 7011], modified, circumpolar deep water (mCDW) coming in contact with the glacier."
(ibid, Introduction, p. 7010, emphasis added). In other words, just one of those glaciers studied in the paper (Totten) has more sea level rise potential than all of the West Antarctica Ice Sheet marine glaciers put together.

That paper was authored by Mohajerani, Velicogna, and Rignot then published on line July 25, 2018.

The paper focuses on two glaciers in the Southern Ocean at what Dredd Blog has designated as Area B (nicknamed "East Indian Ocean section").

The entity called "Moscow University Glacier" in the paper is also called Moscow University Ice Shelf on Wikipedia.

In this post I will use author Rignot's description "Moscow University Glacier" because he was a co-author in the paper we are discussing in this post and because he is a recognized authority.

III. Mass Loss Caused By Melt

The seawater temperatures and ice-melt temperatures at various depths of the WOD Zone where Totten Glacier and Moscow Glacier are located are graphed @ Fig. 1 (cf.  Hot, Warm, & Cold Thermal Facts: Tidewater-Glaciers, 2, 3, 4).

Mass loss of ice sheets means mass increase of the oceans, which is a cause for concern:
"Due to the vulnerability of these glaciers to enhanced mCDW intrusion in the future and its potential for considerable sea level rise, it is critical to evaluate, understand, and monitor the mass changes of these glaciers and ice shelves." - p. 7011

"Our results provide reduced uncertainties and higher confidence that the Totten/Moscow sector of EAIS has been losing mass relatively rapidly in the last 15 years." - p. 7018
(ibid, emphasis added). Ah, the old proverbial "worse than previously thought" syndrome, eh?

The next post in this series is here, the previous post in this series is here.

1 comment:

  1. "Big oil asks government to protect its Texas facilities from climate change" (link)