SUMMARY OF MAJOR FINDINGS
Bottom line
- Large amplitude Multi-Decadal Variability (MDV) with a 50-80 year cycle is documented in climate
variables of the Arctic and North Atlantic air-ice-ocean system [see Refs. 118-122, 124].
- MDV of the Arctic and North Atlantic are related [see Refs. 124,125].
Arctic
- Over the 20th century observational records, the arctic atmosphere is characterized by two warm
phases (1930-1955, 1989-present) and one cold phase (1960-1988) [see Ref. 119].
- Phases of MDV in SLP and SAT are out of phase with the peak of low pressure occurring 15 years
before peak of warm air temperatures [see Ref. 119].
- The polar amplification paradigm needs to be revised because MDV impacts the calculation of trends.
Taking MDV into account, the long-term temperature trend in the Arctic maritime stations is comparable
to the global trend (i.e. is not amplified) [see Ref. 120].
- Observations of ice thickness and ice area display the MDV signal [see Ref. 121].
- Increased (decreased) transport of warmer Atlantic Water into the Arctic is evident during warm
(cold) phases of MDV [see Ref. 122].
- The rate of ice melt/growth and/or ice/water outflow (not anomalous supply of terrestrial waters
or net precipitation) comprise the primary terms that influence Arctic Ocean freshwater storage anomalies
[see Ref. 126].
North Atlantic
- Both the upper 300 meters and the 1000-3000 meter layer of the North Atlantic display MDV but
they are out of phase. In recent years the upper layer is warming while the lower layer is cooling
[see Ref. 124].
- MDV is characterized by a single sign anomaly in the North Atlantic, whereas the pattern associated
with the long-term trend (anthropogenic and low-frequency variability) has spatial variability with
high-latitude (>50°N) cooling supporting weakening of the North Atlantic circulation [see
Ref. 125].
New questions that have arisen as a result of this research
- Why is the SLP low offset by ~15 years from SAT maximum in the Arctic?
- The NAO paradigm (e.g NAO is negatively correlated with Arctic SAT) does not always hold and the
phasing of when the paradigm applies or does not apply is related to MDV phasing. Why?
- What are the detailed mechanisms of how the North Atlantic and Arctic variability are connected?
- synchronous MDV in both North Atlantic and Arctic regions questions
advective nature of this variability. What are the forces driving these
coherent fluctuations over vast Arctic/North Atlantic areas?
- How much of MDV is due to natural causes and how much may be
explained by human-induced activities?
