Sea surface distribution of nitrous oxide and methane in European shelf seas and the Atlantic Ocean

Wager, Natalie (2015) Sea surface distribution of nitrous oxide and methane in European shelf seas and the Atlantic Ocean. Doctoral thesis, University of East Anglia.

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Abstract

Abstract
Human
activities,
including
intensive
agriculture
and
fertiliser
use,
are
altering
the
radiative
forcing
on
the
planet
by
increasing
the
amount
of
the
climatically
active
gases,
nitrous
oxide
(N2O)
and
methane
(CH4),
in
the
troposphere.
There
are
currently
uncertainties
in
quantifying
the
natural
sources
and
sinks
of
N2O
and
CH4
in
the
marine
environment.
This
thesis
presents
high-­‐resolution
surface-­‐ocean
and
atmospheric
data
for
N2O,
CH4,
CO2
and
CO,
collected
using
Integrated
Cavity
Output
Spectrometry
(ICOS,
Los
Gatos)
during
the
D366
(NW
European
shelf
seas,
June/
July,
2011)
and
Atlantic
Meridional
Transect
22
(Atlantic
Ocean,
October/November,
2012)
cruises.
Interpretation
of
the
N2O
and
CH4
datasets
revealed
that
shelf
seas
produced
a
greater
atmospheric
source
of
N2O
and
CH4
than
the
open
ocean.
Shelf
sea
surface
waters
were
slightly
supersaturated
in
N2O
at
102
%,
but
undersaturated
in
the
open
ocean
at
97
%,
acting
as
slight
atmospheric
sink.
The
cause
of
undersaturation
in
surface
waters
is
unclear,
but
may
be
attributed
to
seasonal
cooling
and
a
potential
microbial
N2O
consumption
pathway.
The
dominant
pathway
for
N2O
formation
in
the
open
ocean
is
nitrification.
Both
nitrification
and
denitrification
may
be
important
in
the
production
of
N2O
in
shelf
seas.
Vertical
mixing
processes
and
upwelling
influence
the
surface
concentration
of
N2O.
Surface
waters
in
the
shelf
seas
and
the
Atlantic
Ocean
were
supersaturated
in
CH4
at
118
%
and
107
%.
Methanogenesis,
which
occurs
within
anoxic
sediments
of
shelf
seas,
rivers
and
estuaries,
was
the
dominant
source
of
CH4
during
D366.
Freshwater
inputs
that
were
supersaturated
in
CH4,
and
a
fully
mixed
water
column
vertically
mixing
CH4
from
marine
sediments,
influenced
the
surface
concentration
of
CH4
in
shelf
seas.
In
the
open
ocean,
methanogenesis
occurs
in-­‐situ
in
the
surface
waters.
Seasons
influenced
the
surface
concentration
and
saturation
of
N2O
and
CH4,
with
sea
surface
temperatures,
seasonal
effects,
and
stratification
affecting
these
gases.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Environmental Sciences
Depositing User: Vailele Chittock
Date Deposited: 15 Jun 2016 13:29
Last Modified: 30 Sep 2018 00:38
URI: https://ueaeprints.uea.ac.uk/id/eprint/59358
DOI:

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