scholarly journals How does the Arctic affect North Atlantic climate? Fresh perspectives on a long-standing question.

2021 ◽  
Author(s):  
Marilena Oltmanns ◽  
N. Penny Holliday ◽  
James Screen ◽  
D. Gwyn Evans ◽  
Simon A. Josey ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Heat Waves ◽  
Rapid Change ◽  
The Arctic ◽  
Extreme Weather Events ◽  
Weather Extremes ◽  
Arctic Warming ◽  
The North ◽  
Arctic Ice

<p>Recent decades have been characterised by amplified Arctic warming and increased occurrence of extreme weather events in the North Atlantic region. While earlier studies noticed statistical links between high-latitude warming and mid-latitude weather extremes, the underlying dynamical connections remained elusive. Combining different data products, I will demonstrate a new mechanism linking Arctic ice losses with cold anomalies and storms in the subpolar region in winter, and with heat waves and droughts over Europe summer. Considering feedbacks of the identified mechanism on the Arctic Ocean circulation, I will further present new support for the potential of Arctic warming to trigger a rapid change in climate.</p>

scholarly journals CMIP5 Projections of Arctic Amplification, of the North American/North Atlantic Circulation, and of Their Relationship

2015 ◽  
Vol 28 (13) ◽  
pp. 5254-5271 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Lorenzo M. Polvani
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
Coupled Model ◽  
Arctic Region ◽  
The Arctic ◽  
Cmip5 Models ◽  
Arctic Amplification ◽  
Arctic Warming ◽  
The North ◽  
Sequence Of Events

Abstract Recent studies have hypothesized that Arctic amplification, the enhanced warming of the Arctic region compared to the rest of the globe, will cause changes in midlatitude weather over the twenty-first century. This study exploits the recently completed phase 5 of the Coupled Model Intercomparison Project (CMIP5) and examines 27 state-of-the-art climate models to determine if their projected changes in the midlatitude circulation are consistent with the hypothesized impact of Arctic amplification over North America and the North Atlantic. Under the largest future greenhouse forcing (RCP8.5), it is found that every model, in every season, exhibits Arctic amplification by 2100. At the same time, the projected circulation responses are either opposite in sign to those hypothesized or too widely spread among the models to discern any robust change. However, in a few seasons and for some of the circulation metrics examined, correlations are found between the model spread in Arctic amplification and the model spread in the projected circulation changes. Therefore, while the CMIP5 models offer some evidence that future Arctic warming may be able to modulate some aspects of the midlatitude circulation response in some seasons, the analysis herein leads to the conclusion that the net circulation response in the future is unlikely to be determined solely—or even primarily—by Arctic warming according to the sequence of events recently hypothesized.

Counting Harp Seals with ultra-violet photography

Polar Record ◽  
1976 ◽  
Vol 18 (114) ◽  
pp. 269-277 ◽  
Author(s):  
D. M. Lavigne
Keyword(s):  
North Atlantic ◽  
White Sea ◽  
North Atlantic Ocean ◽  
Ultra Violet ◽  
The Arctic ◽  
Hudson Bay ◽  
The North ◽  
Breeding Populations ◽  
Pagophilus Groenlandicus ◽  
Arctic Ice

The Harp Seal Pagophilus groenlandicus is a gregarious, migratory seal inhabiting Arctic and sub-Arctic waters of the North Atlantic Ocean. In spring, asthe ice recedes, the largest of three known breeding populations migrates up the east coas of Canada from the Gulf of St Lawrence, along the coast of Labrador, to the Canadian Archipelago, Hudson Bay, and the west coast of Greenland. After spending the summer feeding in Arctic waters, the seals move southward ahead of the Arctic ice pack, reaching the coast of Labrador and the Gulf of St Lawrence sometime in late December or early January. They reappear at the end of February and in early March in whelping ‘patches’ or concentrations on ice inthe Gulf of St Lawrence west of the Magdalen Islands, and off the coast of Labrador in an areaknown as the ‘Front’. One of the two smaller and probably distinct breeding populations is to be found in the White Sea, the other in the Vestisen [West Ice] between Jan Mayen and Svalbard.

Understanding the role of the troposphere in the surface impact of the 2018 sudden stratospheric warming event

2021 ◽  
Author(s):  
Juan J. González-Alemán ◽  
Christian M. Grams ◽  
Blanca Ayarzagüena ◽  
Pablo Zurita-Gotor ◽  
Daniela I. V. Domeisen Domeisen ◽  
...  
Keyword(s):  
North Atlantic ◽  
Vortex Breakdown ◽  
Rapid Change ◽  
Polar Vortex ◽  
The Arctic ◽  
Lead Times ◽  
Strong Impact ◽  
Ensemble Forecasts ◽  
Stratospheric Polar Vortex ◽  
The North

<p>Sudden stratospheric warmings (SSWs) are impressive phenomena that consist of a rapid stratospheric polar vortex breakdown. SSWs can have a strong impact on the tropospheric weather and are mainly associated with the negative phases of the Arctic and North Atlantic Oscillations (AO, NAO), and with northern European cold outbreaks, thus causing high societal impact. However, the mechanisms behind the downward impact from the stratosphere are insufficiently understood, especially the role played by the troposphere. In this work, we investigate this coupling and its associated predictability limits by studying the 2018 SSW event.</p><p>By analyzing ECMWF 15-day ensemble forecasts and partitioning them into different weather regimes, we search for possible dynamical tropospheric events that may have favored the downward stratosphere-troposphere coupling during and after the SSW. It is found that two cyclogenesis events were the main drivers of the negative NAO pattern associated with a Greenland Blocking, causing a rapid change from prevailing westerlies into a blocked state in the North Atlantic region. Unless these cyclogenesis events are simulated in the forecasts, the prediction of a Greenland Blocking does not become highly prevalent. No important stratospheric differences between WRs were found. A possible oceanic contribution to this blocked state is also found. This work corroborates that individual synoptic events might constitute a “predictability barrier" for subsequent forecast lead times. It also sheds light, on the specific topic of troposphere-stratosphere coupling.</p>

scholarly journals Freshening of the Labrador Sea as a trigger for Little Ice Age development

2016 ◽  
Author(s):  
Montserrat Alonso-Garcia ◽  
Helga F. Kleiven ◽  
Jerry F. McManus ◽  
Paola Moffa-Sanchez ◽  
Wallace Broecker ◽  
...  
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Little Ice Age ◽  
Meridional Overturning Circulation ◽  
Ice Age ◽  
Labrador Sea ◽  
The North ◽  
External Forcings ◽  
The North Atlantic ◽  
Arctic Ice

Abstract. Arctic freshwater discharges to the Labrador Sea from melting glaciers and sea-ice can have a deep impact on ocean circulation dynamics in the North Atlantic modifying climate and deep water formation in this region. In this study, we present for the first time a high resolution record of ice-rafting in the Labrador Sea over the last millennium to assess the effects of freshwater discharges in this region on ocean circulation and climate. The occurrence of ice-rafted debris (IRD) in the Labrador Sea was studied using sediments from Site GS06-144-03 (57.29° N, 48.37° W, 3432 m water depth). IRD from the fraction 63–150 µm show higher concentration during the intervals: ~ 1000–1100, ~ 1150–1250, ~ 1400–1450, ~ 1650–1700 and ~ 1750–1800 yr AD. The first two intervals occurred during the Medieval Climate Anomaly (MCA), whereas the others took place within the Little Ice Age (LIA). Mineralogical identification indicates that the main IRD source during the MCA was SE Greenland. In contrast, the concentration and relative abundance of hematite-stained grains (HSG) reflects an increase in the contribution of Arctic ice during the LIA. The comparison of our Labrador Sea IRD records with other climate proxies from the subpolar North Atlantic allowed us to propose a sequence of processes that led to the cooling events during the LIA, particularly in the Northern Hemisphere. This study reveals that the warm climate of the MCA may have enhanced iceberg calving along the SE Greenland coast and, as a result, freshened the subpolar gyre (SPG). Consequently, SPG circulation switched to a weaker mode through internal feedbacks that reduced convection in the Labrador Sea decreasing its contribution to the Atlantic Meridional overturning circulation and, thus, the amount of heat transported to high latitudes. This mechanism very likely preconditioned the North Atlantic inducing a state in which external forcings (e.g. solar irradiance and volcanic input) could easily drive periods of severe cold conditions in Europe and the North Atlantic like the LIA. The outcomes of this work indicate that a freshening of the SPG may play a crucial role in the development of cold events during the Holocene, which may be of key importance for predictions about future climate.

scholarly journals Using Bayesian Networks to investigate the influence of subseasonal Arctic variability on midlatitude North Atlantic circulation

2020 ◽  
pp. 1-46
Author(s):  
Nathanael Harwood ◽  
Richard Hall ◽  
Giorgia Di Capua ◽  
Andrew Russell ◽  
Allan Tucker
Keyword(s):  
Bayesian Networks ◽  
North Atlantic ◽  
Hidden Variables ◽  
Polar Vortex ◽  
The Arctic ◽  
Stratospheric Polar Vortex ◽  
Arctic Warming ◽  
The North ◽  
The North Atlantic

AbstractRecent enhanced warming and sea ice depletion in the Arctic have been put forward as potential drivers of severe weather in the midlatitudes. Evidence of a link between Arctic warming and midlatitude atmospheric circulation is growing, but the role of Arctic processes relative to other drivers remains unknown. Arctic-midlatitude connections in the North Atlantic region are particularly complex but important due to the frequent occurrence of severe winters in recent decades. Here, Dynamic Bayesian Networks with hidden variables are introduced to the field to assess their suitability for teleconnection analyses. Climate networks are constructed to analyse North Atlantic circulation variability at 5-day to monthly timescales during the winter months of the years 1981-2018. The inclusion of a number of Arctic, midlatitude and tropical variables allows for an investigation into the relative role of Arctic influence compared to internal atmospheric variability and other remote drivers.A robust covariability between regions of amplified Arctic warming and two definitions of midlatitude circulation is found to occur entirely within winter at submonthly timescales. Hidden variables incorporated in networks represent two distinct modes of stratospheric polar vortex variability, capturing a periodic shift between average conditions and slower anomalous flow. The influence of the Barents-Kara Seas region on the North Atlantic Oscillation is found to be the strongest link at 5- and 10-day averages, whilst the stratospheric polar vortex strongly influences jet variability on monthly timescales.

scholarly journals Radioisotope constraints of Arctic deep water export to the North Atlantic

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Lauren E. Kipp ◽  
Jerry F. McManus ◽  
Markus Kienast
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Deep Water ◽  
Particle Flux ◽  
The Arctic ◽  
Global Ocean ◽  
Central Basin ◽  
The North ◽  
Crucial Component ◽  
Global Ocean Circulation

AbstractThe export of deep water from the Arctic to the Atlantic contributes to the formation of North Atlantic Deep Water, a crucial component of global ocean circulation. Records of protactinium-231 (231Pa) and thorium-230 (230Th) in Arctic sediments can provide a measure of this export, but well-constrained sedimentary budgets of these isotopes have been difficult to achieve in the Arctic Ocean. Previous studies revealed a deficit of 231Pa in central Arctic sediments, implying that some 231Pa is either transported to the margins, where it may be removed in areas of higher particle flux, or exported from the Arctic via deep water advection. Here we investigate this “missing sink” of Arctic 231Pa and find moderately increased 231Pa deposition along Arctic margins. Nonetheless, we determine that most 231Pa missing from the central basin must be lost via advection into the Nordic Seas, requiring deep water advection of 1.1 – 6.4 Sv through Fram Strait.

Seasonal Sensitivity of the Northern Hemisphere Jet Streams to Arctic Temperatures on Subseasonal Time Scales

2017 ◽  
Vol 30 (24) ◽  
pp. 10117-10137 ◽  
Author(s):  
Elizabeth A. Barnes ◽  
Isla R. Simpson
Keyword(s):  
Time Scales ◽  
North Atlantic ◽  
North Pacific ◽  
Arctic Sea Ice ◽  
The Arctic ◽  
Jet Stream ◽  
Jet Streams ◽  
Near Surface ◽  
Arctic Warming ◽  
The North

Near-surface Arctic warming has been shown to impact the midlatitude jet streams through the use of carefully designed model simulations with and without Arctic sea ice loss. In this work, a Granger causality regression approach is taken to quantify the response of the zonal wind to variability of near-surface Arctic temperatures on subseasonal time scales across the CMIP5 models. Using this technique, a robust influence of regional Arctic warming on the North Atlantic and North Pacific jet stream positions, speeds, and zonal winds is demonstrated. However, Arctic temperatures only explain an additional 3%–5% of the variance of the winds after accounting for the variance associated with the persistence of the wind anomalies from previous weeks. In terms of the jet stream response, the North Pacific and North Atlantic jet streams consistently shift equatorward in response to Arctic warming but also strengthen, rather than weaken, during most months of the year. Furthermore, the sensitivity of the jet stream position and strength to Arctic warming is shown to be a strong function of season. Specifically, in both ocean basins, the jets shift farthest equatorward in the summer months. It is argued that this seasonal sensitivity is due to the Arctic-warming-induced wind anomalies remaining relatively fixed in latitude, while the climatological jet migrates in and out of the anomalies throughout the annual cycle. Based on these results, model differences in the climatological jet stream position are shown to lead to differences in the jet stream position’s sensitivity to Arctic warming.

scholarly journals North Atlantic freshwater events influence European weather in subsequent summers

2021 ◽  
Author(s):  
Marilena Oltmanns ◽  
N. Penny Holliday ◽  
James Screen ◽  
D. Gwyn Evans ◽  
Simon A. Josey ◽  
...  
Keyword(s):  
North Atlantic ◽  
Heat Waves ◽  
Sea Surface ◽  
Jet Stream ◽  
North Atlantic Current ◽  
The North ◽  
Freshwater Fluxes ◽  
The North Atlantic ◽  
Arctic Ice ◽  
Atlantic Current

Abstract. Amplified Arctic ice loss in recent decades has been linked to increased occurrence of extreme mid-latitude weather. The underlying dynamical mechanisms remain elusive, however. Here, we demonstrate a novel mechanism linking freshwater releases into the North Atlantic with summer weather in Europe. Combining remote sensing, atmospheric reanalyses and model simulations, we show that freshwater events in summer trigger progressively sharper sea surface temperature gradients in subsequent winters, destabilising the overlying atmosphere and inducing a northward shift in the North Atlantic Current. In turn, the jet stream over the North Atlantic is deflected northward in the following summers, leading to warmer and drier weather over Europe. Our results suggest that growing Arctic freshwater fluxes will increase the risk of heat waves and droughts over the coming decades, and could yield enhanced predictability of European summer weather, months to years in advance.

scholarly journals Mechanisms Governing the Development of the North Atlantic Warming Hole in the CESM-LE Future Climate Simulations

2018 ◽  
Vol 31 (15) ◽  
pp. 5927-5946 ◽  
Author(s):  
Melissa Gervais ◽  
Jeffrey Shaman ◽  
Yochanan Kushnir
Keyword(s):  
Ocean Circulation ◽  
North Atlantic ◽  
Sea Surface ◽  
The Arctic ◽  
Labrador Sea ◽  
Sea Surface Temperatures ◽  
Subpolar Gyre ◽  
The North ◽  
Surface Temperatures ◽  
The North Atlantic

A warming deficit in North Atlantic sea surface temperatures is a striking feature in global climate model future projections. This North Atlantic warming hole has been related to a slowing of the Atlantic meridional overturning circulation (AMOC); however, the detailed mechanisms involved in its generation remain an open question. An analysis of the Community Earth System Model Large Ensemble simulations is conducted to obtain further insight into the development of the warming hole and its relationship to the AMOC. It is shown that increasing freshwater fluxes through the Arctic gates lead to surface freshening and reduced Labrador Sea deep convection, which in turn act to cool Labrador Sea sea surface temperatures. Furthermore, the resulting changes in surface ocean circulation lead to enhanced transport of cooled Labrador Sea surface waters into the interior of the subpolar gyre and a more zonal orientation of the North Atlantic Current. As a result, there is an increase in ocean advective heat flux divergence within the center of the subpolar gyre, causing this warming deficit in North Atlantic sea surface temperatures. These local changes to the ocean circulation affect the AMOC and lead to its slowdown.

scholarly journals Urban Heat Islands and Thermal Comfort: A Case Study of Zorrotzaurre Island in Bilbao

2021 ◽  
Vol 13 (11) ◽  
pp. 6106
Author(s):  
Irantzu Alvarez ◽  
Laura Quesada-Ganuza ◽  
Estibaliz Briz ◽  
Leire Garmendia
Keyword(s):  
Thermal Comfort ◽  
Heat Waves ◽  
Urban Environments ◽  
Urban Heat Islands ◽  
Extreme Weather Events ◽  
Climate Index ◽  
Physiological Equivalent Temperature ◽  
Heat Islands ◽  
The North ◽  
The Impact

This study assesses the impact of a heat wave on the thermal comfort of an unconstructed area: the North Zone of the Island of Zorrotzaurre (Bilbao, Spain). In this study, the impact of urban planning as proposed in the master plan on thermal comfort is modeled using the ENVI-met program. Likewise, the question of whether the urbanistic proposals are designed to create more resilient urban environments is analyzed in the face of increasingly frequent extreme weather events, especially heat waves. The study is centered on the analysis of temperature variables (air temperature and average radiant temperature) as well as wind speed and relative humidity. This was completed with the parameters of thermal comfort, the physiological equivalent temperature (PET) and the Universal Temperature Climate Index (UTCI) for the hours of the maximum and minimum daily temperatures. The results demonstrated the viability of analyzing thermal comfort through simulations with the ENVI-met program in order to analyze the behavior of urban spaces in various climate scenarios.

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