March 2023 | Oceanography
A SHORT HISTORY OF GAKKEL
RIDGE EXPLORATION
Forty-five years after the discovery
of hydrothermal vents (Corliss et al.,
1979), research into these unique hab-
itats and their rich submarine ecosys-
tems has brought about revolutionary
findings in biology, chemistry, and geo-
physics. Understanding how these dis-
tinctive ecosystems are supported by
sunlight- independent microbial primary
productivity based on chemosynthesis
changed the way we understand life on
Earth (Van Dover et al., 2018). They have
inspired our understanding of the ori-
gin of life on Earth (Martin et al., 2008)
and are now influencing the choice of
exploration targets aimed at the discov-
ery of extraterrestrial life in our solar
system (Hand and German, 2018; Hand
et al., 2020). The exotic faunal commu-
nities at active hydrothermal vents are
also of high interest given their physio-
logical adaptations and the high degree
of endemicity, and for their potential in
providing marine genetic resources of
use in biomedicine, cosmetics, and bio-
fuels, among others (Van Dover et al.,
2018). In addition, interest in the poten-
tial for mineral resources in hydrother-
mal vent deposits has greatly increased
in the last two decades, and exploration
licenses for such resources have been
granted for national and international
waters (Jones et al., 2020).
Since the discovery of deep-sea hydro-
thermal vents in 1977, just over 30% of the
global mid-ocean ridge system has been
investigated (Beaulieu et al., 2015). To
date, exploration has yielded an inventory
of 722 confirmed high-temperature vent
sites, with a further 720 high- temperature
vents inferred from water column data,
as reported in the InterRidge Vents
Database in September 2022 (Beaulieu
and Szafranski, 2020). There may be hun-
dreds of additional active hydrothermal
systems and their associated faunal com-
munities yet to be discovered worldwide
along the unexplored branches and sec-
tions of the global mid-ocean ridge sys-
tem, particularly along the least explored
slow and ultra-slow spreading ridges
(Beaulieu et al., 2015).
Current data on vent communities
globally has identified 11 biogeographic
provinces, but their delineation is still
being debated (Rogers et al., 2012). Until
now, the vent faunal communities of the
ice-covered Gakkel Ridge in the Central
Arctic Ocean remained unexplored
because of their remote and climatologi-
cally challenging location. This study puts
the Aurora Vent Field of the Gakkel Ridge
on the global map of chemosynthetic-
based ecosystems, providing an initial
overview of the vent field and the eco-
system it supports.
The Gakkel Ridge (Figure 1a) extends
1,800 km from the northern end of the
Lena Trough off Northeast Greenland
(81°N) to near the Siberian shelf at
87°N. It was initially predicted to host
an extremely low number of active sites
based on the assumption that hydrother-
mal flux scaled directly with spreading
rate (E.T. Baker et al., 1996). This hypoth-
esis was revisited after exploration of the
Southwest Indian Ridge showed that even
ultra-slow spreading ridges could host
abundant submarine venting (German
et al., 1998). Technological and method-
ological challenges of working at great
depth in regions of permanent sea ice
cover have constrained the exploration
of the Gakkel Ridge. In 2001, Edmonds
et al. (2003) obtained first evidence of
hydrothermal venting on nine to twelve
discrete locations along the Gakkel Ridge
during the InterRidge two-icebreaker
(R/V Polarstern and USCGC Healy)
Arctic Mid-Ocean Ridge Expedition
(AMORE; Figure 1a). Continued explo-
ration during the Arctic Gakkel Vents
(AGAVE) expedition in 2007 provided
evidence of explosive volcanism at 85°N
and demonstrated that large-scale pyro-
clastic activity is possible along even the
deepest portions of the global mid-ocean
ridge volcanic system (Sohn et al., 2008).
Seismic studies suggest substantial mag-
matic activity, serpentinization, and fluid
flow at this slowest of all Earth’s ridge sys-
tems (Michael et al., 2003; Schlindwein
and Schmid, 2016). Between 2002 and
2010, the ChEss program aimed to
improve understanding of the global bio-
geography of chemosynthetic-based eco-
systems (M.C. Baker et al., 2010). Based
on the increasing evidence of hydro-
thermal venting along the Gakkel Ridge,
the ChEss program identified a num-
ber of poorly investigated regions where
research efforts should focus. The Gakkel
Ridge was recognized as one of the miss-
ing pieces of the global biogeographic
puzzle (Ramirez-Llodra et al., 2007).
Building on the results of the AMORE
2001 expedition (Edmonds et al., 2003),
in 2014, R/V Polarstern expedition PS86
AURORA aimed to study geophysical,
geological, geochemical, and biological
processes at hydrothermal vents on the
Gakkel Ridge, with a focus on the southern
segment (Boetius, 2015). In this region,
the spreading rate is 14.5–13.5 mm yr–1,
(slightly faster than the average rate for
the overall ridge), and the ridge axis floor
ABSTRACT. Evidence of hydrothermal venting on the ultra-slow spreading Gakkel
Ridge in the Central Arctic Ocean has been available since 2001, with first visual evi-
dence of black smokers on the Aurora Vent Field obtained in 2014. But it was not until
2021 that the first ever remotely operated vehicle (ROV) dives to hydrothermal vents
under permanent ice cover in the Arctic were conducted, enabling the collection of
vent fluids, rocks, microbes, and fauna. In this paper, we present the methods employed
for deep-sea ROV operations under drifting ice. We also provide the first description
of the Aurora Vent Field, which includes three actively venting black smokers and dif-
fuse flow on the Aurora mound at ~3,888 m depth on the southern part of the Gakkel
Ridge (82.5°N). The biological communities are dominated by a new species of coccu-
linid limpet, two small gastropods, and a melitid amphipod. The ongoing analyses of
Aurora Vent Field samples will contribute to positioning the Gakkel Ridge hydrother-
mal vents in the global biogeographic puzzle of hydrothermal vents.