Oceanography | Vol. 36, No. 1
at 4,200 m depth is bounded by steep rift
valley walls and punctuated by a series
of axial volcanic ridges and smaller vol-
canic mounds (Michael et al., 2003).
Edmonds et al. (2003) inferred the pres-
ence of an active hydrothermal vent site
from chemical data and assigned to a
small (1.5–2 km in diameter) volcanic
mound rising approximately 400 m from
the seafloor, at depths between 4,300 m
and 3,850 m (Figure 1b,c). A dredge from
south to north across this mound recov-
ered components of a sulfide chimney
in addition to abundant pillow basalts.
In parallel, in situ sensor data from a
MAPR (Miniature Autonomous Plume
Recorder) instrument attached to the
dredge revealed evidence for a turbid-
ity anomaly consistent with a nearby
source of active black smoker venting at a
depth of 2,800–3,400 m (Edmonds et al.,
2003; Michael et al., 2003). During the
PS86 AURORA expedition, CTD profil-
ing, coupled with water column chemis-
try, revealed further evidence for ongoing
hydrothermal activity on the Aurora
mound (Boetius, 2015; German et al.,
2022a). Seabed surveys with the Ocean
Floor Observation System (OFOS) deep-
tow camera across the summit from
north to south revealed deep rifts through
the thick sedimented seafloor across the
base of the volcanic mound. This imag-
ing, paired with CTD data, led to the first
imaging of an active black smoker on
Gakkel Ridge at 82°53.83'N, 6°15.32'W,
at ~3,900 m depth, on what was named
the Aurora Vent Field (AVF; Boetius,
2015; German et al., 2022a). The OFOS
surveys showed that the Aurora mound
has steep vertical basalt walls intermixed
with lower angle, sediment-draped steps.
The top of the mound is flat and sediment
covered, and the observed fauna con-
sisted of high abundances of filter feeders,
mostly glass sponges and anemones, and
at least two species of shrimp. Ophiuroids,
swimming polychaetes, and crustaceans
(potentially isopods) were also observed.
At the active vent site, bacterial mats and
small gastropods and amphipods were
observed (Boetius, 2015). The physico-
chemical and microbiological character-
ization of the huge buoyant vent plume
hovering above the AVF showed evidence
for venting fluids enriched in meth-
ane, and possibly hydrogen, fueling high
microbial activity in the plume (German
et al., 2022a; Massimiliano Molari, Max
Planck Institute for Marine Microbiology,
pers. comm., 2022). Due to the lack of a
deep-diving remotely operated vehicle
(ROV), however, no physical samples of
fluids, rocks, microbes, or animals could
be collected from the vent field.
In 2019, the Hot Vents in an Ice-
Covered Ocean (HACON19) cruise on
R/V Kronprins Haakon returned to the
Aurora mound, with the aim of conduct-
ing a multidisciplinary survey of the sea-
floor ecosystems centered around the
coordinates of the black smoker iden-
tified in 2014 by the PS86 Aurora team
(Boetius, 2015). This cruise obtained
new visual data of the AVF with the
towed Ocean Floor Observation and
Bathymetry System (OFOBS; Purser
et al., 2019; German et al., 2022a), con-
firming the presence of at least three black
smokers colonized by sparse fauna com-
posed of mostly gastropods and amphi-
pods (Bünz et al., 2019). In addition, a
wealth of samples on the sedimented sur-
face of the Aurora mound were collected,
Gakkel Ridge
Greenland
Svalbard
FIGURE 1. (a) Map of the Gakkel Ridge in the Central Arctic Ocean with known hydrothermal plume
signals indicated by yellow stars (from Edmond et al., 2003) and the Aurora Vent Field marked with
a red star. (b) A red triangle locates the Aurora Vent Field within the Aurora mound based on pre-
vious bathymetry from the AMORE and AURORA/AWI expeditions. (c) The Aurora Vent Field (red
triangle) is shown against multibeam bathymetry of the Aurora mound based on bathymetry from
the HACON19 and HACON21 expeditions.