Oceanography | December 2022
observational efforts and techniques.
The presentations include both papers
and sidebars (short reports) that high-
light some of the research findings,
approaches, challenges, and outstanding
questions developed over the past decade.
Within the sea ice theme, Meier and
Stroeve summarize current trends in
sea ice concentration, age, and thick-
ness; snow depth; and melt and freeze-up
dates using satellite-borne passive micro-
wave sensors, and they consider the fac-
tors driving these trends. Holland and
Hunke provide an overview of current
and near-future sea ice models developed
for use in climate studies, discuss recent
advances for improving sea ice predict-
ability, and examine prediction consis-
tencies across many of these models.
Webster et al. illustrate the spatial and
temporal scales of sea ice variability and
discuss how this variability can com-
plicate the synthesis of ice observations
from disparate sampling methods. They
then discuss how combining observa-
tions across spatial and temporal scales
can resolve these complications and yield
a better understanding of Arctic sea ice
system behavior. Two sidebars comple-
ment these papers. Perovich describes
autonomous ice mass balance buoys that
collect time-series observations of snow
and ice accumulation and melt. He then
shows that in collocating these buoys with
other autonomous systems, an observa-
tional network of the atmosphere, ice,
and ocean is achievable. Kwok provides
an overview of the ICESat-2 altimeter’s
abilities to observe sea ice and continen-
tal ice sheets and to detect the topogra-
phy of the sea surface height field, which
reflects the ocean circulation.
Changing sea ice properties interact
with the Arctic Ocean’s physical ocean-
ographic regime consisting of water
masses, circulation, and mixing. Rudels
and Carmack discuss how these pro-
cesses, mediated by winds, the influx of
waters from the North Pacific and North
Atlantic Oceans, and the enormous cir-
cumpolar terrestrial runoff, influence the
basin’s stratification and the subsequent
export of Arctic Ocean waters into the
North Atlantic. Along the same vein, a
sidebar by Pnyushkov and Polyakov
details the recent history of changes in
North Atlantic-derived waters flowing
along the Eurasian continental slope and
their connection to lower latitude pro-
cesses. The extensive continental shelf
area of the Arctic Ocean receives a mas-
sive riverine sediment load that will
increase with climate warming and affect
biogeochemical processes. Kipp and
Charette’s sidebar describes how radium
isotopes are effective tracers of terrestrial-
derived elements and are used to mon-
itor alterations in the Arctic Ocean’s
chemistry. Von Appen et al. review the
geographical heterogeneity and impor-
tance of mesoscale (~10 km diameter)
eddies that influence basin dynamics and
much of the mass and material exchanges
between the continental shelves and
the deep basin. At even smaller scales,
Rippeth and Fine review turbulent mix-
ing in an increasingly ice-free Arctic
Ocean, and then discuss how this mix-
ing varies geographically, and its sensi-
tivity to the changing seasonal ice cycle.
Thomson et al. focus on the complex
air-ice-ocean feedback mechanisms that
drive autumn ice formation and discuss
the spring and summer preconditioning
processes that influence fall freeze-up.
The exchange of waters between
the North Atlantic and Arctic Oceans
influences
the
Atlantic
Meridional
Overturning Circulation (AMOC), which
plays an important role in global climate
and oceanic sequestration of CO2. Weijer
et al. review recent observational and
modeling efforts that advance our under-
standing of the impacts of the changing
Arctic Ocean on the AMOC and the effects
on the Arctic due to feedbacks from the
AMOC. Bacon et al. discuss how inverse
methods, when applied to long- term
measurements collected along the Arctic
Ocean’s maritime boundaries, can be used
to generate estimates of surface fluxes of
heat and freshwater, net biogeochemical
fluxes, and estimates of ocean water mass
transformation rates. The AMOC is also
influenced by fresh water discharged from
the Greenland Ice Sheet. A sidebar by
Wouters and Sasgen examines changes
in Greenland ice sheet mass from 2002 to
the present using data from the Gravity
Recovery
And
Climate
Experiment
(GRACE) and the GRACE-FollowOn