Grounding line retreat of Pope, Smith, and Kohler Glaciers, West Antarctica, measured with Sentinel-1a radar interferometry data

We employ Sentinel-1a C band satellite radar interferometry data in Terrain Observation with Progressive Scans mode to map the grounding line and ice velocity of Pope, Smith, and Kohler glaciers, in West Antarctica, for the years 2014–2016 and compare the results with those obtained using Earth Remote Sensing Satellites (ERS-1/2) in 1992, 1996, and 2011. We observe an ongoing, rapid grounding line retreat of Smith at 2 km/yr (40 km since 1996), an 11 km retreat of Pope (0.5 km/yr), and a 2 km readvance of Kohler since 2011. The variability in glacier retreat is consistent with the distribution of basal slopes, i.e., fast along retrograde beds and slow along prograde beds. We find that several pinning points holding Dotson and Crosson ice shelves disappeared since 1996 due to ice shelf thinning, which signal the ongoing weakening of these ice shelves. Overall, the results indicate that ice shelf and glacier retreat in this sector remain unabated

Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9g€¯mm to global mean sea level, with the rate of mass loss rising from 105g€¯Gtg€¯yr-1 between 1992 and 1996 to 372g€¯Gtg€¯yr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9g€¯Gtg€¯yr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86g€¯Gtg€¯yr-1 in 2017 to 444g€¯Gtg€¯yr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9g€¯Gtg€¯yr-1) and, to a lesser extent, from the Antarctic Peninsula (13±5g€¯Gtg€¯yr-1). East Antarctica remains close to a state of balance, with a small gain of 3±15g€¯Gtg€¯yr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)

Mass balance of the Greenland Ice Sheet from 1992 to 2018

In recent decades, the Greenland Ice Sheet has been a major contributor to global sea-level rise1,2, and it is expected to be so in the future3. Although increases in glacier flow4–6 and surface melting7–9 have been driven by oceanic10–12 and atmospheric13,14 warming, the degree and trajectory of today’s imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet’s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. Although the ice sheet was close to a state of balance in the 1990s, annual losses have risen since then, peaking at 335 ± 62 billion tonnes per year in 2011. In all, Greenland lost 3,800 ± 339 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.6 ± 0.9 millimetres. Using three regional climate models, we show that reduced surface mass balance has driven 1,971 ± 555 billion tonnes (52%) of the ice loss owing to increased meltwater runoff. The remaining 1,827 ± 538 billion tonnes (48%) of ice loss was due to increased glacier discharge, which rose from 41 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. Between 2013 and 2017, the total rate of ice loss slowed to 217 ± 32 billion tonnes per year, on average, as atmospheric circulation favoured cooler conditions15 and as ocean temperatures fell at the terminus of Jakobshavn Isbræ16. Cumulative ice losses from Greenland as a whole have been close to the IPCC’s predicted rates for their high-end climate warming scenario17, which forecast an additional 50 to 120 millimetres of global sea-level rise by 2100 when compared to their central estimate

West Antarctic Ice Sheet retreat in the Amundsen Sea driven by decadal oceanic variability

Mass loss from the Amundsen Sea sector of the West Antarctic Ice Sheet has increased in recent decades, suggestive of sustained ocean forcing or an ongoing, possibly unstable, response to a past climate anomaly. Lengthening satellite records appear to be incompatible with either process, however, revealing both periodic hiatuses in acceleration and intermittent episodes of thinning. Here we use ocean temperature, salinity, dissolved-oxygen and current measurements taken from 2000 to 2016 near the Dotson Ice Shelf to determine temporal changes in net basal melting. A decadal cycle dominates the ocean record, with melt changing by a factor of about four between cool and warm extremes via a nonlinear relationship with ocean temperature. A warm phase that peaked around 2009 coincided with ice-shelf thinning and retreat of the grounding line, which re-advanced during a post-2011 cool phase. These observations demonstrate how discontinuous ice retreat is linked with ocean variability, and that the strength and timing of decadal extremes is more influential than changes in the longer-term mean state. The nonlinear response of melting to temperature change heightens the sensitivity of Amundsen Sea ice shelves to such variability, possibly explaining the vulnerability of the ice sheet in that sector, where subsurface ocean temperatures are relatively high

Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9g€¯mm to global mean sea level, with the rate of mass loss rising from 105g€¯Gtg€¯yr-1 between 1992 and 1996 to 372g€¯Gtg€¯yr-1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9g€¯Gtg€¯yr-1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86g€¯Gtg€¯yr-1 in 2017 to 444g€¯Gtg€¯yr-1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9g€¯Gtg€¯yr-1) and, to a lesser extent, from the Antarctic Peninsula (13±5g€¯Gtg€¯yr-1). East Antarctica remains close to a state of balance, with a small gain of 3±15g€¯Gtg€¯yr-1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at 10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)

Mass balance of the Greenland and Antarctic ice sheets from 1992 to 2020

Ice losses from the Greenland and Antarctic ice sheets have accelerated since the 1990s, accounting for a significant increase in the global mean sea level. Here, we present a new 29-year record of ice sheet mass balance from 1992 to 2020 from the Ice Sheet Mass Balance Inter-comparison Exercise (IMBIE). We compare and combine 50 independent estimates of ice sheet mass balance derived from satellite observations of temporal changes in ice sheet flow, in ice sheet volume, and in Earth's gravity field. Between 1992 and 2020, the ice sheets contributed 21.0±1.9 mm to global mean sea level, with the rate of mass loss rising from 105 Gt yr−1 between 1992 and 1996 to 372 Gt yr−1 between 2016 and 2020. In Greenland, the rate of mass loss is 169±9 Gt yr−1 between 1992 and 2020, but there are large inter-annual variations in mass balance, with mass loss ranging from 86 Gt yr−1 in 2017 to 444 Gt yr−1 in 2019 due to large variability in surface mass balance. In Antarctica, ice losses continue to be dominated by mass loss from West Antarctica (82±9 Gt yr−1) and, to a lesser extent, from the Antarctic Peninsula (13±5 Gt yr−1). East Antarctica remains close to a state of balance, with a small gain of 3±15 Gt yr−1, but is the most uncertain component of Antarctica's mass balance. The dataset is publicly available at https://doi.org/10.5285/77B64C55-7166-4A06-9DEF-2E400398E452 (IMBIE Team, 2021)

Beitrag zur Kenntnis westpaläarktischer Bienen der Gattung Andrena (Hymenoptera: Apidae: Andreninae)

Scheuchl, E. (2010): Beitrag zur Kenntnis westpaläarktischer Bienen der Gattung Andrena (Hymenoptera: Apidae: Andreninae). Linzer biologische Beiträge 42 (2): 1445-1455, DOI: http://doi.org/10.5281/zenodo.532396

Andrena (Ulandrena) armeniaca POPOV 1940

Andrena (Ulandrena) armeniaca POPOV 1940 B e s c h r e i b u n g (neu für die Wissenschaft): Körperlänge: 17-19 mm. Färbung: Körper schwarz, Clypeus mit Ausnahme zweier schwarzer Basalmakeln und Nebengesicht weissgelb, unterer Aussenrand der Augen mit weissgelblichem Fleck. Fühler einschliesslich Schaft rot gefärbt, Oberseite mehr oder weniger verdunkelt. Sämtliche Beine mit Ausnahme der Trochanter rotgelb gefärbt, Coxen und Schenkelbasis mehr oder weniger verdunkelt. Tergite 2 und 3 mehr oder weniger ausgedehnt rot gefärbt. Behaarung: Kopf weiss, Scheitel weisslich graubraun behaart. Mesonotum relativ kurz und abstehend, Scutellumrand und Postscutellum länger weisslich graubraun behaart. Tergite überall dicht und kurz weisslichbraun behaart, Tergite 1-5 mit vollständiger dichter Binde. Struktur: K o p f: Clypeus glatt, äusserst dicht, längs der Mitte sehr dicht punktiert. Seitenocellen mindestens 3 Ocellendurchmesser vom Scheitelrand entfernt. – T h o r a x: Mesonotum glatt und glänzend, sehr dicht punktiert. Mittelfeld grob gerunzelt. Nervulus interstitiell bis schwach postfurcal. – A b d o m e n: Tergite glänzend, sehr dicht punktiert. Valven in der Seitenansicht allmählich in die Spitze übergehend. D i f f e r e n t i a l d i a g n o s e A. armeniaca sieht A. fedtschenkoi zum Verwechseln ähnlich; das Weibchen unterscheidet sich neben der etwas grösseren Körperlänge in erster Linie durch das deutlich gerunzelte Mittelfeld, das bei A. fedtschenkoi homogen fein körnig skulptiert ist (vgl. POPOV 1940, GUSENLEITNER & SCHWARZ 2001). Weitere Unterscheidungsmerkmale sind der in Frontalansicht etwas breitere Scheitel und der bogig ausgerandete Labrumanhang bei A. armeniaca. Körperlänge und Skulptur des Mittelfelds können auch beim Männchen zur Unterscheidung herangezogen werden, am auffallendsten sind jedoch die Unterschiede im Genitalbau und in der Form von Sternit 8: Bei A. armeniaca ist der Apex von Sternit 8 halbkreisförmig abgerundet, bei A. fedtschenkoi hingegen ist er deutlich eingekerbt ("fischschwanzförmig". Die Penisvalven sind bei A. armeniaca ähnlich wie bei A. elegans stark blasig vergrössert (gehen jedoch in Seitenansicht allmählich in die Spitze über, während sie bei A. elegans vor der Spitze erweitert sind), bei A. fedtschenkoi sind sie schmal, die Oberseite ist rinnig vertieft, die in dieser Rinne liegende Valvenöffnung ist von einer ebenfalls rinnenförmig geformten Lamelle umschlossen. Bei A. armeniaca besitzen die Gonocoxen einen zahnähnlichen Dorsallobus und die Gonostylusschaufeln sind sehr schmal, bei A. fedtschenkoi fehlt der Dorsallobus und die Gonostylusschaufeln sind breit (siehe dazu Abb. 7 a-e, 8a-d, 9a-d). Weitere Trennungsmerkmale sind der Abstand zwischen Seitenocellus und Scheitelrand (A. armeniaca: ca. 3 Ocellendurchmesser, A. fedtschenkoi: ca. 4 Ocellendurchmesser) und die Schläfenbreite (A. armeniaca: deutlich schmäler als die Augenbreite, A. fedtschenkoi: so breit wie die Augen). Durch die vergleichbare Körpergrösse, die Behaarung und die Färbung des Integuments, insbesondere die ausgedehnte Rotfärbung der Fühler und der Beine gleicht A. armeniaca auf den ersten Blick am meisten der A. fedtschenkoi, der Bau der Genitalien und des Sternits 8 stellt sie jedoch verwandtschaftlich in unmittelbare Nähe der A. elegans; bei dieser sind die Penisvalven in Seitenansicht aber vor der Spitze erweitert, während sie bei A. armeniaca allmählich in die Spitze übergehen. Darüber hinaus unterscheidet sich A. elegans von A. armeniaca durch die schwarz gefärbten Schenkel und Tibien, den fehlenden gelben Fleck am unteren Augenrand und die ausgedehnt schwarz gefärbten Fühler (Scapus und Geisseloberseite schwarz). U n t e r s u c h t e s M a t e r i a l:1, 3 " Türkei, 20 km E Tatvan, 1750 m, 10. Juli 1984, leg. A.W. Ebmer".Published as part of Scheuchl, E., 2010, Beitrag zur Kenntnis westpaläarktischer Bienen der Gattung Andrena (Hymenoptera: Apidae: Andreninae), pp. 1445-1455 in Linzer biologische Beiträge 42 (2) on pages 1453-1454, DOI: 10.5281/zenodo.532396

Andrena (Margandrena) elsei nov.sp., eine neue türkische Sandbienenart (Hymenoptera, Apidae, Andreninae)

Scheuchl, E., Gusenleitner, F. (2009): Andrena (Margandrena) elsei nov.sp., eine neue türkische Sandbienenart (Hymenoptera, Apidae, Andreninae). Linzer biologische Beiträge 41 (1): 947-962, DOI: 10.5281/zenodo.527633