Week 13 Coastal erosion

 Coastal erosion is a normal process of nature. However, the rate of coastal erosion, and the frequency and intensity of coastal flooding events, are now on the rise around the world due to the changing climate.

    The western Makran coast displays evidence of surface uplift since at least the Late Pleistocene, but it remains uncertain whether this displacement is accommodated by creep on the subduction interface, or in a series of large earthquakes.

    During the past 13,000 yr, the climate of the Makran region and the sea level have changed significantly, the Makran coast has experienced an active uplift, and large amounts of sediment have been transported to the Makran continental margin. Therefore, the Makran continental margin is a natural laboratory to study the role of climate change, sea level fluctuations, and tectonic uplift in the evolution of sedimentary systems on continental margins. 

    The coast of Makran is more susceptible to erosion due to the reduced vegetation, and coastal rivers were able to transport river sediments to the continent margin during the brief but intense winter rainfall periods, even under relatively dry climates. On the central coast of Makran, small watershed rivers also can transport fine-grained rocks from the coastal plain. Meanwhile, the wave erosion in the late Holocene was still very intense. The bay beaches along the coast usually crenulated following the dominating wave direction, which further proves the role of waves. A large number of faults along the coast of Makran cause the juxtaposition of units of different erodibility at the same structural level, and the differential erosion of waves brings a large number of sediments to the Makran continental margin and further forms a unique coastal geomorphology. Therefore, in the late Holocene, river sediments, wave eroded materials, eolian dust under arid conditions, and huge amounts of thick sediments deposited on the shelf during the early Holocene were potential sources of material for the continental slope environment. 

Coastal erosion and climate change: A review on coastal-change process and modeling | Ambio (springer.com)

jmse-09-00891 (2).pdf

(PDF) Holocene Sedimentary Record and Coastal Evolution in the Makran Subduction Zone (Iran) (researchgate.net)

Week 10 Extreme Wether

 

Extreme Weather Iran

    Scientists with the World Weather Attribution group analyzed three years of temperature and precipitation data and found that climate change contributed to extreme temperatures, which in turn made drought at least 25 times more likely in parts of Syria and Iraq, and over 16 times more likely in Iran. 

    The study shows how climate change is playing a role in one of the world’s worst humanitarian disasters, combining with political chaos and conflict to push people into hunger and forcing many to flee their homes.

    The country’s climate is mainly arid and semiarid, except the northern coastal areas and parts of western Iran. The climate is extremely continental with hot and dry summer and very cold winter particularly in inland areas. Apart from the coastal areas, the temperature in Iran is characterized by relatively large annual range, about 22°C to 26°C. The rainy period in most of the country is from November to May followed by dry period between May and October with rare precipitation. 

    The average annual rainfall of the country is about 240 mm with maximum amounts in the Caspian Sea plains, Alborz and Zagros slopes with more than 1,800 and 480 mm, respectively. Iran has climatological diversity with three types of climate: 1) dry and semi-dry climate: large parts of internal lands and southern border of Iran have this climate; 2) Mountainous climate, which itself is subdivided into two categories of cold and moderate mountainous climate; 3) Caspian climate: narrow and small area between Caspian Se and Alborz Mountain Belt with 600-2000 mm annual rain.

    The IPCC estimates an increase in temperature in the Middle East up to 2 °C in the next 15–20 years and over 4 °C by the end of the century. This fact is combined with a decline in precipitation by 20% (IPCC 2007; Elasha 2010). Hence, the Middle East countries are very vulnerable to facing climate change effects. Among the Middle East countries, Iran will experience an increase of 2.6 °C in mean temperatures and a 35% decline in precipitation in the next decades (NCCOI 2014). Hence, the climate change fact of Iran is more severe than the Middle East region.

    Several researchers have reported the heat waves will be increased (30%) by the end of the century for Iran and West Asia (Zhang et al. 2005; Rahimzadeh et al. 2009; IPCC 2012). Therefore, many reports observe a steady decline in annual rainfall (~ 30%) (Nazaripour and Daneshvar 2014). Spatial and temporal trend of precipitation has been widely studied in Iran by several researchers. The literature review revealed that two high mountain ranges of Zagros and Alborz in west and north, respectively, strikingly affect the temporal and spatial patterns of rainfall and temperature (Dinpashoh et al. 2004; Modarres and Sarhadi 2009; Tabari and Talaee 2011; Raziei et al. 2012; Soltani et al. 2012; Somee et al. 2012; Dinpashoh et al. 2014; Darand and Mansouri Daneshvar 2014; Darand et al. 2015; Zarenistanak et al. 2015; Ghalhari et al. 2016; Roushangar et al. 2018).

    For instance, Rainfall trends analysis of Iran using the Mann–Kendall test indicated a decreasing trend in annual and seasonal precipitation at stations mostly occurring in the northwest of Iran (Modarres and Sarhadi 2009). Similar research using the Mann–Kendall test showed a significant negative trend in annual precipitation series at Iran especially in the winter series (Tabari and Talaee 2011). Another research found a relatively regular year-round distribution of precipitation in the north of Iran, but an extreme concentration of precipitation in a few months of the year was detected for the southern country (Raziei et al. 2012). A noticeable decrease in the precipitation series has been indicated in northern Iran, which has temperate weather affected by Alborz Mountains and the Caspian Sea (Somee et al. 2012).

    Regionalization of precipitation regimes in Iran using principal component analysis and hierarchical clustering analysis revealed that the main precipitation regime is in the winter season. In some parts of southern and southeastern of Iran, more than half of the total precipitation occurs in the winter. With moving away from the mentioned regions to the north and the Caspian Sea coast, the contribution of autumn precipitation to total one becomes higher than winter precipitation. The precipitation regime of northwestern parts of Iran is classified in the spring season. The contribution of summer precipitation to total precipitation is noticeable in the southern parts of the Caspian Sea and Southeastern areas (Darand and Mansouri 2014). Spatial and temporal trend analysis of temperature extremes in Iran revealed that about 66% of the country has a significant positive trend in the frequency of hot days and nights, while about 40.9% and 68.5% have a significant decrease in frequency of cold days and nights, respectively.

An overview of climate change in Iran: facts and statistics | Environmental Systems Research | Full Text (springeropen.com)

The Implications of Climate Change in Iran — American Iranian Council (us-iran.org)