Schaffer Amos A.

No Thumbnail Available
Last Name
Schaffer
First Name
Amos A.
ORCID

Filters

2017 - 2020 2
2
2
Reset filters

Settings

Search Results

Now showing 1 - 2 of 2
  • Article
    Ocean circulation and variability beneath Nioghalvfjerdsbrae (79 North Glacier) ice tongue
    (American Geophysical Union, 2020-08-10) Lindeman, Margaret R. ; Straneo, Fiamma ; Wilson, Nathaniel J. ; Toole, John M. ; Krishfield, Richard A. ; Beaird, Nicholas ; Kanzow, Torsten ; Schaffer, Janin
    The floating ice tongue of 79 North Glacier, a major outlet glacier of the Northeast Greenland Ice Stream, has thinned by 30% since 1999. Earlier studies have indicated that long‐term warming of Atlantic Intermediate Water (AIW) is likely driving increased basal melt, causing the observed thinning. Still, limited ocean measurements in 79 North Fjord beneath the ice tongue have made it difficult to test this hypothesis. Here we use data from an Ice Tethered Mooring (ITM) deployed in a rift in the ice tongue from August 2016 to July 2017 to show that the subannual AIW temperature variability is smaller than the observed interannual variability, supporting the conclusion that AIW has warmed over the period of ice tongue thinning. In July 2017, the AIW at 500 m depth in the ice tongue cavity reached a maximum recorded temperature of 1.5°C. Velocity measurements reveal weak tides and a mean overturning circulation, which is likely seasonally enhanced by subglacial runoff discharged at the grounding line. Deep inflow of AIW and shallow export of melt‐modified water persist throughout the record, indicating year‐round basal melting of the ice tongue. Comparison with a mooring outside of the cavity suggests a rapid exchange between the cavity and continental shelf. Warming observed during 2016–2017 is estimated to drive a 33 ± 20% increase in basal melt rate near the ice tongue terminus and a 14 ± 2% increase near the grounding line if sustained.
  • Article
    A-to-I RNA editing in the earliest-diverging Eumetazoan phyla
    (Oxford University Press, 2017-04-08) Porath, Hagit T. ; Schaffer, Amos A. ; Kaniewska, Paulina ; Alon, Shahar ; Eisenberg, Eli ; Rosenthal, Joshua J. C. ; Levanon, Erez ; Levy, Oren
    The highly conserved ADAR enzymes, found in all multicellular metazoans, catalyze the editing of mRNA transcripts by the deamination of adenosines to inosines. This type of editing has two general outcomes: site specific editing, which frequently leads to recoding, and clustered editing, which is usually found in transcribed genomic repeats. Here, for the first time, we looked for both editing of isolated sites and clustered, non-specific sites in a basal metazoan, the coral Acropora millepora during spawning event, in order to reveal its editing pattern. We found that the coral editome resembles the mammalian one: it contains more than 500,000 sites, virtually all of which are clustered in non-coding regions that are enriched for predicted dsRNA structures. RNA editing levels were increased during spawning and increased further still in newly released gametes. This may suggest that editing plays a role in introducing variability in coral gametes.